bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Sulfur Sublimators Used in the Colombian Flower Industry
Authors: Huertas José Ignacio , Rodríguez Julián D.
Published: November 2021

The Oidio is considered one of the strongest diseases that attack the rose plantations. To control it, different alternatives are used, being the most common the application of fine sulfur powder over the leaves of the plant. To spray these powder, it is used a sulfur sublimator which warms the sulfur by electrical resistors up to the working temperature, where the sulfur is melted and evaporation takes place. The evaporated sulfur condenses forming very fine particles, which are transported by the natural convective airflow inside the greenhouse. Finally the fine powder is uniformly distributed over the leaves of the rose plants.

Previous studies have found that the thermal efficiency of the commercial sulfur sublimators is less than 0.1% and that the use of these sublimators represent more than 60% of the total electrical consumption of the farm.

Analytical and experimental work was conducted in order to find the optimum working temperature and the appropriate geometry of high efficiency sublimators. The work involved the characterization of commercial sublimators and the development of a mathematical model to describe the evaporation phenomena in the sublimator. Results showed that the working temperature should be 220°C, the appropriate geometry should be similar to a jar, and that the maximum attainable thermal efficiency working at 220°C is ∼2%. Based on these results, 2 prototypes of sublimators were manufactured. The new sublimators showed efficiencies close to 1%.
The Bio-Fuel Boiler House Concept in the District Heating Applications
Authors: Dzierzgowski Mieczysław , Zwierzchowski Ryszard
Published: November 2021

The biomass boiler house concept in the district heating applications, both from technical and economical point of view is detailed analyzed to assure the most effective investment and future operation.

This paper is concerned with the application of the Bio-fuel Boilers (BfB) as a one of perspective way of the District Heating System (DHS) modernization programs in Poland. Considering use of bio-fuels, Poland has relatively big potential particularly in bio-mass. Appropriate bio-mass technology is mainly related to the potential and supply of the bio-mass in cosidered region of the country. Usually, due to supply of bio-fuel, bio-mass fired boiler house not exceeds 30–40 MW.

For the purpose of selection of appropriate type and capacity of the BfB for installation in the District Heating Plant (DHP), operational analysis of the DHS and investigation of possible implementation of the Thermal Energy Storage (TES) systems were performed. Also, investment costs for the BfB and the TES system application in the DHS were assessed.

Operational analysis of the DHS covered supply and demand side i.e., heat generation by the DHP and heat consumption by the consumers. Heat consumption analysis during summer season was carried out in order to increase operational efficiency of the BfB installations and for investigation of the TES systems application in the DHS.

Heat storage in the DHS and its influence on capacity and operation of the BfB was also investigated. Both, heat accumulation by the District Heating Network (DHN) and by the non-pressure TES system were analyzed.

Finally, results of calculation of the required capacity of the TES systems assuring continuous and efficient operation of the BfB installation in the DHS, especially during summer season were shown. Some advantages of the TES system implementation in the DHS in case where the BfB are applied in the DHP were presented as well.
Analysis of a High-Efficiency Natural Gas-Assisted Steam Electrolyzer for Hydrogen Production
Authors: Martinez-Frias Joel , Pham Ai-Quoc , Aceves Salvador M.
Published: November 2021

This paper presents a description and analysis of a high-efficiency hydrogen production system. The main component of the system is a novel steam electrolyzer. In conventional electrolyzers, oxygen produced from electrolysis is usually released into the environment. In this design, natural gas is used to react with the oxygen produced in the electrolysis, reducing reduce the chemical potential difference across the electrolyzer, thus minimizing electricity consumption. The oxygen produced from the electrolysis is consumed in either a total oxidation or a partial oxidation reaction with natural gas. Experiments performed on single cells shown a voltage reduction as much as 1 V when compared to conventional electrolyzers. A heat recovery system (heat exchangers and catalytic converter) has been incorporated to the electrolyzer to obtain a high efficiency hydrogen production system. Results from a thermodynamic analysis show up to 70% efficiency with respect to primary energy source.
Second Law Analysis of a Combined Cycle With Integrated Compressor Inlet Air Cooling
Authors: Razani A. , Patterson M. , Kim K. J.
Published: November 2021

A gas/ammonia combined cycle is proposed in which exhaust gases from a Brayton gas topping cycle are used to produce superheated ammonia in a Heat Recovery Ammonia Generator (HRAG). To increase the power of the gas turbine in the combined cycle, when the environmental air temperature is high, inlet air to the compressor is cooled in the evaporator of an ammonia refrigeration cycle added to the combined air/ammonia power cycle. In this integrated combined power cycle a small fraction of high-pressure ammonia liquid, from the exit of the ammonia pump, is used in the ammonia refrigeration cycle to cool the air. The second law analysis and optimization of the above combined cycle is presented. The effect of important system parameters on the irreversibility of components in the cycle and the exergy of exhaust streams are evaluated. Reasonable constraints for system components are assumed. The power and efficiency of the cycle are evaluated and their dependences on system parameters are presented.
Thermoeconomic Analysis of a Combined Cycle and an IRSOFC Plant and Carbon Exergy Tax Influence on Advanced Systems Economic Competitiveness
Authors: Santarelli M. , Calì M. , Borchiellini R.
Published: November 2021

In the paper, a Thermoeconomic Analysis of two advanced energy systems, using different procedures for the electric power generation, has been performed. The first system is a three pressure level combined cycle of 335 MW, with an electricity production efficiency in the order of 54%. The second system is a model of advanced plant of 142 MW proposed by Massardo, composed by a pressurised Internal Reforming Solid Oxide Fuel Cell (IRSOFC) combined with a Gas Turbine; the plant can reach efficiencies at the order of 70%. A preliminary exergy analysis has been performed, which has outlined the irreversibilities generation. Then, a Thermoeconomic Analysis, evaluating the unit exergetic cost and unit thermoeconomic costs of all the energy flows of the two plants has been done. The results in terms of unit thermoeconomic costs obtained have outlined that a typology of plant like the FCGT4 is not yet competitive in economic terms with the advanced combined cycle plants, even if it represents a new high-efficiency technology, and especially An effective method for the reduction of CO2 emissions. Therefore, the second aim of the paper is to utilise a procedure of evaluation of an economic penalty applied to the CO2 emissions: the Carbon Exergy Tax (CET), based on the Second Law efficiency of the plant. It is discussed how the use of CET can contribute to the promotion and adoption of an advanced energy system such as the FCGT4 plant, reducing its economic gap with a standard technology represented by the combined cycle plant.
Relationship Between Stress, Height, and Methods of Reproduction for Opuntia Covillea and Opuntia Parryi
Authors: Litkouhi Behrang
Published: November 2021

In this research project, two species of cacti are investigated for relationships between stress, height, and methods of reproduction. These two species are Opuntia covillea, which has flat cladodes, and Opuntia parryi, which has pencil type cladodes. In a previous study, certain relationships were found at the stem segment. The purpose of this study is to confirm those findings, in addition to presenting any new relationships between the factors listed above. Also, a detailed geometric analysis and modeling methodology will be presented. One important point from the last study is that cladodes under the influence of a normal stress (from their own weight) developed approximately two times as many lignified xylem cells on the tensile side than on the compressive side. This would perhaps suggest that these lignified xylem cells prevent failure when they experience tension. This finding, along with other information, allowed an analogy to be drawn up comparing stem segments of cacti to concrete beams, since it is also a property of concrete that it cannot withstand tensile forces if it is not reinforced. Another trend noticed in the last project is that taller cacti plants experience less stress per unit area than shorter plants. Therefore, taller plants have a better ability to hold on to terminal stem segments, and thus have a higher tendency of reproducing sexually. Short plants tend to lose their terminal stem segments into the ground and reproduce asexually through the growth of a new plant from the terminal stem segments.
Computational Fluid Dynamics Model Analysis of the Blood Flow in the Right Coronary Artery on the Beating Heart
Authors: Hayashi H. , Ohashi T. , Mori D. , Yamaguchi T.
Published: November 2021

It is very important to elucidate the specific mechanism for the formation, growth, and breakdown of coronary plaque, in order to diagnose and prevent ischemic heart disease, such as myocardial infarction. Coronary atherosclerotic plaque has some characteristic background conditions from a mechanical viewpoint. Of these, the beating motion of the heart wall on which the major coronary arteries are fixed is very interesting, due to its possible mechanical influence on the flow inside the artery, and hence on atherogenesis. This study conducted a computational flow dynamics (CFD) simulation using a simplified model of the right coronary artery, which deforms with contraction of the heart. The right coronary artery was modeled using an ordinary helix, whose torsion and curvature changed in time with the contraction and dilatation of the heart. The results are discussed with respect to local hemodynamics’ characteristics, particularly the wall shear stress distribution.
Modeling the Visco-Elastic Response of Bovine Liver Tissue
Authors: Moskowitz Aaron J. , Richards Michael S. , Taylor Larry S. , Lerner Amy L.
Published: November 2021

Liver tissue plays a role in many physiological systems and is characterized as a soft tissue. Changes in the perceived stiffness of the liver by palpation may indicate Cirrhosis or other liver ailments. New ultrasound techniques that use an applied force such as sonoelastography may aid physicians in diagnosis by providing a quantitative comparison of the mechanical properties for the tissue [1]. At this time, these mechanical characteristics remain to be fully defined. In this study, a four-parameter model composed of springs and dashpots has been used to describe the response of liver under unconfined creep compression tests.
Modeling the Dynamic Composition of Engineered Cartilage
Authors: Wilson Christopher G. , Kohles Sean S. , Bonassar Lawrence J.
Published: November 2021

Investigation of the mechanisms underlying scaffold degradation and neotissue synthesis is essential to understanding the mechanical and biological performance of engineered tissues. Modeling the dynamic composition of cell-polymer constructs may be useful in estimating the constructs’ long-term function. In this preliminary study, we identified potential mechanisms and developed mathematical models to describe scaffold mass loss and extracellular matrix synthesis for engineered cartilage.
Effects of Wall Shear Stress on the Expression of Occludin in Human Umbilical Vein Endothelial Cells
Authors: Brey Darren M. , Yang Xu , Keynton Robert S. , Rousse Thomas J. , Ehringer William D. , Alexander J. Steven
Published: November 2021

The most common cause for chronic term (> 30 days) failure of vascular bypass grafts is the rapid growth of underlying tissues within arteries called intimal hyperplasia (EH) [1]. IH has been found to primarily exist in low wall shear stress regions within distal anastomoses [2]; however, the exact mechanism by which shear stress induces IH has not been ascertained. We hypothesize that endothelial lining permeability is induced by wall shear stress during tissue reorganization such as occurs within vascular bypass constructs. Occludin is an adhesion protein that is actively involved in endothelial cell (EC) tight junctions, and thus, may effect EC layer permeability. To date, no studies have been conducted to determine the effect of wall shear stress on this adhesion protein. Therefore, the purpose of this study is to evaluate the role of wall shear stress upon the expression of occludin within cultured endothelial cells.
Shape Opimization of Femoral Components of an Artificial Hip Prosthesis Using the Three-Dimensional P-Version Finite Element Method
Authors: Higa Masaru , Nishimura Ikuya , Tanino Hiromasa , Mitamura Yoshinori
Published: November 2021

The three-dimensional shape optimization of cemented total hip arthroplasty (THA) was introduced in this paper. The P-version Finite Element Method (FEM) combined with an optimization procedure was used to minimize the peak stress in the bone cement near the tip of the implant. Six-design variables were used in this study. Each variable represents the dimension of the medial-lateral width and anterior-posterior width of the three levels (proximal, distal and middle) of cross sectional area of the prosthesis. The results of the design optimization showed considerable reduction in stress concentration compared to the initial design that is currently used clinically.
Mass Transport and Hydrodynamic Modelling for an Annular Flow Bioreactor
Authors: Curran Stephen J. , Black Richard A.
Published: November 2021

Traditionally, cells and tissue samples have been cultured in the static environment of the petri-dish but with recent rapid advances in tissue engineering science there comes the need for dynamic bioreactor environments where cells and tissues can be produced more efficiently, more economically and in greater quantities. To meet these demands, it is necessary to tailor a bioreactor that optimizes both the hydrodynamic environment and the mass transport capabilities that the cells experience.
Hybrid Adaptive Kalman Filter: Calibrating a Hemodynamic Model for Continuous Arterial Pressure Monitoring
Authors: Zhang Yi , Asada H. Harry
Published: November 2021

A Hybrid Adaptive Kalman Filter (HAKF), consisting of a continuous Standard Kalman Filter (SKF) and an intermittent Least Squares Parameter Estimator (LSPE), is proposed to calibrate the hemodynamic model for continuous arterial pressure monitoring. Simulations of the HAKF using a classic Windkessel model are carried out to prove the principle of the proposal.
Active Learning in Mechanics Courses in Biomedical Engineering
Authors: Livesay Glen A. , Dee Kay C. , Nauman Eric A. , Hart Richard T.
Published: November 2021

In the Fall of 1999, the Department of Biomedical Engineering at Tulane University significantly revised the undergraduate curriculum to both increase the biomedical engineering content and move this BMEN content earlier in the students’ BMEN career. A major component of this revision was the introduction of bridge courses designed to ‘bridge’ from traditional engineering topics to biomedical engineering topics in the major sub-disciplines within biomedical engineering -Bioelectronics, Bioelectricity, Cell & Tissue Engineering, Biomaterials, and Biomechanics.
Learning Modules for Biomechanics: Preliminary Experiences With the Vanth Engineering Research Center
Authors: Pandy M. G. , Petrosino A. J. , Chang C. C. , Karande T. , Barr R.
Published: November 2021

The mission of the VaNTH (Vanderbilt-Northwestern-Texas-Harvard/MIT) Engineering Research Center for Bioengineering Educational Technologies is to bring learning scientists, learning technology specialists, and bioengineering domain experts together to formulate and perform new research on how bioengineers learn, how knowledge in bioengineering is structured, and how to best integrate these findings for effective instruction. Our work has been greatly influenced by the incorporation of reports issued by the Committee on Developments in the Science of Learning along with the Committee on Learning Research and Educational Practice. The Committees were convened by the National Research Council, and the resulting publication by Bransford et al. [1] entitled How People Learn (HPL) has been the basis for the overarching framework to situate our research and instructional design activities.
Hands-on Approaches to Biomechanics Education in a Technologically Connected Classroom
Authors: Vashishth Deepak , George Winson , Smith Jennifer , Brunski John B. , Ostrander Lee
Published: November 2021

In contrast to the traditional classroom environment that promotes passive learning, the multimedia-based studio approach is considered to be a more effective tool for delivering course content as it increases active in-class involvement, teamwork experience and cooperative learning (Wilson 1994). More significantly, the studio environment provides a plethora of opportunities to include case studies that promote hands-on experience and problem-solving, illustrate real-life problems and increase student interest in the course content (Starrett and Morcos 2001). In general, engineering courses benefit from the availability of simulation and analysis software in a multimedia studio environment. Biomedical engineering courses including biomechanics, however, are not always amenable to simulation and often require the setting of complicated and expensive tests involving human subjects and hazardous materials. Furthermore, unlike traditional medical courses, biomedical engineering departments do not have extensive teaching laboratories and students have little or no clinical exposure.
The Role of Biomechanics in the Modern Biomedical Engineering Undergraduate Curriculum
Authors: Spilker Robert L. , Kamm Roger D.
Published: November 2021

During the Summer and Fall of 2000, the Whitaker Foundation engaged the biomedical engineering community in a curriculum assessment and vision exercise that included: collection and posting (www.Whitaker.org) of a curriculum database from departments and programs in bioengineering (note that within this document, bioengineering is understood to be synonymous with biomedical engineering); identification of key curricular topic areas and facilitators for each of these areas; posting of white papers by the facilitators; and a period of community comment. This activity culminated in the Whitaker Educational Summit, held in December 2000, at which representatives of virtually all US bioengineering departments and programs, numerous international participants, and those interested in establishing programs, gathered for a series of lectures and discussions on general topics in the undergraduate bioengineering curriculum, and for focused group discussions in each of the topic areas. Summary comments were prepared at that meeting by professional science writers and published at the Whitaker web site, and a period of comment followed. As facilitators for the area of biomechanics, and representatives of the US National Committee on Biomechanics, we offer a vision of biomechanics in the undergraduate bioengineering curriculum, and a set of recommendations that result from the. Whitaker process.
Oscillatory Bone Fluid Flow and its Role in Initiating Remodeling in the Absence of Matrix Strain
Authors: Qin Yixian , Saldanha Anita , Kaplan Tamara
Published: November 2021

Load-generated intracortical fluid flow is proposed to be an important mediator for regulating bone mass and morphology [1]. Although the mechanism of cellular response to induced flow parameters, i.e., fluid pressure, pressure gradient, velocity, and fluid shear stress, are not yet clear, interstitial fluid flow driven by loading may be necessary to explain the adaptive response of bone, which is either coupled with load-induced strain magnitude or independent with matrix strain per se [2]. It has been demonstrated that load-induced intracortical fluid flow is contributed by both bone matrix deformation and induced intramedullary (IM) pressure [3]. To examine the hypothesis of fluid flow generated adaptation, it is necessary to test the mechanism under the circumstances of solely fluid induced bone adaptation in the absence of matrix deformation. While our previous data has demonstrated that bone fluid flow and its associated streaming potential product can be influenced by the dynamic IM pressure quantitatively [4], the objective of this study was to evaluate fluid induced bone adaptation in an avian ulna model using oscillatory IM fluid pressure loading in the absence of bone matrix strain. The potential fluid pathway was measured in the model.
Non-Invasive NMR Characterization of Cortical Bone Microdamage
Authors: Ni Qingwen , Nicolella Daniel P.
Published: November 2021

Bone damage occurs as a result of repetitive loading in-vivo [1] and has been implicated as a contributing factor governing bone fragility in diseases such as osteoporosis and in repetitive loading injuries such as stress fractures. In response to damage or microcracks in-vivo, healthy bone will self-repair by removing the damaged bone and replacing it with newly formed bone [2]. However, when the rate of damage accumulation is greater than the rate of repair in healthy bone, a fracture may result.
Measurment of Broadband Ultrasound Attenuation Using Tone Burst Frequency Scanning in Trabecular Bone Property Assessment
Authors: Lin Wei , Rubin Clinton , Qin Yixian
Published: November 2021

Osteoporosis is characterized by the non-traumatic fracture due to the deterioration of bone properties. Although there is a consensus that the loss of bone mass is the key factor to osteoporosis, the bone material strength and trabecular architecture are also important in the contribution to the whole bone strength. Ultrasound is mechanical in nature and it has the potential to assess the bone density as well as its mechanical stiffness. Ultrasound attenuation is one of the ultrasound parameters used to assess bone properties. Studies have shown that ultrasound attenuation is dependent on bone density [1,2] and is also indicative to the strength of trabecular bone [3,4]. Therefore, ultrasound attenuation has the potential to reveal bone properties. The objective of this study is to develop a frequency scanning method that can better extract the information of not only the bone quantity but also the bone quality.
Biomechanichal Comparison of Multilevel Cervical Laminectomy and Spinous Process Splitting Laminoplasty With or Without Hydroxyapatite Spinous Process Spacers
Authors: Kubo Shinichiro , Goel Vijay K. , Jo Yang S. , Hyun Kim J. , Tajima Naoya
Published: November 2021

Laminoplasty or laminectomy may is used for the treatment of multilevel cervical myelopathy. However, it has been shown that multilevel laminectomies can lead to segmental instability, kyphosis, perrineural adhesions and late neurological deterioration. [1–4] On the other hand, laminoplasty, seems to preserve motion, and reduces adjacent segment degeneration in a patient. [5–7] The role of biomechanical factors in the differences in outcome for the two procedures is not fully delineated. Our hypothesis is that laminoplasty procedure does not lead to an increase in motion while laminectomy does. An in vitro investigation was undertaken to test this hypothesis.
Relationships Between Transfemoral Socket Interface Pressure and Hip Moment of Residual Limb With a 4-Bar Pneumatic Knee During Stance Phase of Gait
Authors: Hong Jung Hwa , Ryu Jei Cheong , Kim Shin Ki , Mun Mu Seong
Published: November 2021

For transfemoral amputees, the biomechanical interaction between the stump and the prosthetic socket during stance phase of gait is critically important to achieve normal-like ambulation. It is widely accepted that abnormal socket interface pressure distribution and temporal behavior cause pathology in the stump directly affecting gait of amputees. Therefore, many investigators have studied static and dynamic socket pressure behaviors. The results of the investigations suggested that the pressure changes during gait of transfemoral amputees are closely related to the prosthetic alignment, the socket shape, the stump size, and the residual muscle activity [1,2]. In addition, the temporal changes of hip moment during ambulation may affect the socket pressure distributions of transfemoral amputees [3,4]. However, relationships between the hip moment and the socket pressure have not been well understood. The purpose of this study is to investigate the relationships between the hip moment and the socket pressure during amputee gait with transfemoral prostheses.
Femorotibial Articulation: 3-D Morphometry and Contact Analysis
Authors: Nuño N. , Ahmed A. M.
Published: November 2021

Numerical models of the knee joint are being increasingly used to study the internal mechanics of the joint, both in its intact condition and prosthetically resurfaced state. However, formulation of such models demands a precise knowledge of the complex three-dimensional shape of the articulating surfaces of the joint.
Precise Quantitative Models of the Equine Articular Carpus Anatomy and Contact Areas
Authors: Koff Matthew F. , Gardner Thomas R. , Balaguer Eric , Kawcak Chris , McIlwraith C. Wayne , Mow Van C.
Published: November 2021

Osteochondral diseases occur within ail bones and cartilages of the equine carpus and can lead to loss of athletic use and occasionally catastrophic injury that necessitate euthanasia. The intensity and direction of stresses that lead to such injuries are unknown. Joint modeling is a commonly used technique in human orthopaedic research that allows investigators to determine the internal stresses of joints. Through the use of computer models, various scenarios, such as ligament damage, can be simulated and changes in the resulting joint surface stresses determined [1]. The purpose of this study was to experimentally obtain precise quantitative contact area data of the articular surfaces of the distal radius, the proximal and distal aspects of the radial carpal bone and the proximal aspect of the 3rd carpal bone of the equine carpus. These data provide normative contact and cartilage thickness values for the equine carpus that will facilitate the use of this joint as a large animal model for osteoarthritis studies. Furthermore, these experimental data will serve as the basis for the development and calibration of an equine carpus whole joint computer model.
Comparison of Ground Reaction Force and Leg Muscle Activities During Tai Chi Movement and Normal Walking
Authors: Wu Ge , Liu Wei , Lansky Becky , Hitt Juvena
Published: November 2021

Osteoporosis increases with age. It is a major cause of mortality, morbidity, and medical expense worldwide [1]. It has been shown that increased activity level is associated with decreased osteoporosis [1–4]. These activities include walking, running, weight lifting, or Tai Chi [2–5]. However, it is not clearly known yet what characteristics of these exercises would best stimulate the growth of bone mineral density (BMD). Some believe that it is the fast rate of loading to the lower extremity during heel strike that best stimulates growth of BMD [4], some believe it is the peak loading to the lower extremity during stance [6], and some believe it is the level of muscle activation during weight bearing [7].
Development of an In Vivo Rabbit Model for Cartilage Trauma: Influence of Impact Stress Magnitude on Chondrocyte Death
Authors: Milentijevic Dejan , Liew Allan , Torzilli Peter A.
Published: November 2021

Joint injuries in humans are frequent and similar to those seen in all mammalian species. The most commonly used method to study the correlation between trauma and cartilage survival (post-traumatic arthritis) has been conducted using in-vivo animal models. In a majority of these animal models a single or multiple impact was delivered to the patello-femoral joint (PFJ) using a drop tower type apparatus [1–6]. A main limitation of these models is with the drop tower itself and the impaction of a “whole joint”. A free-falling mass impacting the specimen abruptly decelerates, generating a nonlinear inertial force upon the tissue due to cartilage’s structural non-homogeneity. Haut et al. [2] specifically commented that it was difficult to control the impact stress using a drop tower apparatus. In addition, the rate of loading is difficult to control because changes in potential energy will generate different stress magnitudes and rates of loading. Thus, it is hard to correlate these high-loading rate experiments to slow loading rate experiments [6,7]. Only one study reported exposing and directly traumatizing the articular surface of the joint, but again utilized a drop tower device [4,5]. All these studies correlated “impact energy” or “impact force” to the amount of cartilage damage but did not evaluate the influence of stress magnitude or the rate of loading.
Hydrodynamic Pressurization of a Trapped Lubricant Pool Between a Rippled Rigid Indenter and an Elastic Layer: An Investigation Into the Role of Surface Roughness on Cartilage Lubrication
Authors: Basalo Ines M. , Ateshian Gerard A.
Published: November 2021

In recent studies of articular diarthrodial joint lubrication, it has been proposed that hydrostatic pressurization of the cartilage interstitial fluid upon joint loading contributes significantly to the load support across the articular layers, thus reducing frictional forces and wear [1–3]. This boundary contact mechanism for porous media can explain the observed time-dependent response of the frictional coefficient. Nevertheless, alternative hypotheses have been also proposed which attribute the low friction coefficient to hydrodynamic lubrication [4]. In our recent analysis of a mixed lubrication problem where a lubricant pool is trapped between a rippled rigid indenter and a biphasic cartilage layer [5], it was observed that the hydrostatic pressurization of the trapped lubricant can enhance the fluid load support to a certain extent, but typically for a short duration on the order of 1 s only, until the lubricant is depleted by flowing into the cartilage layer. Furthermore, under steady-state sliding, it was found that a lubricant pool could not be sustained due to lubricant depletion. These analyses employed an inviscid model for the lubricant as they focused on hydrostatic pressurization only. In the current study, we investigate whether lubricant viscosity, which can promote hydrodynamic pressurization, might further enhance the fluid load support mechanism or alter the conclusions gathered from our earlier studies. To investigate these fundamental mechanisms, an elastic layer is used instead of a biphasic layer at first; a more elaborate biphasic analysis could be employed subsequently if warranted by the current findings.
A Real-Time Approach to Modeling Soft Tissue Deformation
Authors: Mayrose James , Chugh Kevin , Kesavadas T.
Published: November 2021

We are working toward developing a physically accurate real-time abdominal palpation simulator. To achieve this, two major goals must be met. The first is to develop a model that accurately simulates the physical characteristics of the tissues in the human abdomen. The model must not only be physically accurate, it must run in real-time for the simulation to be usable. The second major goal is to design a framework within which to parameterize physical properties of different tissues as well as a methodology to extract those parameters non-invasively.
A Device for Driving a Wire or a Drill Precisely in a Given Direction Through a Point Under Closed Sky Conditions
Authors: Danieli Guido A. , Fragomeni G. , Giuzio E.
Published: November 2021

The paper presents a new device which allows the precise positioning of a guide through a point and in a given direction, or which can permit to reach a given bone section. Other devices exist mainly addressed to the insertion of a screw in the correct position on endo-medullary nails, but these are usually based on the knowledge of the geometry of the nail, and are therefore made by the maker of the nail. In other instances, often the doctors use trial drilling under fluoroscopy to place a kirshner wire in the required position. The actual device is instead based only on an aiming methodology resting on geometrical considerations. Previous knowledge of the position of such a point and direction, which can be given by a hole belonging to a plate or to an endo-medullary nail or can be part of the patient’s bone structure, is not necessary. This is due to the use of fluoroscopy coupled to the localisation of two aiming planes on whose interception is placed the line of interest. A first instrument developed on this principle found limited clinical success due to the complexity of the first kinematic chain used in the aiming process and to human error. A new version has been designed and is at present under construction, which solves the kinematic problem through a careful choice of a series of constraints enabling the aiming process to be divided in sub processes, thus gradually controlling the final result.
Repeatability of a Computer-Aided Optical Tracking System for Total Knee Replacement Surgery
Authors: Sarin Vineet K. , Pratt William R. , Stulberg S. David
Published: November 2021

The success of total knee replacement surgery depends critically on the restoration of limb alignment and on proper implant positioning [1]. Even with contemporary mechanical alignment instrumentation, errors in alignment correction and implant positioning do occur [2–5]. To improve upon the accuracy of conventional mechanical instrumentation, computer-aided navigation systems have been developed for total knee replacement surgery. Clinical studies have demonstrated that use of these systems for knee replacement surgery can lead to improved limb alignment and implant positioning [6–9]. While such systems have been shown to be clinically effective, their overall accuracy and repeatability in clinical use appears to be highly technique dependent [10]. The inherent repeatability (precision) of such systems has not been closely investigated.
Design and Performance of a Surgical Tool Tracking System for Minimally Invasive Surgery
Authors: Brown Jeffrey D. , Rosen Jacob , Longnion Jeff , Sinanan Mika , Hannaford Blake
Published: November 2021

Minimally invasive surgery (MIS) is a technique introduced in the mid-1980s in which a few small incisions are made to allow for insertion of surgical tools and a camera through gasketed ports. Smaller incisions speed patient recovery times and lessen the chance of infection. They also introduce new interfaces as compared to more traditional open surgical techniques. These interfaces impose motion constraints and forces on the tool(s) and hand(s). These interfaces are not well characterized, yet surgical simulators and surgical robots are being developed without this vital information.
Development of an Input Interface Using Ocular Potential for Handicapped Users of Health Care Supporting Computer
Authors: Mizuno F. , Harada A. , Yamaguchi T.
Published: November 2021

Numerous attempts to adapt multimedia communication to medical care have been reported recently. It is our view that spiritual support is more important in medical care, while so-called high technology may be necessary for medical practice. Therefore, we proposed the concept of the Hyper Hospital [1–3], to offer patients a means of effective human communication during medical care. The Hyper Hospital is a medical system constructed on a computer and multimedia based-network, which patients use to participate in medical and care activities through improved communication media. It is sometimes difficult for physically handicapped patients, such as PMD (progressive muscular dystrophy), ALS (amyotrophic lateral sclerosis), and traumatic cervical injury patients, to operate a computer, because of their disabilities. Therefore, there is a serious digital divide between physically disabled patients and healthy people. To remedy this, various communication devices, such as those using winking, eye gaze, voice, and electrical biological signals (event-related potential [4–5], electrooculogram, etc.) have been proposed and tested. These are designed to enable seriously handicapped patients to use a computer without using the usual mechanical input devices, such as a keyboard, mouse, or joystick. Although an EEG (electroencephalogram) offers one source of such potential electrical biological signals, it produces a very weak electrical signal that contaminating noise makes difficult to process. On the other hand, the ocular potential generated by the dipolar potential of the eyeball has a much larger gain in potential than the EEG. Moreover, the ocular potential can be easily controlled by the user, and eye-movement ability remains largely intact, even after neurological diseases progress to a very advanced stage. Therefore, this report studied the development of an input interface for computers using an electrooculogram.
Engineering Analysis of an End-Release Safety Belt Buckle
Authors: Syson Stephen R.
Published: November 2021

A typical end-release safety belt buckle has been analyzed to determine its failure modes. These failure modes were evaluated based on crash test, sled test and component test data. A verification of the hypothesized failure modes was found in the patent literature. The component tests that were conducted confirmed the hypothetical failure modes and verified that the failures could and would occur in real world collisions as well as testing.
Potential Benefits of Adhesive Airway Mucus
Authors: Krumpe Peter , Evrensel Cahit A.
Published: November 2021

What possible benefit could there be to sticky respiratory mucus? Most of the clinical efforts of respiratory therapy are aimed at thinning thick mucus and decreasing its adhesivity to the airway walls. Yet evidence has accumulated that thinning airway mucus may contribute to dependent atelectasis and may worsen respiratory failure in ventilated patients. We speculate that mucus adhesivity benefits cough clearance by keeping mucus in central airways where cough velocity can clear it, rather than allowing backsliding of mucus due to gravity that would result in distal plugging. It follows that mucus in central airways would benefit from increased adhesivity while mucus in distal airways would not.
Platelet Activation in Flow Past Mechanical Heart Valves
Authors: Bluestein Danny , Jesty Jolyon , Saltman Adam E. , Krukenkamp Irvin B. , Suresh Krishnamurthy
Published: November 2021

Numerical studies, in vitro, and in vivo measurements were conducted, aimed at quantifying free emboli formation and procoagulant properties of platelets induced by flow past mechanical heart valves (MHV). Pulsatile turbulent flow simulation was conducted past a St. Jude medical MHV in the aortic position, to study the effects of valve implantation technique on the thromboembolic potential of the valve. A misaligned valve with subannualarly sutured pledgets produced accelerating jet flow through the valve orifices and a wider wake of shed vortices. Shear stress histories of platelets along turbulent trajectories exposed the platelets to elevated shear stresses around the leaflets, leading them to entrapment within the shed vortices. In vitro platelet studies were conducted past the MHV mounted in a recirculation flow loop, by measuring the platelets ability to support the activation of acetylated human prothrombin by factor xa, which enables sequestering flow induced effects and quantification of the platelets activity state. The platelet activation state increased monotonically as a function of the recirculation time past the valve, as measured by the thrombin generation rates in the assay. Finally, platelet activity state measurements were conducted in vivo, from a sheep with an implanted MHV, showing marked increase of platelet activation after valve implantation.
An Automated Methdology for Investigating the Correlation Between Abdominal Aortic Aneurysm Wall Stress and Risk of Rupture
Authors: Raghavan Madhavan L. , Fillinger Mark F. , Marra Steven P. , Kennedy Francis E.
Published: November 2021

Clinical experience with regard to predicting abdominal aortic aneurysm (AAA) rupture has shown that although AAA diameter is a good indicator, there are likely other risk factors. Some researchers have explored a biomechanical approach to predicting aneurysm rupture risk [1,2] based on the hypothesis that aneurysm rupture occurs when the mechanical stresses in the aortic wall exceed the wall failure strength. Therefore, knowledge of wall stresses in a particular AAA may help identify impending rupture. Recently, researchers have used patients’ abdominal CT scan data and blood pressure to estimate in-vivo AAA wall stresses [3]. In the present project, an improved automated methodology is used to predict AAA wall stress. The underlying correlation between mechanical stress and aneurysm wall rupture is also investigated.
Effect of Variations in Intraluminal Thrombus Constitutive Properties on Abdominal Aortic Aneurysm Wall Stress: A Parametric Study
Authors: Di Martino Elena S. , Wang David H. J. , Redaelli Alberto , Makaroun Michel S. , Vorp David A.
Published: November 2021

The prevalence of abdominal aortic aneurysm (AAA) is growing together with population age, being 8.8% in a population above 65 years according to a recent study [1]. Deciding between elective surgical repair of AAA and watchful management is a complex issue due to the lack of reliable rupture risk indices. The maximum transverse diameter of AAA is most commonly used in clinical practice to base this decision. From a biomechanical viewpoint, AAA rupture is related to the balance between the stresses acting on the wall and strength of the wall tissue. Many different factors contribute to the stress within the aortic aneurysm wall, including the presence of intraluminal thrombus (ILT) [2–5], the local surface curvature [6] and material characteristics of the AAA wall [7], and the presence of local “stress concentrators” due to calcifications or local thinning. As regards the ILT, its role with respect to aneurysm wall stresses has given rise to many hypotheses. Some studies show that the pressure inside the thrombus is not reduced with respect to the arterial blood pressure, some, including studies from the authors, state a possible protective role [2–5]. Previously in our laboratory, a nonlinear, hyperelastic constitutive model was developed for ILT, and the parameters for which were determined through ex-vivo experimentation [8]. The purpose of this study was to investigate the reliability of using the same population-mean values of ILT constitutive parameters for estimates of wall stress distribution in all AAA. For this, we performed a parametric study in which the ELT constitutive parameters were varied within a physiological range and aortic wall stresses were evaluated.
3-D Simulation for Blood Flow and Artery Compression in Asymmetric Stenotic Arteries With Axial Stretch
Authors: Tang Dalin , Yang Chun , Kobayashi Shunnichi
Published: November 2021

There has been increasing evidence that severe stenosis may cause artery compression and plaque cap rupture leading to heart attack and stroke. The physiological conditions under which that may occur and mechanisms involved are not well understood. It has been known that severe stenosis causes critical flow and wall mechanical conditions such as flow limitation, flow separation, low and oscillating shear stress distal to the stenosis, high shear stress and low or even negative flow pressure at the throat of stenosis, artery compression or even collapse. Those conditions are related to limitation of blood supply, intimal thickening and thrombosis formation, endothelism damage, platelet activation and aggregation, plaque cap rupture (for review, see [1,2]). Due to the complexity of the problem and lack of experimental data for mechanical properties of arteries under both expansion and compression, previous models were limited primarily to flow behaviors and with various limitations (axisymmetry, rigid wall, small strain, small pressure gradient). In this paper, experimental data for artery mechanical properties under physiological conditions were measured and a 3-d computational model is introduced to investigate flow behaviors and wall stress and strain distributions with fluid-structure interactions to better understand the mechanism involved in artery compression and plaque cap rupture.
Designing Intravascular Stent: A Computational Study
Authors: Migliavacca Francesco , Petrini Lorenza , Colombo Maurizio , Auricchio Ferdinando , Pietrabissa Riccardo
Published: November 2021

Intravascular stents are small tube-like structures placed into stenotic arteries to restore blood flow perfusion to the downstream tissues. The first implanted stent was first described by Dotter [1] to treat arterial shrinkage, but the clinical routine implantation began in the 1990s to improve the limitations of balloon angioplasty, such as restenosis and abrupt closure. If compared to angioplasty, stent higher efficiency is supported by randomized trials and clinical studies. Nevertheless, problems and difficulties remain, such as migrations, collapses, cloth formation or positioning difficulties (flexibility, trackability, etc...). In other words, although intravascular stents are nowadays routinely and successfully used, research and development are still necessary, to improve the design and to avoid the long-term failure.
Improved Histologic Analysis of Component Distribution and Wall Behavior in Cyanoacrylate-Embolized Vessels
Authors: Calvo William J. , Lieber Baruch B. , Wakhloo Ajay K. , Hopkins L. Nelson
Published: November 2021

Use of embolic agents is currently an accepted treatment modality among neurointerventional clinicians in order to completely occlude abnormal shunts in the cerebral vasculature known as arteriovenous malformations or AVMs. The first cyanoacrylate polymer recently approved by the US Food and Drug Administration for use in humans is n-butyl 2-cyanoacrylate (NBCA). In order to control the polymerization time of NBCA, as well as to opacify the mixture for angiographic visualization, an iodized poppyseed oil-based contrast agent (Lipiodol) is added to the NBCA. Glacial acetic acid is also used to delay polymerization further by decreasing the pH of the mixture.
Quantification of Diastolic Viscoelastic Properties of Isolated Cardiac Muscle Cells
Authors: Baicu Catalin F. , Zile Michael R.
Published: November 2021

Pathological processes which cause diastolic congestive heart failure (CHF), such as pressure overload hypertrophy (POH), produce abnormalities in the material properties of cardiac muscle cells (cardiomyocytes) and may selectively alter its elastic stiffness, viscosity, or both. Previous methods used to characterize these cardiomyocyte viscoelastic properties were constrained by specific biological and engineering limitations, which prevented testing in conditions that mimic normal physiology. The current study proposes an uniaxial variable-rate stretching method, in which isolated cardiomyocytes embedded in a three-dimensional gel matrix were subjected to stretch. Physiological Ca++ (2.5 mM) and rapid stretch rates up to 100 μm/sec provided experimental conditions parallel to in vivo physiology. The proposed method identified and individually quantified both cellular stiffness and viscosity, and showed that POH increased both elastic and viscous cardiomyocyte diastolic properties.