Application Of External Force Research Articles

Effects of scCO2 foaming process and post‐vulcanization method on cellular structure, mechanical properties, and thermal stability of PMVQ foams

AbstractIn this paper, the microcellular foam materials of methyl vinyl phenyl silicone rubber (PVMQ) were prepared by supercritical foaming technology (SFT) and high temperature compression molding. The effect of supercritical carbon dioxide (scCO2) on the vulcanizing properties of PVMQ composite was investigated because vulcanization of microcellular PVMQ foams played an important role on the cellular structure and mechanical properties. It was found that the sulfurization reaction of PVMQ composite was inhibited by scCO2, which led to reduction of apparent activation energy (Ea) of PVMQ composite. Compared with the existing post‐vulcanization process, the introduction of the high temperature molding can effectively improve the degree of vulcanization of microcellular PVMQ foams, which can solve the problem that the cellular structure will be destroyed during the application of external force. What's more, the mechanical properties of microcellular PVMQ foam were obviously improved. The maximum value of tensile strength and the compressive strength of microcellular PVMQ foam with the high temperature molding respectively increase by 34.7% and 133.3% compared with that of microcellular PVMQ foams with existing post‐vulcanization.

Functional Instability of the Second to Fifth Metacarpophalangeal Joints.

Clinically, functional instability (FI) of metacarpophalangeal joints (MCPJ) is not considered to represent a pathology. This excessive mobility can be detected by the application of external forces to a MCPJ at different angles. Our study aimed to measure the FI of 2nd to 5th MCPJ. A group of 36 healthy right-handed individuals were enrolled. The value of FI was measured in millimeters and verified by a CT scan. Statistical calculations was made in Statistica v.10.0. The largest values of the right and left-hand finger posterior displacement (FI) in the second to fifth MCPJ were obtained in the neutral position 0° (p<0.05). Measurements of volar displacement of the proximal phalanx second to fifth MCPJs in both hands revealed higher values at position 0° (p<0.05). 1. FI of the second to fifth MCPJs is determined by anatomical configuration and dynamic stabilizers. 2. Instability measurements show that posterior displacement of the proximal phalanges is greater by at least 1 mm in the 0° neutral position.

Evaluation of the mechanical behaviour of confectionery with porous structure under the application of external forces

Evaluation of the mechanical behaviour of confectionery with porous structure under the application of external forces

LINC complex independent perinuclear actin organization and cell migration

The link of the metazoan nucleus to the actin cytoskeleton is highly important for actin polymerization and migration of multiple cell types as well as for mechanotransduction and even affects the cellular transcriptome. Several mechanisms of organization of actin filaments next to the nuclear envelope have been identified. Among these mechanisms the most studied one is the Linker of nucleoskeleton and cytoskeleton (LINC) complex-dependent perinuclear actin organization. However, recently additional mechanisms have been identified: an Actin-related protein-2/3 (Arp2/3)-dependent perinuclear actin polymerization during migration of dendritic cells and a perinuclear actin rim that is formed in response to external force application or migration cues. In parallel, there are also reports on cancer cells that migrate in a LINC complex independent manner and on cancers with reduced expression of the LINC complex components. Thus, suggesting that LINC complex independent migration may be associated with tumour formation.

НЕСУЧА ЗДАТНІСТЬ ПОШКОДЖЕНИХ ЗАЛІЗОБЕТОННИХ ДВОТАВРОВИХ КОЛОН

Abstract. The article presents the results of experimental and theoretical studies of the work, the parameters of the stress-strain state and the methodology for calculating the residual bearing capacity of reinforced concrete I-section columns damaged during operation and combat operations. The analysis of the literature on this subject made it possible to study the main factors affecting the residual bearing capacity, namely: the depth of damage; the angle of inclination of the damage front; relative eccentricity of application of external compressive force. A three-factor three-level experimental design has been developed. The conducted field tests of prototypes of damaged reinforced concrete columns made it possible to determine the parameters of the stress-strain state of damaged elements and their actual residual bearing capacity. On the basis of the performed experimental-statistical modeling, the main factors influencing the residual bearing capacity of damaged elements have been established. The prerequisites for calculating damaged reinforced concrete I-beams are proposed and equilibrium equations are drawn up. The proposals set out in the article are based on the main provisions of the current norms and expand the effect of their use. The analysis of influence of various factors on bearing capacity of the damaged I-beam reinforced concrete columns is carried out. It was found that the columns can withstand a maximum destructive load of 1738 kN at an angle of inclination of the damage front of 60о and in the absence of relative eccentricity. And the least destructive load columns can withstand in the absence of the angle of the damage front, and the relative eccentricity will be 1/8 of the applied load. On the basis of the conducted researches the technique of definition of reliably substantiated residual bearing capacity of reinforced concrete compressed elements of a T-profile profile damaged in the course of operation is developed. This makes it possible to determine the possibility of further trouble-free operation of structures or the need for their reinforcement or reconstruction.

Wetting properties of dehydrated biofilms under different growth conditions

Biofilms are resilient to environmental conditions and often resistant even to strong disinfectants. It is crucial to investigate their interfacial properties, which can be effectively characterized by wetting analysis. Wetting phenomena on biofilm surfaces have been poorly investigated in literature, in particular a systematic study of wetting on real biofilm-coated substrates including the application of external body forces (forced wetting, i.e.: centrifugal and gravitational forces) is missing. The aim of this work is to study the role of nutrient and shear flow conditions on wetting properties of Pseudomonas fluorescens dehydrated biofilms, grown on glass substrates. An innovative device (Kerberos®), capable to study spreading/sliding behavior under the application of external body forces, is used here for a systematic analysis of wetting/de-wetting liquid droplets on horizontal substrates under the action of tangential forces. Results prove that, under different growth conditions, (i.e., nutrients and imposed flow), biofilms exhibit different wetting properties. At lower nutrient/shear flow conditions, biofilms show spreading/sliding behavior close to that of pure glass. At higher nutrient and shear flow conditions, droplets on biofilms show spreading followed by imbibition soon after deposition, which leads to peculiar droplet depinning during the rotation test. Wetting properties are derived as a function of the rotation speed from both top and side views videoframes through a dedicated image analysis technique. A detailed analysis of biofilm formation and morphology/topography is also provided here.

Quantifying force transmission through fibroblasts: changes of traction forces under external shearing

Mammalian cells have evolved complex mechanical connections to their microenvironment, including focal adhesion clusters that physically connect the cytoskeleton and the extracellular matrix. This mechanical link is also part of the cellular machinery to transduce, sense and respond to external forces. Although methods to measure cell attachment and cellular traction forces are well established, these are not capable of quantifying force transmission through the cell body to adhesion sites. We here present a novel approach to quantify intracellular force transmission by combining microneedle shearing at the apical cell surface with traction force microscopy at the basal cell surface. The change of traction forces exerted by fibroblasts to underlying polyacrylamide substrates as a response to a known shear force exerted with a calibrated microneedle reveals that cells redistribute forces dynamically under external shearing and during sequential rupture of their adhesion sites. Our quantitative results demonstrate a transition from dipolar to monopolar traction patterns, an inhomogeneous distribution of the external shear force to the adhesion sites as well as dynamical changes in force loading prior to and after the rupture of single adhesion sites. Our strategy of combining traction force microscopy with external force application opens new perspectives for future studies of force transmission and mechanotransduction in cells.

FEM Based Elasto-Electric Analysis of Elastomers for Pharmaceutical Applications

Elastomer materials are very important due to weak intermolecular forces and very low Young's modulus and have high failure strain. Due to these properties, they are used in a large number of applications especially in pharmaceutical industry and medical / surgical equipment etc. Electrostatic discharge on such material is a potential hazard for the operator who is dealing with elastomers. In the research presented here, a detailed analysis on the elasto-electric analysis of 03x elastomers is analyzed in detail by using Finite Element Method (FEM). A CAD model is generated in accordance with an early research on elasto-electric study of Silicon material. Subsequently FEM based analysis is carried out to study vital electrostatics properties like Surface deformation and surface potential distribution developed on the application of external forces on 03x types of elastomers i.e. Silicon Rubber, Nitrile (NBR) and Poly Vinyl Chloride (PVC). The whole study is carried out in COMSOL multi-physics software. Analysis showed that the electric field developed on the surface of the elastomer is dependent on the deformation on non-linear nature and depends upon the material properties. FEM based results show that Silicon Rubber develops maximum deformation and electric potential of three chosen materials up to 50mm and 3150V respectively. Based on the conducted analysis, Silicon Rubber is widely recommended for its utilization in Pharmaceutical applications requiring electrostatics.

Response of laboratory plasma influenced by a feedback loop to external force

AbstractThis study experimentally examines the sensitivity of laboratory plasma influenced by a feedback loop to applied external force, with the objective of gaining insight into chaos control in plasma. The ionization waves in laboratory plasma are adopted as the medium of a typical nonlinear system. In the case of a system without the influence of feedback (defined as system A), the orbit of the chaotic system changes to a periodic one as the intensity of the applied external force increases. In the case of a system with the influence of feedback (defined as system B), the chaotic orbit changes to a periodic one by the application of external force with lower intensity (approximately two-thirds) compared to system A. This reveals that the feedback loop enhances the response of the system to external forces.

Hericium erinaceus and Coriolus versicolor Modulate Molecular and Biochemical Changes after Traumatic Brain Injury.

Traumatic brain injury (TBI) is a major health and socioeconomic problem affecting the world. This condition results from the application of external physical force to the brain which leads to transient or permanent structural and functional impairments. TBI has been shown to be a risk factor for neurodegeneration which can lead to Parkinson’s disease (PD) for example. In this study, we wanted to explore the development of PD-related pathology in the context of an experimental model of TBI and the potential ability of Coriolus versicolor and Hericium erinaceus to prevent neurodegenerative processes. Traumatic brain injury was induced in mice by controlled cortical impact. Behavioral tests were performed at various times: the animals were sacrificed 30 days after the impact and the brain was processed for Western blot and immunohistochemical analyzes. After the head injury, a significant decrease in the expression of tyrosine hydroxylase and the dopamine transporter in the substantia nigra was observed, as well as significant behavioral alterations that were instead restored following daily oral treatment with Hericium erinaceus and Coriolus versicolor. Furthermore, a strong increase in neuroinflammation and oxidative stress emerged in the vehicle groups. Treatment with Hericium erinaceus and Coriolus versicolor was able to prevent both the neuroinflammatory and oxidative processes typical of PD. This study suggests that PD-related molecular events may be triggered on TBI and that nutritional fungi such as Hericium erinaceus and Coriolus versicolor may be important in redox stress response mechanisms and neuroprotection, preventing the progression of neurodegenerative diseases such as PD.

Co-doping optimized hydrogel-elastomer micro-actuators for versatile biomimetic motions.

Hydrogels can respond to changes in humidity or temperature, while elastomers can resist structural collapse due to dehydration or external force application. A hybrid bilayer of hydrogel-elastomers while retaining the merits of both the hydrogels and elastomers has emerged as a promising stimuli-responsive micro-actuator. However, the preparation of a hydrogel-elastomer micro-actuator requires multiple steps, mainly due to the differences in the surface properties of these two materials. Among them, the steps to surface-treat the elastomer and functionalize the material of each layer involve intricate processes and excessive consumption of resources. In this work, we introduce a co-doping method to optimize the preparation of a stimuli-responsive hydrogel-elastomer micro-actuator. The surface treatment and functionalization processes are combined into one step by directly doping the polymerization initiator and functional nanomaterials into the hybrid bilayer. The thermo-responsive hydrogel is combined with a photothermal elastomer to fabricate a soft micro-actuator that can bend and unbend in response to changes in humidity and light. Based on this actuator, a set of biomimetic soft micro-robots were developed, demonstrating a series of motions, such as grabbing, crawling, and jumping. This strategy of stimuli-responsive micro-actuator preparation can benefit the hydrogel-elastomer hybrid micro-robot designs for applications ranging from self-locomotive robots in environmental monitoring to drug delivery in biomedical engineering.

A study of the cultivator suspension’s strength based on its solid model in Autodesk Inventor Professional

The article is devoted to the study of the stress-strain state cultivator suspension in the Autodesk Inventor Professional program. To solve this problem, a solid-state suspension model has been developed. Four schemes of the application of external forces and restrictions on the suspension parts movement are described, which describe the condition of the cultivator in critical situations - the suspension’s paw clings to an obstacle. The calculations were performed in the “stress analysis” environment. The obtained results made it possible to justify the possibility using two of the four considered schemes to formulate a plan for a comprehensive study of the cultivator’s health when various changes are made to its design. The ultimate goal of design changes is to reduce metal consumption and the use of more affordable materials in the manufacture of the cultivator frame.

Brain Injuries in American Football: Understanding the Injury, Difficulty in Helmet Optimization, and Current Communication Practices – A Narrative Review

Background: Over 2.7 million people suffer traumatic brain injuries (TBIs) annually in the United States. TBI involves the application and generation of external forces and impulse loads respectively to the head whereby the brain moves relative to the skull. Despite numerous studies, further understanding of TBIs is necessary, requiring consistent attention. Objective: The purpose of this article is to investigate the history of American football helmets and provide an academic and practitioner review as it relates to TBIs. This study is a literature review that also considers perspectives from an autoethnographic frame. Method: An extensive literature review was performed to assess the history of TBI as it relates to American football. This article evaluates helmet design optimization and American football safety as well as an exploration into the sports’ education methods for players and staff alike. Results: Despite developing helmet designs that can better attenuate impact forces, reducing linear and rotational movement, the skull and brain move very differently relative to one another. Helmet designs and tools for measuring forces require further validation techniques to determine resultant forces and movement for the brain. Current biomechanics research lacks sufficient methodology for defining TBI thresholds, making helmet optimization difficult. Conclusion: According to past research, no helmet can eliminate all TBI risk; however, processes are in place lead by the National Football League (NFL) and NFL Players Association to educate players, coaches, and staff at all levels of competition of the protective capabilities of available helmet options.

Human Dental Pulp Tissue during Orthodontic Tooth Movement: An Immunofluorescence Study.

The orthodontic tooth movement is the last step of several biological processes that take place after the application of external forces. During this process, dental pulp tissue is subjected to structural and protein expression modifications in order to maintain their integrity and functional morphology. The purpose of the present work was to perform an in vivo study, evaluating protein expression modifications in the human dental pulp of patients that have undergone orthodontic tooth movement due to pre-calibrated light force application for 30 days. Dental pulp samples were extracted from molars and premolars of the control group and after 7 and 30 days of treatment; the samples were then processed for immunofluorescence reactions using antibodies against fibronectin, collagen I and vascular endothelial growth factor (VEGF). Our results show that, after 7 days of treatment, all tested proteins change their pattern expression and will reset after 30 days. These data demonstrate that the dental pulp does not involve any irreversible iatrogenic alterations, supporting the efficacy and safety of using pre-calibrated force application to induce orthodontic tooth movement in clinical practice.

SIMULATION STUDY OF THE DIGITAL TEMPERATURE SENSOR OPERATION IN CASE OF A NON-STANDARD MECHANICAL IMPACT OF THE NPP EQUIPMENT

The article presents the results of an experimental study relevant to the effective organization of temperature control of thermomechanical equipment at nuclear power plants (turbines, pumps, steam generators, deaerators, etc.). Bench studies of the reaction of the DS18B20 digital intelligent temperature sensor, which is supposed to be introduced at Ukrainian nuclear power plants, to the application of external compression force to its body, which may occur under conditions typical for the operation of equipment operating at nuclear power plants, have been carried out. An electrical circuit diagram has been developed for a reset signal simulation device (for bench modeling of a sensor application system). The issues of identifying a sign in the sensor output signal informing about the effect of an external compression force on its body are considered. The technique of bench experiments and processing of research results necessary to address the issue of introducing new digital measuring equipment for temperature control of thermomechanical equipment of nuclear power plants is given.

Влияние особых положений на жесткость механизмов параллельной структуры

Due to a sharp increase in the accuracy of manufacturing and quality control of mechanical engineering products, robots based on mechanisms with closed-loop kinematic chains have become a promising area of engineering. One of the advantages of parallel structure mechanisms over serial mechanisms is their increased rigidity. The absence of patterns in the change of rigidity in the working zone and the influence of the so-called special positions necessitate the development of new methods of optimization synthesis of the mechanism. This paper presents an approach based on the Jacobian matrix using which it is possible to determine rigidity in the worst direction of the external force application in each point of the working zone. The same approach can also be used for determining the shape and size of the effective working zone. An example of a flat five-chain mechanism is used to demonstrate the application of the method and obtain a matrix of chain rigidity, construct the parallelogram of forces and determine rigidity distribution in the working zone. It is shown that when approaching a special position, the rigidity of the mechanism decreases ten-fold, and in the special position it equals a zero. The proposed method can be used for optimizing the geometrical parameters of the mechanism on the conditions of maximising the effective working zone.

Polyethylene wax as an alternative to mineral fillers for preparation of reinforced pressure-sensitive adhesives

Phase behavior, rheology and adhesive properties of polyisobutylene-based blends containing up to 60 wt% of polyethylene wax were studied. Polyisobutylene and wax partially dissolve in each other at high temperatures, which strongly reduce the viscosity of the blends and facilitate their mixing. When cooled, the wax loses its solubility in the polymer matrix and crystallizes to form reinforcing particles. These particles increase the viscoelasticity of the blends, resulting in improved durability (up to 66-fold) and strength (up to 1.4-fold) of adhesive bonds. At the same time, the growth of viscoelasticity does not lead to a loss of tackiness of the blends, as the application of external force to form an adhesive bond destroys the percolation structure of wax particles. Because of the low specific surface area of wax particles, they increase the durability of adhesive joints worse than silica (in 380-fold) or organoclay particles (in 3300-fold). However, the use of polyethylene wax allows reducing melt viscosity by 4–5 decimal orders of magnitude in the case of highly filled adhesives.

Pattern of Head Injuries in Western Hilly Region of Nepal: A Hospital-based Cross-sectional Study

Introduction: Subtle or gross structural changes of scalp, skull and its contents due to application of direct or indirect external force are known as head injuries. Head being the most vulnerable and prominent part of body, injuries to it cause major mortality and morbidity globally. This study focussed to find the pattern of traumatic head injuries in patients presented to Lumbini Medical College Teaching Hospital, Palpa, Nepal. Methods: The data was collected from 252 patients (164 males and 88 females) with head injuries attending Emergency or out-patient department of Neurosurgery of the institute. All patients with traumatic head injuries (scalp injury, skull fracture, intracranial haemorrhage and brain injury) were included in the study and brought dead patients and patients with non-traumatic brain lesions were excluded. Results: Among the various modes of head injuries, the most frequent was road traffic accidents accounting 125 (49.60%) cases and fall from height 108 (42.86%) cases was second to it followed by physical assault 12 (4.76%) and others 7(2.78%). Manner of injuries were unintentional in 238 (94.44%) of cases. Among males, intentional injuries were present in 5 (2.98%) cases and among females, 9 (10.72%) cases presented with intentional injuries. In 105 (41.67%) of the cases, head injuries were associated with injuries to the other body parts as well. Conclusion: The most common cause of head injury was found to be road traffic accident followed by fall from height. Intentional injuries were more common in females when compared to males.

Biological cells and coupled electro-mechanical effects: The role of organelles, microtubules, and nonlocal contributions

Biological cells are exposed to a variety of mechanical loads throughout their life cycles that eventually play an important role in a wide range of cellular processes. The understanding of cell mechanics under the application of external stimuli is important for capturing the nuances of physiological and pathological events. Such critical knowledge will play an increasingly vital role in modern medical therapies such as tissue engineering and regenerative medicine, as well as in the development of new remedial treatments. At present, it is well known that the biological molecules exhibit piezoelectric properties that are of great interest for medical applications ranging from sensing to surgery. In the current study, a coupled electro-mechanical model of a biological cell has been developed to better understand the complex behaviour of biological cells subjected to piezoelectric and flexoelectric properties of their constituent organelles under the application of external forces. Importantly, a more accurate modelling paradigm has been presented to capture the nonlocal flexoelectric effect in addition to the linear piezoelectric effect based on the finite element method. Major cellular organelles considered in the developed computational model of the biological cell are the nucleus, mitochondria, microtubules, cell membrane and cytoplasm. The effects of variations in the applied forces on the intrinsic piezoelectric and flexoelectric contributions to the electro-elastic response have been systematically investigated along with accounting for the variation in the coupling coefficients. In addition, the effect of mechanical degradation of the cytoskeleton on the electro-elastic response has also been quantified. The present studies suggest that flexoelectricity could be a dominant electro-elastic coupling phenomenon, exhibiting electric fields that are four orders of magnitude higher than those generated by piezoelectric effects alone. Further, the output of the coupled electro-mechanical model is significantly dependent on the variation of flexoelectric coefficients. We have found that the mechanical degradation of the cytoskeleton results in the enhancement of both the piezo and flexoelectric responses associated with electro-mechanical coupling. In general, our study provides a framework for more accurate quantification of the mechanical/electrical transduction within the biological cells that can be critical for capturing the complex mechanisms at cellular length scales.

Examination of CVFEM for nanofluid free convection MHD flow through permeable medium

In current attempt, a numerical code was developed to model the nanofluid free convected magnetized flow by porous cavity. Non-Darcy formula is carried out to include the term of porosity in momentum expression. Radiative phenomenon is reported for distinct nanoparticle shapes. Aspects of radiative constraint, shape factor, Rayleigh number, magnetic force, and nanoparticles’ shape on nanofluid magneto-hydrodynamic natural convection are analyzed. Result demonstrated that application of external magnetic force deteriorates the convection and this reduction is more perceptible at the greater permeability. The conductive heat transport is the dominating form of heat transportation under the impact of higher magnetic force. For the constant values of Rayleigh, Hartmann’s and Darcy number, $${\text{Nu}}_{{{\text{avg}}}}$$ is independent of shape factor and observes a direct association with the radiation parameter.