bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytoskeleton Rearrangement in Activated Human Neutrophils
Authors: Alteraifi Abdullatif M. , Zhelev Doncho V.
Published: July 2023

The crawling of the neutrophil is essential for its physiological and pathological activity. The neutrophil crawls by projecting pseudopods in the direction of a higher chemoattractant concentration in a process known as chemotaxis. In this process, the cell initially adheres tightly to the present substrate and then rearranges its cytoskeleton. Finally, the ceil body contracts, which results in cell movement. The rearrangement of the cytoskeleton is believed to be a crucial component of cell motility (Cunningham et al., 1992) which determines the overall rate of crawling (Zigmond, 1993). Therefore, it is important to find means of characterizing this in different conditions in order to reveal the role of the different factors in neutrophil motility. The available assays for studying neutrophil motility has one common disadvantage namely, they all produce large contact areas between the cell and the supporting substrate. This large contact area can be coupled with adhesion, which may alter neutrophil activation. To avoid the creation of large contact area with the cell surface in our experiments, we used micropipets. The use of micropipets allow both to minimize the contact area and to manipulate the cellular environment. Using this technique we can produce single pseudopods on individual cells by delivering a known concentration of a chemoattractant to the cell surface. We use the chemoattractant N-formyl-methionyl-leucyl-phenylalanine (fMLP) and by employing the above technique we were able to produce highly oriented cylindrical pseudopods on initially passive neutrophils (Fig. 1). Also, by using another micropipet assay (Zhelev and Hochmuth, 1995) we produced pseudopod-like structures in chemoattractant free solution, by pulling a tether from the cell surface (Fig. 2). In both cases we observe the formation of a dense F-actin network next to the leading edge of the pseudopod or pseudopod-like structure. Also, when the pseudopod or the pseudopod-like structure extends away from the cell body we observe the cell granules penetrating the network region. This penetration shows that there are vacancies in the network region, which indicate network depolymerization. The depolymerization of the network provides conditions for actin turnover (Theriot and Mithchison, 1991).
Concentration of Therapeutic Agents in Neoplasm
Authors: Rooney Frank , Sarntinoranont Malisa , Ferrari Mauro
Published: July 2023

One of the principal objectives of researchers in cancer treatment is to increase the fraction of chemotherapeutic molecules that reaches primary or metastatic malignancies. One possible avenue towards this goal is the coupling of the drug molecule with agents capable of identifying neoplasms, as is typically done with antibody-antigen complexation. While this has had some success, even a perfectly antibody guided therapeutic agent encounters significant complications in reaching the targeted neoplasms. Since these problems are mainly mechanical rather than biological in nature they cannot be dealt with by better biomarker technology. Jain and his coworkers have identified several such obstacles to delivery among them being the blood viscosity and the high interstitial pressures within tumors.

The analysis of Jain et al relates to large tumors and thus may not be appropriate to answer some of the questions of the clinical oncologist. In particular, the assumption that the fluid pressure is time independent limits the scope to large, slowly growing, dominantly necrotic tumors. Though the time scale for convection/diffusion of the macromolecules is very short compared to the typical doubling times for tumors, the assumption of time independence of the fluid pressure is in general not tenable since the pressure varies widely through the growth of the tumor and in particular depends on the tumor growth rate and the absence or presence of a necrotic core. In order to calculate the penetration properties of a chemotherapeutic agent, i.e. the concentration of drug in a tumor, we have used poroelastic constitutive assumptions together with spherical symmetry to obtain a pressure distribution that varies with the tumor’s age. Using this, we can obtain concentration profiles for the early stages of growth of the neoplasm. In fact, we show in Fig. 1 that in the initial growth phase of the tumor the concentration profile rises at first before decreasing with increasing age since the interstitial pressure is not high enough yet to act as a significant barrier to the delivery of the drug.

At present there is a lack of modeling in the area of drug distribution in cancer tumors. Developing better models is important because of their potential as quantitative tools in clinical oncology. Issues such as proper drug dosage, the timing of the insertion and the course of delivery (Fig. 2) are all features of a good model that could guide a practitioner in his work. Our model determines the tumor response as a function of it’s age and also the point at which convection no longer occurs in the majority of the tumor. The model could conceivably be used to determine when this type of therapy is no longer effective, thus saving medical resources and unnecessary chemotherapy side effects for patients.
Oscillatory Flow in a Flexible Curved Tube
Authors: Fujioka Hideki , Oka Kotaro , Tanishita Kazuo
Published: July 2023

The axial dispersion in the High frequency oscillation (HFO) occurs due to the interaction between radial mixing and radially-nonuniform axial velocity profile. The secondary flow works as the lateral mixing in the curved portion of pulmonary bifurcation. Pedley and Kamm (1988) identified the significant effect of curvature on the gas dispersion, and discovered the convective resonance phenomena which gives a highly-peaked local maximum of axial gas transport when the secondary flow circulation time becomes identical to the cycle period. Subsequently Sharp et. al. (1991) experimentally confirmed the presence of convective resonance in a fully developed oscillatory flow in a curved tube. Dragon and Grotberg (1991) presented the effect of wall flexibility on axial mass transport in an oscillatory flow through a infinitely long straight tube. They showed the effective diffusivity, Deff, diminished for all values of α, but Deff attained a local maximum in the HFO range, that coincided with a minimum phase angle between the wall position and the axial flow. Therefore the interaction between the wall and the fluid through a complex airway structure significantly influences the velocity profiles and gas dispersion. In the present study, we performed the numerical simulations of fully developed oscillatory flow through a curved tube with elastic wall in order to investigate the effect of wall flexibility on the secondary flow.
The Advancement of Theoretical Cord Mechanics to Be Used in Tendon and Ligament Research
Authors: Stuckey Jon I. , Conway Ted A.
Published: July 2023

With the ever evolving research in the mechanical identities of live tissues, further development in the area of theoretical cord mechanics is necessary in order to model such structures as tendons and ligaments. The major disadvantage with the current status in cord mechanics is that it is only possible to analyze a helically wound structure, such as a tendon or ligament, if the geometrical attributes of the material are known. This disadvantage can be overcome if a technique can be developed to optimize the geometrical properties of a material by knowing the material properties, the available force in the deflected structure, the design stress for the model, and the bending moment. Geometric optimization will develop by, in essence, deriving the theory of cords in reverse.
Correlation of Wrist Ligamentotaxis With Carpal Distraction During External Fixation
Authors: Loebig Thomas G. , Badia Alejandro , Baratz Mark E. , Anderson Donald D.
Published: July 2023

Distraction of the wrist via external fixation is used to effect and protect the reduction of distal radius fractures by applying tension to the wrist ligaments, a principle known as ligamentotaxis. Wrist and finger stiffness has been associated with overdistraction of the wrist through external fixation (Kaempffe, 1993; Sanders, 1991). A decrease in the range of motion at the metacarpophalangeal (MP) and proximal interphalangeal (PIP) joints has been shown to occur as distraction increases (Moran, 1992). Empirically proposed guidelines for attaining adequate distraction (Agee, 1994; Seitz, 1993) have not been experimentally substantiated. We tested uninjured cadaver wrists to correlate progressive tension across the wrist with associated carpal distraction. To provide a clinically useful method to assess ligamentotaxis, we evaluated the relationships between separation of joint spaces, applied distraction, and the tension carried across the wrist.
Poroelastic Properties of Vertebral Trabecular Bone
Authors: Lim Tae-Hong , Hong Jung Hwa
Published: July 2023

Bone is a composite material consisting of a porous solid phase (mineralized bone tissue) and a fluid phase (blood, marrow, and interstitial fluid). The fluid in bone is known to perform complex functions such as a transport medium biologically as well as the bone remodeling processes. The presence of moving fluid in bone is postulated to contribute to the energy absorbing properties and time-dependent behavior of bone. In numerous studies, the theory of poroelasticity has been used to simulate the bone behavior incorporating the fluid flow in bone. Results of these analytical studies demonstrated the significance of including fluid phase in the studies of bone mechanics. Limitations in these studies, however, are the use of assumed values of poroelastic properties of bone and the lack of experimental validation of their model predictions.
Variationally Derived 3-Field Lagrange Multipler and Augmented Lagrangian Poroelastic Finite Elements for Soft Tissues
Authors: Levenston Marc E. , Frank Eliot H. , Grodzinsky Alan J.
Published: July 2023

Among the approaches to quasistatic poroelastic finite element analyses of soft tissues, the most common versions are 2-field u-w or u-U penalty or “mixed-penalty” formulations (Simon, 1992; Suh et al., 1991; Spilker and de Almeida, 1992) and 2-field u-π or u-p mixed formulations (Simon, 1992; Wayne et al., 1991). The field designations refer to solid (or bulk) displacements u, fluid displacements w or U, and pressures π or p. Although they avoid the numerical ill-conditioning typical of penalty formulations, the u-π and u-p formulations are sub-optimal in that the fluid fields must be derived from the solid and pressure fields. Recently, an infinitesimal strain, constant permeability 3-field mixed u-p-U approach was shown to avoid many of the difficulties of the 2-field penalty and mixed formulations for dynamic soil mechanics applications (Gajo et al., 1994).
Tissue Engineering: The Next Generation of Medical Implants
Authors: Nerem Robert M.
Published: July 2023

The engineering of living tissue, i.e. tissue engineering, involves the use of living cells, manipulated through their extracellular environment or even genetically, to develop biological substitutes for implantation into the body and/or to foster the remodeling of tissue in some other active manner (1). The purpose is to either repair, replace, maintain, or enhance the function of a particular tissue or organ. For some organs, the first step will be extracorporeal devices; however, the long term goal of tissue engineering should be either implantable systems or the in vivo remodeling of tissue. Because there are not enough organs available for transplantation to meet the needs of the individuals on waiting lists, there is a real need for tissue-engineered biological substitutes.
In Vivo Strains in Bone Near Transcortical Implants
Authors: Hiatt Mark J. , Lin Yuan , Powers Dennis L. , Gharpuray Vasanti M.
Published: July 2023

Transcortical implants have been used by numerous investigators to evaluate the response of cortical bone to various implant materials. The experimental model involves drilling holes through the cortex of a long bone of the experimental animal and then placing cylindrical implants or “plugs” of the test material in the drilled holes. The implants are retrieved after a predetermined period of implantation, and the bone/implant interface is assessed either mechanically, using the push-out test, or histologically to determine the response of bone to the material. Conclusions are then drawn as to the suitability of the material for implant applications. However, different researchers have reported a wide range of results from experiments designed to measure the response to apparently similar implant materials (Black, 1989).
Compliant Effect on the Axial Gas Transport in Model Airway
Authors: Inaba Yasuo , Fujioka Hideki , Oka Kotaro , Tanishita Kazuo
Published: July 2023

Many studies on the high-frequency oscillation dealt with the gas transport in a model human airway and pointed out that the axial gas transport is affected by various factors; geometries, tube compliance, the presence of surfactant and others. Particularly Grotberg et al. (1991) theoretically revealed that the role of tube compliance gives a major effect on the axial gas transfer. However, no experimentally reveal the compliant effect on the gas transport in a symmetrical bifurcation, being regarded as a model human airway.
The Stabilty of One-Dimensional Flow in a Finite Collapsible Tube
Authors: Walsh Colin , Fricker Arnaud , Casteret Jerome
Published: July 2023

Flow-induced oscillation of collapsible tubes provides a model for clinical events such as wheezing (Grotberg 1994). Corresponding theories are sought to gain physiological insights. However, such theories use highly simplified analyses. For instance, flutter models of wheezing all assume an infinite length tube (Grotberg and Reiss 1984; Grotberg and Shee 1985; Webster, Sawatzky, Hoffstein, LeBlanc, Hinchey, and Sullivan 1985), and cannot assess the role of inlet and outlet conditions. Below, we give preliminary results dealing with this finite length issue.
In Vitro Evaluation of Combined Cardiac Stenotic and Regurgitant Valve
Authors: Einav S. , Zaretsky U. , Keren G. , Sherez J.
Published: July 2023

The simplified Bernoulli equation may not accurately calculate pressure gradient across the valve in combined aortic stenosis and regurgitation (Cujec, 1992 and Stewart, 1991). The specific aim of this project is to investigate in a pulse duplicator system the pressure and flow changes for a caged and tilting disk aortic valve with combined lesions and to correlate parameters derived from Continuous wave and Color Doppler flow mapping to hemodynamic measurements. The various severity of valve insufficiency and/or stenosis were simulated. Parameters, obtained by Doppler measurements, should be corrected in case of combined aortic valve lesions to avoid incorrect diagnosis. Degree of insufficiency in the stenosed valve influenced pressure gradient. Area of regurgitant jet depends on stenosis severity as well.
Experimental Measurement of Impact Force at Valve Closure of a Tilting Disc Mechanical Heart Valve
Authors: Cheon Gill-Jeong , Lee Jeong-Han , Chandran K. B.
Published: July 2023

Impact forces and strain induced on the guiding struts due to impact between the disc and the struts during the opening and closing phases were measured with a Björk-Shiley monostrut valve in a pulse duplicator simulating physiological pulsatile flow. The maximum impact force imparted on the valve housing during the closing phase of the valve was measured to be 25N for a range of aortic pressures between 13.3 to 21.3 kPa (100 to 160 mm Hg). The maximum value of impact forces on the inlet and outlet struts computed from the force equilibrium were found to be 17N and 9N respectively. However the maximum strain and stress of 2.4 × 10−4 m/m and 47 MPa respectively were measured at the root of the outlet struts, while the strains and stresses at the roots of the inlet strut were negligible. The results of such measurements may be extended for the analysis of the endurance limit and optimal design of the components of a mechanical valve.
The Use of Bioactive Glass Particles As Microcarriers
Authors: Ducheyne Paul , Gao Hongxia , El-Ghannam Ahmed , Shapiro Irving , Ayyaswamy Portonovo
Published: July 2023

Among the various materials that affect bone cell function, and therefore, could serve as the microcarrier material, bioactive glass has been our material of choice. In the early seventies, Hench et al.[1] formulated these glasses with a typical composition of 45% SiO2, 24.5% Na2O, 24.5% CaO and 6% P2O5 (by weight). They documented that upon implantation in bone tissue, this glass called bioactive glass 45S5, firmly adhered to bone. By now, at least nine groups from around the world have shown that glasses typically containing 40–60 mole % SiO2 and various amounts of Na2O, CaO, P2O5 and some smaller amounts of other oxides bond to bone tissue. As the glass is immersed in vivo, bodily fluids cause the glass to corrode. This corrosion results in selective leaching of sodium ions, the formation of a silica gel layer, and eventually the formation of a calcium phosphate rich layer. It is a recent finding that bioactive glass, when made in granular form with a narrow size range (300–355 μm), has the unique capacity to cause differentiation of osteoprogenitor cells to cells expressing the osteoblastic phenotype [2]. This property of upregulating stromal osteoprogenitor cells to osteoblasts in vivo, as well as the capacity to enhance the expression of the osteoblastic phenotype in vitro, form the basis for our selection of bioactive glass 45S5 as the carrier of choice for culturing typical bone tissue cells in microgravity environment.
Development of a Cytoindentation Theory and Experiment for Obtaining Cell Biomechanical Properties
Authors: Shin Daehwan , Athanasiou Kyriacos
Published: July 2023

It is well known that cells respond to mechanical stimuli by altering their biochemical activities. To understand this phenomenon, termed mechanotransduction, it is necessary to quantify cellular stress-strain relationships. Various experiments have been developed in the literature to measure mechanical characteristics of cells. The most widely used technique involves micropipette aspiration to characterize flaccid cells in suspension. The areal modulus of an erythrocyte (Evans and Hochmuth, 1976) and the viscoelastic constants of leukocytes (Schmid-Schönbein et al, 1980) were measured using this technique. More recently “cell poking” was developed (Zahalak et al, 1990) to measure the stiffness and shear modulus of leukocytes. The objectives of our study were to develop a cytoindentation apparatus, experiment, and theoretical model to obtain the intrinsic material properties of the individual cell attached on a substrate.
A Biomechanical Investigation Into the Effects of Overuse Coupled With Intrinsic or Extrinsic Modifications on Rotator Cuff Tendons
Authors: Flanagan Colleen L. , Soslowsky Louis J. , Carpenter James E. , Thomopoulos Stavros , Yian Edward H.
Published: July 2023

One of the most common soft tissue injuries of the musculoskeletal system is injury to the rotator cuff tendons of the shoulder joint. These injuries often limit physical activity (workplace or athletic) and subsequently have a significant impact. Thus, knowledge concerning the etiology and pathogenesis of this condition is important.
Computational Simulations of the Flow Convergence Method for the Quantification of Mitral Regurgitation: Comparison of Fluent and CFD-ACE
Authors: Hopmeyer Joanne , Wilkerson Patrick W. , Levine Robert A. , Yoganathan Ajit P.
Published: July 2023

Mitral regurgitation is a disease of the left side of the heart in which the mitral valve does not close completely during ventricular contraction, causing a jet of blood to be ejected back into the left atrium. The non-invasive quantification of mitral regurgitation is an important but elusive clinical goal and the flow convergence method has shown promise in the assessment of this disease. [1,2]
The Use of Multivariate Johnson Distributions to Model Trunk Muscle Coactivation
Authors: Mirka Gary A. , Glasscock Naomi F. , Stanfield Paul M. , Psihogios Jennie P.
Published: July 2023

A model for predicting trunk muscle coactivation patterns is developed in this research. Electromyographic (EMG) data from ten trunk muscles were collected from 28 subjects as they performed simulated lifting tasks. Nine repetitions of each combination of independent variables were performed by each subject. Included in these exertions were asymmetric postures and dynamic (isokinetic and constant acceleration) exertions. The muscle activity data collected during these trials were used to develop marginal distributions of trunk muscle activity as well as a 10 × 10 correlation matrix that describes how these muscles cooperate in the development of these trunk extension torques. These elements were then combined to generate multivariate distributions describing the coactivation of the trunk musculature.
The Influence of Biochemical and Morphological Constituents of Human Bone on Microdamage
Authors: Yeni Yener N. , Brown Christopher U. , Norman Timothy L.
Published: July 2023

Bone microdamage as a result of normal cyclic loading is believed to be a factor in cortical bone fractures. Evidence exists that an increase in the amount of microdamage results in a decrease in the ability of bone to resist fracture (Brown et al., 1996). Osteon morphological constituents including Haversian canals, cement lines, osteon size, and density have been proposed to play a role in microdamage initiation and propagation. Haversian canals were proposed to act as stress concentrators and therefore crack initiators whereas cement lines were believed to serve as crack arrestors (Burr et al., 1988; Wang and Norman, 1996).
The Effect of Ilio-Tibial Band Load on the Stress Distribution Pattern in a Human Femur With Hip Stem
Authors: Shareef Nazeer H. , Levine Danny L.
Published: July 2023

A clear understanding of the strength, deformation characteristics and stress distribution pattern in human femur due to the joint and muscle forces will help in increasing the reliability of total hip replacement performance through improvement in design. Experimental as well as analytical techniques have been used by researchers (Rybicki et al. 1972, Wood et al. 1973, and Mcleish et al. 1973) to study the biomechanical behavior of the human femur.
Residual Strain Effects on the Stress Field in a Thick Finite Element Model of the Human Carotid Bifurcation
Authors: Delfino A. , Stergiopulos N. , Moore J. E. , Meister J.-J.
Published: July 2023

A three-dimensional finite element model of the carotid artery bifurcation was constructed to determine the effects of prestrain on the stress field. The model takes into account the variation of the thickness along the bifurcation and the material is considered to be hyperelastic, incompressible, homogenous and isotropic. The results demonstrate that when prestrain is taken into account the distribution of principal stress along the inner wall and the circumferential stress throughout the wall is much more uniform than in a model without prestrain. The differences are most significant at the apex.
On the Nonlinear Bi-Directional Friction Properties of the Bone-Implant Interface
Authors: Hashemi A. , Shirazi-Adl A. , Dammak M.
Published: July 2023

In cementless implants, the friction at the bone-implant interface plays an important role in the mechanical response of the system, particularly in the immediate post operative period when no bony ingrowth has yet occurred. Uni-directional friction properties at the interface between various porous- and smooth-surfaced metals and tibial cancellous bone have previously been measured [1,2]. In contrast to the idealized Coulomb’s friction law, nonlinear tangential load-displacement relations were found at the interface. These studies [1,2], however, treated the friction at the bone-implant interface only in one direction. In a 3-D contact situation, the articulating bodies undergo relative movements and develop shear forces in different directions on the common interface. The objectives of the current study are, therefore, set as: (a) to measure the nonlinear bi-directional friction properties of the porous coated metal-cancellous bone interface, and (b) to develop proper constitutive equations required to be implemented in the subsequent realistic finite element studies of knee joint cementless replacement systems.
Role of Facet Articulation in Mechanics of the Lumbar Spine: Significance of Facet Gap Distance
Authors: Shirazi-Adl A.
Published: July 2023

Articulation between different bodies is a common phenomenon in the human musculoskeletal joints. Proper consideration of contact is of prime importance in biomechanical studies of such structures. An example is the facet joints that are known to play a significant role in spinal mechanics. While stiffening and stabilizing the spine, the facet joints degenerate and could be a source of the low-back pain. A number of experimental and numerical model studies have identified the load-bearing characteristics of the facet joints in lumbar motion segments under various loads. In this study, the mechanical role of facet joints in a model of the whole human lumbar spine is studied under different single and combined loads. This is done directly by computing the contact loads on facets in an intact lumbar spine or indirectly by removing the facet joints at a level and analysing the perturbed condition. In particular, the effect of facet gap distance on facet loads at different levels and on the lumbar mechanics is studied by altering the gap limit distance below which contact initiates. It is demonstrated that the interference gap distance between adjacent facets is of primary importance in the effectiveness of lumbar facet joints under different loads.
Contact Stresses in a Joint After Hemiarthroplasty
Authors: Bonavito Nino L. , Gharpuray Vasanti M.
Published: July 2023

Hemiarthroplasty is an attractive alternative to total joint arthroplasty, and is used (in particular in the hip or the shoulder) when one side of the joint remains relatively healthy (Cofield, 1991, Chao et al., 1991). Its major advantages over total arthroplasty are that less foreign material is implanted into the body, and that less bone is removed from the joint. However, the procedure also has several drawbacks that are associated with the increase in contact stresses at the metal-cartilage interface and the resulting deterioration of the cartilage. Replacement of the bearing surface only, with a polymer component to reduce contact stresses introduces the problems of fatigue failure due to large cyclic stresses. It has been previously hypothesized that the use of a compliant coating with a metal backing would reduce contact stresses, and lower the high factional torque seen in an all-metal system (Feinberg and Fleming, 1987). However, the modulus mismatch between the metal backing and the coating may cause interfacial debonding induced by shear stresses.
A Testing Apparatus for Cervical Load Simulation of C1-C2 Transarticular Screw Fixation Techniques
Authors: DiAngelo Denis J. , Jansen Thomas H. , Eckstein Eugene C. , Dull Scott T. , Foley K. T.
Published: July 2023

Transarticular screw fixation is an accepted surgical treatment for pathologic C1-C2 instability due to trauma, ligamentous laxity or degenerative disorders. A testing apparatus and protocol were developed to replicate the physiologic loading at the C1-C2 transarticular surfaces and evaluate different transarticular fixation techniques. The testing system’s utility was demonstrated through trials on two surgical screw types with equal length but different root diameters. The screws with the smaller root diameter (i.e., lesser mechanical integrity) required only a small number of cycles before breakage occurred by a bending fatigue mechanism but served adequately when used with a modified Brooks construct.
Mechanical and Dimensional Adaptation of Rabbit Carotid Artery Cultured In Vitro
Authors: Matsumoto Takeo , Okumura Eijiro , Miura Yuichiro , Sato Masaaki
Published: July 2023

Hypertension causes various changes in the artery wall, both morphologically and mechanically. Many of these responses can be viewed as adaptation process of soft tissues to increased load. For example, wall thickening may be caused by a mechanism maintaining intramural hoop stress at a constant level; decrease in the incremental elastic modulus compared at the same pressure suggests the restoration of elastic properties at physiological condition (Matsumoto and Hayashi 1994). These changes are, however, also attributable to other factors such as hormonal changes and altered nervous stimuli. For example, it has been reported that renal hypertension causes wall thickening of femoral artery even if its pressure was kept normal by aortic coarctation (Liu et al., 1988). It is very difficult to exclude such factors as long as mechanical adaptation is studied in vivo. In this study, we excised arterial segments, cultured them under controlled mechanical conditions, and observed changes following the culture.
Finite Element Analysis of Endovascular Graft Within the Diseased Aorta
Authors: Oh Seik , McIntyre John P. , Rhee Richard , Peterson Robert C.
Published: July 2023

Nonlinear finite element methods were used to analyze the plastic deformation of an endovascular graft stent and the interaction of the graft and the aortic wall. The stent was collapsed to the size of the catheter shaft and then re-expanded within the aorta to its original size. Interaction between the stent and the aortic wall was also simulated to determine the contraction force of the aortic wall when the stent distends the pressurized aorta. The compression force is regarded as the holding force of the graft positioned within the aorta. Stress, strain and deformation of the stent were obtained as a result and compared to the material strength for the determination of the stress failure with fatigue effects.
The Advantage of Robot-Assisted Knee Positioning for ACL Reconstruction Surgery
Authors: Sakane M. , Li G. , Fox R. J. , Woo S. L.-Y. , Rudy T. W. , Livesay G. , Fu F. H.
Published: July 2023

The goal of ACL reconstruction surgery is to restore normal ligament function and knee kinematics. Multiple factors can contribute to its outcome. Studies using cadaveric knees have been conducted to examine the effect of surgical variables on ACL reconstruction (1–3,7). However, large inter-specimen variability, less-than-reproducible surgical techniques, difficulties in data collection, and so on have made it difficult to determine the effect of these surgical variables independently. In this study, we studied the effect of knee positioning during ACL reconstruction on in-situ graft force and anterior tibia displacement of the knee when subjected to anterior tibial load. We hypothesize that a robot-assisted positioning of a knee to its initial/intact state should result in better outcomes (5) when compared with the conventional (empirical) positioning by a surgeon.
Mild/Moderate Sprains Do Not Decrease Ligament Strength: A Theoretical Model
Authors: Crisco Joseph J. , Panjabi Manohar M.
Published: July 2023

Unlike complete ligament ruptures, there is limited information on the injury and healing mechanisms of mild and moderate ligament sprains. These sprains comprise 85% or more of all ligament injuries. Previously we studied the effects of sprain (subfailure) injury on the in vitro mechanical properties of the rabbit anterior cruciate ligament (Panjabi et al., 1996). Stretching the ACL to 80% of the peak load increased subsequent deformations and decreased stiffness below 80%, but had no effect on any mechanical properties above 80%, including the peak load and its deformation. The purpose of this study was to develop a theoretical model that was capable of testing the hypothesis that subfailure loading sufficient to produce partial damage/injury does not decrease the peak load of a ligament.
Models for Lateral Dispersion in Flowing Blood: A Sequence Random Walks of Increasing Descriptive Power
Authors: Eckstein Eugene C.
Published: July 2023

Random walks of increasing complexity are related to models that depict dispersion in shear flows of concentrated suspensions, especially blood.
Applications of Geometric Models in Orthopaedics
Authors: MacWilliams B. A. , Barrance P. J. , Chao E. Y. S.
Published: July 2023

Dynamic models of musculoskeletal joint systems developed from images of human specimens have many potential applications in orthopaedic research. Such models may be used for dynamic analysis, load/deformation and stress/strain of bone implant systems studies, and pre-treatment planning in orthopaedic surgery and rehabilitation. The models, the graphic database, and the simulation/animation software also serve as valuable educational tools to demonstrate the functional anatomy of musculoskeletal joint systems.
Intravascular Ultrasound in Imaging Diseased Arteries
Authors: Back Martin R. , White Rodney A.
Published: July 2023

Development of miniaturized piezoelectric transducers positioned at the end of intraluminal catheters have allowed high resolution, ultrasonic imaging of various cardiac, vascular and hollow organ structures. Current intravascular ultrasound (IVUS) catheters provide real-time, luminal and transmural cross-sectional imaging in large vessels with dimensional accuracy. Present applications of IVUS include imaging in arterial occlusive disease, aneurysms and traumatic injuries. Intravascular ultrasound can delineate wall morphology, lesion shape, volume and length and branch configurations. Concomitant rapid expansion of minimally-invasive endovascular therapies in coronary and peripheral vasculature have added new role for IVUS. In addition to diagnostic information, IVUS enables choice of appropriate angioplasty technique, endovascular device guidance and controlled assessment of the efficacy of interventions. Real time IVUS imaging can only be utilized during invasive diagnostic and therapeutic procedures after vascular access is established. Further acceptance and implentation relies upon the effectiveness of IVUS in improving endovascular outcomes and minimizing periprocedural complications as compared to alternative imaging modalities.
Heat Transport in the Perpendicular Direction of Superlattices and Periodic Thin-Film Structures
Authors: Chen G.
Published: July 2023

Superlattices consisting of alternating layers of extremely thin films often demonstrate strong quantum size effects, which have been utilized to improve conventional devices and to develop new ones. The interfaces in these structures also affect their thermophysical properties through reflection and transmission of heat carriers. This work studies heat transport in the direction perpendicular to the film plane of superlattices and other periodic thin-film structures. Starting from the Boltzmann transport equation (BTE) and the first law of thermodynamics, boundary conditions based on diffuse interface scattering are established. Further treatment of the BTE leads to a set of integral equations describing the distribution of temperature gradient within each layer and thermal boundary resistance at interfaces. Numerical solution of these equations yields the temperature distribution and the thermal boundary resistance in the structure. Results show that the effective thermal conductivity of the structure in the perpendicular direction is controlled by both the size effects on heat transfer within each layer and the thermal boundary resistance between different layers. The thermal boundary resistance is no longer an intrinsic property of the interface but also depends on the layer thickness as well as the phonon mean free path. Comparison of the model predictions with available experimental data is favorable but also indicates the need for further theoretical and experimental studies.
Micromechanical Thermal Sensors for Gas Parameters Measurements
Authors: Frolov Gennadiy A. , Gendin Alexandr V. , Grudin Oleg M. , Katsan Ivan I. , Krivoblotskiy Sergey N. , Lupina Boris I.
Published: July 2023

Micromechanical thermal sensors for flow/pressure drop and gas heat capacity measurements are described. They are based on a unified sensing element containing 150 nm thick silicon nitride membrane with Ni thermoresistors placed on it. Electronic circuits of the sensors and experimental results in a wide range of flows arc presented. Thermal flow sensor has linear response in a four orders range and detects as small flow and pressure drop as 7·10−6 ml/s and 10−3 Pa. Thermal analysis and pilot tests of heat capacity sensor were performed. It is experimentally shown that small air density variations of about 2·10−7 gcm−3 caused by 0.2 mm Hg absolute pressure changes can be detected.
Heat Transfer From a Flush-Mounted Heat Source-Limiting Cases and the Conjugate Peclet Number
Authors: Cole K. D.
Published: July 2023

This study of a flush-mounted heat source on a flat plate cooled by a steady flow provides a new perspective on the electronic cooling problem by identifying the conditions under which the full conjugate analysis may be replaced by simple limiting cases. The three limiting cases discussed are fluid-only analysis, lumped-wall analysis, and solid-only analysis. The numerical results are obtained from integral equations based on Green’s functions, and the results are presented in a compact form with the use of the conjugate Peclet number, kf/ks(Pe)1/3. The results are also compared to experimental data from the literature.
Experiments and Simulations on a Micro-Mixer Fabricated Using a Planar Silicon/Glass Technology
Authors: Krog Jens Peter , Branebjerg Jens , Nielsen Claus Rye , Gravesen Peter
Published: July 2023

One of the major challenges in utilizing the recent advances in micro-fabrication technology for improvements in flow-based chemical analysis systems is to find efficient and reliable ways to mix fluids in microscopic flow systems. In this paper, we report on a mixer unit which ensures fast (milliseconds) mixing in such systems. Our silicon/glass fabrication technology is very suitable for integration of many different flow components in the same system, and furthermore, the transparent glass plate gives unique possibilities for detailed experimental characterization of the mixer performance. This paper also focuses on numerical simulations of flow and diffusion in the mixer which have proven to be very useful tools for the design and optimization of the mixer.
A Bond Graph Model for the Sample Extraction / Injection System of a Micro-Sized Gas Chromatographic Instrument
Authors: Lin Jie , Wang Wanjun , Murphy Michael C. , Overton Edward
Published: July 2023

A bond graph model of the sample extraction/injection system of a prototype portable gas chromatographic instrument has been developed. In addition to performing the same functions as current portable GCs, the new generation of GC instruments is designed to perform extraction of analytes from liquid and solid samples. A novel sample extraction/injection module is essential to the improved performance of the portable instrument, which will include microfabricated components such as inlets, interface chips, fluid channels, control valves, optimal heater/sensor combinations, and multi-port connectors. Predicting the performance of the system in this operating regime requires the modeling and analysis of system behavior in two interacting energy domains, fluid and thermal. Simulation results using the bond graph model closely match available experimental data, with differences typically less than 10%. This demonstrates that fluid dynamic theory for macro-scale systems, and the bond graph method based on it, can be readily applied to micro-scale systems with these dimensions.
Quasi-LIGA Technology for Micromachined Gyroscopes
Authors: Niu Mengnian , Wang Shubo , Wang Xiaodong , Xie Jianfang , Wang Weiyuan
Published: July 2023

This paper reports the preliminary results on the two-gimbal micromachined gyroscopes. The micro-gyroscope structure was analyzed and designed by finite element method (FEM). Based on the designed dimension (gimbal dimension 0.8 × 0.9 mm2 and thickness 3.9 μm), both the intrinsic frequencies of inner and outer gimbals are equal to 2.51 kHz, far from the next resonant mode. The devices were fabricated using quasi-LIGA technology. The electroplated Cu as sacrificial layer and Ni as structural material were used. The whole process was carried out at temperature below 80 °C.
The Application of Micro Field Theory to MEMS Actuators
Authors: Cui T. H. , Zhou Z. Y.
Published: July 2023

This paper presents a new basic concept which is the theory of micro field effect to analyze the actuation mechanism of MEMS (Micro Electro Mechanical Systems) actuators. First, the basic concept and fundamental principle of micro field have been put forward. Then, the micro field effect has been used to analyze the intrinsic quality of two kinds of microactuators, which include an electrohydrodynamic (EHD) micropump and a piezoelectric micromotor as typical examples. Finally, a new kind of piezoelectric micromotor model has been fabricated to carry out experiments. The basic principle of micro field effect has been tested and verified.
Effects of the focus ring on the ion kinetics at the wafer edge in capacitively coupled plasma reactors
Authors: Ma Fang-Fang , Zhang Quan-Zhi , Han Dao-Man , Xiong Zi-Lan , Gao Ming , Wang You-Nian
Published: July 2023

The fabrication process of modern microelectronic devices faces a significant challenge regarding the uniformity of wafer processing during plasma etching. Particularly, nonuniformity is prominent at the wafer edge due to varying electrical properties, leading to sheath bending and distorted ion trajectories. To address this issue, a wafer terminating structure known as a focus ring is employed to modify the sheath structure near the edge of the wafer and ensure uniform ion fluxes. However, the focus ring is subject to erosion caused by the plasma, making it crucial to minimize the ion energy bombarding the focus ring. In light of this, this paper investigates the impact of parameters such as the wafer-focus ring gap, focus ring height, and dielectric constant of the focus ring on the ion angle onto the wafer and the ion energy onto the focus ring. To conduct the analysis, a 2D3V particle-in-cell/Monte Carlo collision model is utilized. The study reveals the existence of horizontal electric fields with opposite directions at the wafer edge and the inner edge of the focus ring. Optimizing the ion angle onto the wafer edge can be achieved by adjusting the material and geometry of the focus ring. Furthermore, reducing the ion energy at the focus ring can be accomplished by increasing the height or decreasing the dielectric constant of the focus ring.
Characterizing the composition, structure, and mechanical properties of magnetron sputtering physical vapor deposition TiN and TiSiN coatings
Authors: Zorn Gilad , Salisbury Joshua , Her Jae-Hyuk , Rose Rachel , Shower Patrick
Published: July 2023

Ti(Si)N coatings were deposited on Si wafers via magnetron sputtering physical vapor deposition technique. Scanning electron microscopy and atomic force microscopy were used to study the morphologies, grain size, and thicknesses of the different films. X-ray diffraction confirmed the formation of the titanium nitride cubic phase. X-ray photoelectron spectroscopy (XPS) was used to study the silicon and oxygen levels in the films, and high resolution XPS was used to determine the surface oxide to nitride ratios as well as the silicon–nitrogen environment. The hardness of these films was then determined with nanoindentation. It was shown that grain size and film density could be controlled by the Si level and the ion bombardment to eliminate the oxygen level in the nitride coatings, which led to the harder films. It was suggested that due to the miscibility of Si, a ternary TiSiN solid solution was formed. Stronger (200) orientation of the TiN B1-NaCl crystals was associated with increased hardness of the coatings. This crystalline structure was preserved after incorporating Si.
In Other Journals
Authors: Seale Maddy , Kelly Priscilla N. , Grocholski Brent , Osborne Ian S. , Smith H. Jesse , Ash Caroline , Simonti Corinne
Published: July 2023

Editors’ selections from the current scientific literature
Tensile cracks can shatter classical speed limits
Authors: Wang Meng , Shi Songlin , Fineberg Jay
Published: July 2023

Brittle materials fail by means of rapid cracks. Classical fracture mechanics describes the motion of tensile cracks that dissipate released elastic energy within a point-like zone at their tips. Within this framework, a “classical” tensile crack cannot exceed the Rayleigh wave speed,

c
R

. Using brittle neo-hookean materials, we experimentally demonstrate the existence of “supershear” tensile cracks that exceed shear wave speeds,

c
R

. Supershear cracks smoothly accelerate beyond

c
R

, to speeds that could approach dilatation wave speeds. Supershear dynamics are governed by different principles than those guiding “classical” cracks; this fracture mode is excited at critical (material dependent) applied strains. This nonclassical mode of tensile fracture represents a fundamental shift in our understanding of the fracture process.
Origin of diamond-bearing eruptions revealed
Authors: Voosen Paul
Published: July 2023

Deep mantle waves from continental rifting trigger mysterious kimberlite volcanoes
Studies find little impact of social media on polarization
Authors: Kupferschmidt Kai
Published: July 2023

But some are uneasy about Meta’s role in unprecedented research collaboration
Awareness and related factors of depressive symptoms in breastfeeding people in South Korea: a survey-based cross-sectional study
Authors: Song Jiyoung , Lee Eunwon
Published: July 2023

Objectives

This study identifies depressive symptoms and the factors that could explain its presence in breastfeeding people.

Design

This study is a cross-sectional study from national survey data.

Setting and participants

Data were derived from the 2019 Korean Community Health Survey. The study subjects were breastfeeding people under the age of 50.

Primary outcome measures

Depressive symptoms in breastfeeding people were classified according to the Patient Health Questionnaire-9 (PHQ-9) score. Physical and health behaviours were considered as factors related to depressive symptoms. A multilevel logistic regression analysis was used.

Results

Among 497 participants, 19.4% (n=97) of breastfeeding people were depressed. We found that depressive symptoms were associated with age (31–35, OR: 0.79, 95% CI: 0.67 to 0.94; 35–49, OR: 0.42, 95% CI: 0.32 to 0.56), rural setting (OR: 0.62, 95% CI: 0.51 to 0.76), economic activity (OR: 0.75, 95% CI: 0.61 to 0.91) and physical health (diabetus mellitus or hypertension, OR: 5.17, 95% CI: 3.78 to 7.06).

Conclusions

This study implies that socioeconomic factors, physical health and health behaviours may influence depressive symptoms in breastfeeding people. These findings should be used as descriptive data to support the development of education programmes to help breastfeeding people.