Unraveling the comonomer distribution in ethylene - vinyl ester terpolymers through liquid chromatography with infrared detection.

Polyolefins are the most commercially relevant polymers by volume. A readily available feedstock and their tailor-made microstructure allow to adapt polyolefins to many fields of application. Important molecular design features of olefin copolymers are the molar mass distribution (MMD) with the corresponding average values, comonomer type, chemical composition distribution (CCD) with the corresponding average and the tacticity distribution (TD). Advanced separation techniques i.e., high-temperature gel permeation chromatography (HT-GPC) as well as its hyphenation with high-temperature high performance liquid chromatography (HT-HPLC) in the form of high-temperature two-dimensional liquid chromatography (HT 2D-LC) have been successfully applied in this work. This allowed to deeply analyze the molecular heterogeneities of complex polyolefin terpolymers consisting of ethylene, vinyl acetate and branched vinyl ester monomers. By using filter-based infrared detection, the capabilities of HT-GPC are further extended so that the distribution of methyl- and carbonyl groups could be obtained along the molar mass axis. Using porous graphitic carbon (PGC) as a stationary phase for HT-HPLC separation provided information about the CCD of these complex polyolefins from experimental data as part of the hyphenated approach of HT 2D-LC. The latter revealed the full MMD x CCD distribution function, which is the key for a comprehensive analysis of the bivariate molecular structure of the polyolefin terpolymers.

Density functional theory computation of the intermolecular interactions of Al2@C24 and Al2@Mg12O12 semiconducting quantum dots conjugated with the glycine tripeptide.

The nature of intermolecular forces within semiconductor quantum dot systems can determine various physicochemical properties, as well as their functions, in nanomedical applications. The purpose of this study has been to investigate the nature of the intermolecular forces operating between Al2@C24 and Al2@Mg12O12 semiconducting quantum dots and the glycine tripeptide (GlyGlyGly), and also consider whether permanent electric dipole-dipole interactions play a significant role vis-à-vis these molecular systems. The energy computations, including the Keesom and the total electronic interactions and the energy decomposition, together with the quantum topology analyses were performed. Our results demonstrate that no significant correlation is found between the magnitude and orientation of the electrical dipole moments, and the interaction energy of the Al2@C24 and Al2@Mg12O12 with GlyGlyGly tripeptide. The Pearson correlation coefficient test revealed a very weak correlation between the quantum and the Keesom interaction energies. Apart from the quantum topology analyses, the energy decomposition consideration confirmed that the dominant share of the interaction energies was associated with the electrostatic interactions, yet both the steric and the quantum effects also made appreciable contributions. We conclude that, beside the electrical dipole-dipole interactions, other prominent intermolecular forces, such as the polarization attraction, the hydrogen bond, and the van der Waals interactions can also influence the interaction energy of the system. The findings of this study can be utilized in several areas in the field of nanobiomedicine, including the rational design of cell-penetrating and intracellular drug delivery systems using semiconducting quantum dots functionalized with a peptide.

Computational study and validation of a novel passive hand tremor attenuator.

Tremors are a prevalent movement disorder due to a nervous system condition that leads to involuntary muscle movements observed in patients. This paper converts the tremorous anatomical human arm model to a single degree of freedom (SDOF) forced vibration problem. The mathematical modelling with Euler-Lagrange's equation is performed for the SDOF human arm model with two different potential vibration absorbers. A computational study is conducted on MATLAB Simulink by MathWorks Inc. (Natick, MA) to compare two absorbers, and the results are verified on the multibody dynamics simulation solution software, MSC Adams by Hexagon AB. It is concluded that the T beam-shaped vibration absorber represented a higher amplitude reduction, up to 80%, compared to the inertial mass absorber, which had an amplitude reduction of 65% over the range of frequencies. Experiments conducted with the T beam absorber prototype also support the computational findings. Future research focuses on designing an ergonomic wearable device with a proposed T-beam absorber that can passively attenuate the tremor at various frequencies.

Valve interstitial cells under impact load, a mechanobiology study.

Understanding the relationship between mechanobiology and the biosynthetic activities of the valve interstitial cells (VICs) in health and disease under severe dynamic loading conditions is of particular interest. The purpose of this study is to further understand the mechanobiology of heart valve leaflet tissue and the VICs under impact forces. Two novel computational and experimental platforms were developed to study the effect of impact load on the VICs to monitor for apoptosis. The first objective was to design and develop an apparatus to experimentally study viability (apoptosis) of the porcine heart valve leaflet tissue VICs in the aortic position under controlled impact forces. Apoptosis was assessed based on terminal transferase dUTP nick end-labelling (TUNEL) assay. The second objective was to develop a computational platform to estimate the stress and strain fields in the vicinity of VICs when the tissue experiences impact forces. A nonlinear finite element (FE) model with an anisotropic, hyperelastic and heterogeneous material model for the matrix and cells was developed. Preliminary results confirm that interstitial cells are successfully resistant to impact loads up to 30 times more than normal physiological conditions. Additionally, the structure and composition of heart valve leaflet tissue provides a mechanical shield for VICs protecting them from excessive mechanical forces such as impact loads. Although, the entire tissue may experience excessive stresses, which may lead to structural damage, the stresses around and near VICs remain consistency low. Results of this study may be used for heart valve leaflet tissue-engineering, as well as further understanding the mechanobiology of the VICs in health and disease.

A review of the experimental methods and results of testing the mechanical properties of Tunica Albuginea.

The present work provides a comprehensive review of the literature on the mechanical properties and existing human tunica albuginea tissue testing methods. Assessments were completed on papers reporting experimental values of Young's modulus, tensile strength, puncture strength, stiffness, toughness, and strain at the ultimate tensile strength (UTS). A high degree of variability in the reported experimental values was found; Young's modulus ranged from 5 MPa to 118 MPa, and tensile strength went from 1.1 MPa to 6.1 MPa. A comparison of the variability of the reported experimental values for puncture strength, stiffness, toughness, and strain at the UTS could not be completed due to a lack of experimental results. This review discusses the pathophysiology and surgical treatment of erectile dysfunction and Peyronie's disease, variability in the existing reported mechanical properties, the impact of the variability of mechanical properties on in silico models and explores the absence of a standardised testing method as a possible reason for the variable in results. Finally, this work attempts to provide suggestions for standardising future mechanical testing of the tunica albuginea through minimising and reporting freeze/thaw cycling, noting the proximal/distal region of the cadaver tunica sample, reporting the orientation (o'clock position) of the cadaver tunica sample, and testing the cadaver tunica samples in bi-axial tension. Ultimately, standardising the testing methodologies of the tunica albuginea will provide higher confidence in reported mechanical property values.

Home Health Care Problem with Synchronization Visits and Considering Samples Transferring Time: A Case Study in Tehran, Iran.

Health care facilities have not increased in response to the growing population. Therefore, government and health agencies are constantly seeking cost-effective alternatives so they can provide effective health care to their constituents. Around the world, health care organizations provide home health care (HHC) services to patients, especially the elderly, as an efficient alternative to hospital care. In addition, recent pandemics have demonstrated the importance of home health care as a means of preventing infection. This study is the first to simultaneously take into account nurses' working preferences and skill levels. Since transferring samples from the patient's home to the laboratory may affect the test results, this study takes into account the time it takes to transfer samples. In order to solve large instances, two metaheuristic algorithms are proposed: Genetic Algorithms and Particle Swarm Optimization. Nurses are assigned tasks according to their time windows and the tasks' time windows in a three-stage scheduling procedure. Using a case study set in Tehran, Iran, the proposed model is demonstrated. Even in emergencies, models can generate effective strategies. There are significant implications for health service management and health policymakers in countries where home health care services are receiving more attention. Furthermore, they contribute to the growing body of knowledge regarding health system strategies by providing new theoretical and practical insights.

All optical divergence and gradient operators using surface plasmon polaritons.

In this paper, we propose a plasmonic structure based on Kretschmann configuration capable of performing various computational tasks, i.e. two dimensional isotropic differentiation, gradient and divergence computation. By means of two polarizers, a non-trivial topological charge can be generated in the transfer function of the structure thereby implementing a two dimensional differentiator. By using only one polarizer, on the other hand, the structure is able to compute either the gradient of the field distribution of a polarized light beam or the divergence of the field of an unpolarized light beam. The performance of the proposed structure in two dimensional differentiation has been assessed and compared with its other counterparts by a figure of merit introduced in [Opt. Express28, 898 (2020)10.1364/OE.379492]. The result proves the dominance of our two-dimensional differentiator over similar works in the literature.

Design and fabrication of a novel passive hand tremor attenuator.

Parkinson's disease is most highly recognised by tremors of the hands that occur in those afflicted with the disease. Though the symptoms of Parkinson's disease involving motor function begin with very slight tremors of the hands, they further develop into issues such as difficulty swallowing, severe postural problems and extremely limited mobility. In this study, a method of reducing these tremors that appear during the early stages of the disease is developed by creating a wearable passive device that reduces vibrations of the hand and arm through the use of magnetic actuators. The proposed wearable technology has surpassed other known alternatives in selected testing scenarios while possessing a light weight of only 120 grams.

Mechanics of foot orthotics: material properties.

Orthotics have been utilised by clinicians for many years to treat foot-related abnormalities. With advancements in material sciences, the footwear industry started utilising synthetic materials which have better and suitable properties. Clinicians, who prescribe foot insoles, need to have an extensive understanding of the properties and characteristics of insole materials, to make informed decisions to meet the patients' needs. This thesis showcases utilised techniques and systems to evaluate orthosis properties as well as current criteria to date. Researchers have utilised a variety of testing techniques to examine properties of insole materials including; bench testing, simulated in-shoe conditions, in-shoe testing, and finite element analysis. Even though, there is a great understanding of material properties with endless diverse composition and thicknesses of each material makes clinical recommendations on the choice of material an impossible task. As the footwear orthosis industry shifts the focus from material to design, some researchers explore various anisotropic materials to create a homogeneous insole that can support as well as relieve pressure on patient's feet.

Interaction analysis of a pregnant female uterus and fetus in a vehicle passing a speed bump.

Pregnant vehicle occupants experience relatively large acceleration when the vehicle passes a speed-bump. In this paper, the effect of such sudden acceleration on a pregnant uterus is investigated. A biomechanical model representing the fundamental dynamic behaviors of a pregnant uterus has been developed. The model relates to the 32nd week of gestation when the fetus is in head-down, occipito-anterior position. Considering the drag and squeeze effects of the amniotic fluid, we derive a comprehensive differential equation that represents the interaction of the uterus and fetus. Solving the governing equation, we obtain the system response to different speed-bump excitations. Using the fetal head injury criterion (HIC = 390), we evaluate the model response. Three risk zones (Low, Medium, and High) are introduced, and the effects of excitation characteristics on HIC are investigated. HIC enhances, sub-exponentially, as the excitation amplitude (width) increases (decreases). Three risk-bounds, corresponding to 25%, 75%, and 100% risk of injury, are developed in the "width-amplitude" and the "frequency-amplitude" planes. Considering a typical speed-bump of width and excitation amplitude of 0.5 m and 0.12 m, respectively, the driver should not hit the speed-bump at 42 km/h or more. We advise hitting such speed-bumps under 25 km/h, based on this paper's findings. According to the risk-bounds, the injury risk of an arbitrary speed-bump excitation, at any desired vehicle speed, can be determined. The findings can help to understand how a pregnant uterus and fetus are subjected to risk caused by a vehicle passing a speed-bump and to expand our knowledge to improve safety during pregnancy.

The Apex bileaflet mechanical heart valve.

Mechanical Heart Valves (MHVs) are known for their excellent lifespan and feasibly are the most reliable and stable valves amongst all prosthetic valves. Successful bileaflet MHVs such as the St. Jude Medical (SJM) are known for providing central blood flow and minimal pressure drop across the valve. However, due to their non-physiological flow conditions, they still suffer from hemodynamic complications, that is, red blood cell (RBC) lysis and/or thrombogenicity, to date. Our hypothesis is that the design of MHVs can be improved so that their hemodynamics can be comparable to those of tissue valves. In this study, a new concept for the design of MHVs is proposed. To accomplish this, we identified the major design limitations of bileaflet MHVs, such as the gold standard SJM valve as well as the believed contributing factors to their thrombogenicity. We developed a novel design architecture for bileaflet MHVs that addressed these limitations, and from it, the Apex Valve (AV). Our experimental assessment of the AV found that its hemodynamics were closer to that of a bioprosthetic valve than of a bileaflet MHV. This design has been filed as a US Provisional Patent.

Exodex Adam-A Reconfigurable Dexterous Haptic User Interface for the Whole Hand.

Applications for dexterous robot teleoperation and immersive virtual reality are growing. Haptic user input devices need to allow the user to intuitively command and seamlessly "feel" the environment they work in, whether virtual or a remote site through an avatar. We introduce the DLR Exodex Adam, a reconfigurable, dexterous, whole-hand haptic input device. The device comprises multiple modular, three degrees of freedom (3-DOF) robotic fingers, whose placement on the device can be adjusted to optimize manipulability for different user hand sizes. Additionally, the device is mounted on a 7-DOF robot arm to increase the user's workspace. Exodex Adam uses a front-facing interface, with robotic fingers coupled to two of the user's fingertips, the thumb, and two points on the palm. Including the palm, as opposed to only the fingertips as is common in existing devices, enables accurate tracking of the whole hand without additional sensors such as a data glove or motion capture. By providing "whole-hand" interaction with omnidirectional force-feedback at the attachment points, we enable the user to experience the environment with the complete hand instead of only the fingertips, thus realizing deeper immersion. Interaction using Exodex Adam can range from palpation of objects and surfaces to manipulation using both power and precision grasps, all while receiving haptic feedback. This article details the concept and design of the Exodex Adam, as well as use cases where it is deployed with different command modalities. These include mixed-media interaction in a virtual environment, gesture-based telemanipulation, and robotic hand-arm teleoperation using adaptive model-mediated teleoperation. Finally, we share the insights gained during our development process and use case deployments.

Wrinkle-induced tear in the mitral valve leaflet tissue: a computational model.

In this study, we offer a numerical platform to detect the locations of high-stress zones in the prosthetic heart valve, in the mitral position, during the closing phase due to existing wrinkles. The intended prosthetic valves in this study have the same shape as the native mitral valve but made of synthetic biomaterials. We assume the most high-risk locations for ruptures to either initiate or propagate are at the base of existing wrinkles. We developed a finite element model for the human mitral valve. A mesh model was effectively created to account for the uneven stress distribution and high-stress concentration zones in the valve tissue structure. The constitutive material model used in this study is anisotropic and hyperelastic such that the membrane elements are used for the leaflets and spar elements are utilised for the mitral valve cords for which it was assumed flexural stiffness is insignificant for both sets of elements. We developed a novel and effective computational model for the simulation of wrinkles in the valve leaflet during the closing phase. The proposed numerical model provided a quick but precise assessment for the detection of locations of rips and tears on the leaflet tissue during the closing phase. The proposed model is an essential step for the design of material and geometry of leaflets of prosthetic heart valves made of polymers or tissue materials in the mitral position.

New synthetic mitral valve model for human prolapsed mitral valve reconstructive surgery for training.

The training process of young surgeons is highly desirable in order for them to gain an understanding of the quality of care and patient safety required during cardiac surgeries, however, it may take a few years of practice in order for them to properly develop these skills. Artificial life-like platforms and models are extremely recommended for teaching hands-on and real-world practice in both junior and even experienced medical professionals and surgeons. Suitable and accessible training tools are of significant importance for simulating a particular surgery in order to provide practice opportunities for a specific surgical procedure. In this study, we focussed on the simulation of the human mitral valve prolapse reconstructive surgery. An innovative, artificial, biomimetic model was designed and fabricated made of Cryogel biomaterial developed in our lab that is suitable for the precise practice on the mitral valve prolapse model. The proposed model is mainly made up of polyvinyl alcohol (PVA) cryogel, which is designed to resemble the geometric and mechanical properties of a diseased (prolapse) mitral valve. We simulated the constructive prolapsed mitral valve surgery entirely on a synthetic platform. The platform was made available to four certified cardiac surgeon and there were unanimously very positive with no considerable differences in the procedural assessments between them. The proposed model has a similar appearance and texture to that of a diseased mitral valve and holds consistent mechanical properties to those of the real tissue. The offered technology may be used for other cardiothoracic reconstructive surgeries with high precision and consistency.

Transcatheter Mitral Valve Replacement: State of the Art.

The emergence of transcatheter aortic valve replacement (TAVR) has segued the development of transcatheter mitral valve (MV) repair devices. Transcatheter mitral valve repair has become a well-established alternative for patients with severe primary and secondary mitral regurgitation (MR) and with a perceived surgical risk. Transcatheter mitral valve replacement (TMVR) could become a more complete form of reduction of severe MR compared to MV repair devices, albeit with significant engineering challenges and all the risks associated with a bioprosthetic heart valve. The development of TMVR devices has become prominent while companies race to become the first commercially available system. Careful consideration of design challenges should be conducted by the developmental companies to ensure successful devices. Preclinical and clinical trials have shown promising results, showcasing the feasibility of total valve replacement utilizing transcatheter procedure techniques. Further development, testing, and trials need to be conducted before TMVR can become a sensible MR treatment. This review describes design challenges and considerations along with the state of the art, involving designs in both clinical and preclinical stages.

Soft robotic in the construction of prosthetic heart valve: a novel approach.

In this study, we describe the design, fabrication and computational testing of a new prosthetic device for aortic valve replacement. The device is an active stent composed of a silicone rubber during initial prototyping, with adaptation towards a hydrogel, poly-vinyl alcohol reinforced with bacterial cellulose nanofibres underway. The nature of the stent is soft robotic (SR), where an increase in internal pressure of the pneumatic network causes an increase in the internal diameter of the device. When working in tandem with the SR heart valve, described briefly, pulsations of the blood and the energy gained from ventricular pressure actuates the valve-and-stent combination. This increases the effective orifice area of the entire device and addresses an issue with small sized heart valves facing prosthesis-patient mismatch.

CBTH: A New Algorithm for Maximum Rooted Triplets Consistency Problem.

BACKGROUND: Phylogenetics is a branch of bioinformatics that studies and models the evolutionary relationships between currently living species. A phylogenetic tree is the simplest possible model in which leaves are distinctly labeled by species. Rooted triplets are one of the most important inputs for constructing rooted phylogenetic trees. A rooted triplet is the simplest possible rooted tree that contains information and explains the biological relation between three species. OBJECTIVES: The problem of constructing a rooted phylogenetic tree that contains the maximum number of input triplets is a maximization problem and is known as the maximum rooted triplets consistency (MRTC) problem. MRTC problem is an NP-hard problem, so there is no any polynomial exact solution for it. The goal is to introduce a new efficient method to solve MRTC. MATERIALS AND METHODS: In this research, a new algorithm called CBTH, is introduced innovatively for MRTC problem with the goal to improve the consistency of input rooted triplets with the final rooted phylogenetic tree. RESULTS: In order to show the efficiency of CBTH, the CBTH is compared with TRH on biological data. According to our knowledge, TRH is one of the best methods for MRTC problem on rooted triplets that are obtained from biological data. The Experimental results show that CBTH outperforms TRH based on rooted triplet consistency parameter in the same time order. CONCLUSION: The introduced method (CBTH) solve MRTC problem with high performance without increasing time complexity compared to the other state of the art algorithms.

Rigid-bar loading on pregnant uterus and development of pregnant abdominal response corridor based on finite element biomechanical model.

During pregnancy, traumas can threaten maternal and fetal health. Various trauma effects on a pregnant uterus are little investigated. In the present study, a finite element model of a uterus along with a fetus, placenta, amniotic fluid, and two most effective ligament sets is developed. This model allows numerical evaluation of various loading on a pregnant uterus. The model geometry is developed based on CT-scan data and validated using anthropometric data. Applying Ogden hyper-elastic theory, material properties of uterine wall and placenta are developed. After simulating the "rigid-bar" abdominal loading, the impact force and abdominal penetration are investigated. Findings are compared with the experimental abdominal response corridor, previously developed for a nonpregnant abdomen. "Response corridor" denotes a bounded envelope in response space, within which the system responses usually lie. Results show that at low abdominal penetrations (less than 45 mm), the pregnant abdomen response is highly compatible with the nonpregnant case. While, at large penetrations, the pregnant abdomen demonstrates stiffer behavior. The reason must be the existence of a fetus in the model. This reveals that the existing response corridors would not be reliable to be extended for a pregnant abdomen. Hence, response corridor development for a pregnant abdomen is a crucial task. In this study, a new fixed-back rigid-bar loading response corridor is proposed for a pregnant abdomen using the load-penetration behavior of the developed model. This model and response corridor can help to study the pregnant uterus response to environmental loading and investigate the injury risk to the uterus and fetus.

Mechanics of Atherosclerotic Plaques: Effect of Heart Rate.

PURPOSE: Atherosclerotic plaques are highly heterogeneous, nonlinear materials with uncharacteristic structural behaviors. It is well known that mechanics of atherosclerotic plaques significantly depend on plaque geometry, location, composition, and loading conditions. There is no question that atherosclerotic plaques are viscoelastic. Plaques are characterized as the buildup of low-density lipoprotein cholesterol, macrophages, monocytes, and foam cells at a place of inflammation inside arterial walls. Lipid core and fibrous cap are the two major ingredients that are frequently used for the identification of main constituting quantities of atherosclerotic plaques. The lipid core contains of debris from dead cells, esterified cholesterol and cholesterol crystals. The fibrous cap contains smooth muscle cells and collagen fibers. All these materials contribute to the viscoelastic properties of atherosclerotic plaques. Computational studies have shown great potential to characterize this mechanical behavior. Different types of plaque morphologies and mechanical properties have been used in a computational platform to estimate the stability of rupture-prone plaques and detect their locations. In this study for the first time to the best of authors' knowledge, we hypothesize that heart rate is also one of the major factors that should be taken into account while mechanics of plaques is studied. METHOD: We propose a tunable viscoelastic constitutive material model for the fibrous cap tissue in order to calculate the peak cap stress in normal physiological (dynamic) conditions while heart rate changes from 60 bpm to 150 bpm in 2D plane stress models. A critical discussion on stress distribution in the fibrous cap area is made with respect to heart rate for the first time. RESULTS: Results strongly suggest the viscoelastic properties of the fibrous cap tissue and heart rate together play a major role in the estimation of the pick cap stress values. CONCLUSIONS: The results of current study may provide a better understanding on the mechanics of vulnerable atherosclerotic plaques and that any experimental methods assessing the viscoelasticity of plaque composition during progression are highly desirable.