Mean Bending Research Articles

Performance assessment of multi-source GNSS radio occultation from COSMIC-2, MetOp-B/C, FY-3D/E, Spire and PlanetiQ over China

Global Navigation Satellite System (GNSS) radio occultation (RO) is one of the most crucial observations in atmospheric and climate science. GNSS RO globally produces accurate and long-term stable vertical profiles for essential climate variables with high vertical resolution in all weather conditions. RO measurements offer global coverage but may be limited for specific regions. Currently, various RO satellite constellation programs have been developed by nations and companies, and the growing quantity of RO observations can contribute not only globally but also has the potential to benefit specific regions, such as China. To investigate the potential of RO observation in China, the performance of five operational RO measurements from COSMIC-2, MetOp-B/C, FY-3D/E, Spire and PlanetiQ on data coverage capabilities and quality are assessed by comparing with ERA5 and radiosonde over China. The results of data coverage showed that all RO missions can acquire extensive coverage over China with effective low-altitude penetration capability, whereas MetOp-B/C exhibits some gaps in local time coverage. The results of data quality confirmed that commercial Spire and PlanetiQ are comparable to those of national-led COSMIC-2, MetOp-B/C and FY3D/E, even though Spire exhibited a lower signal-to-noise ratio (SNR). The mean bending angle and refractivity relative differences of all RO measurements are within ±0.53/1.30 % and ± 0.54/0.28 % (with respect to ERA5/radiosonde) in the altitude range of 5 to 35 km, respectively, and the corresponding relative standard deviations (SD) are less than 2.20/6.99 % and 1.35/1.56 %, respectively. Mean temperature and specific humidity differences of all RO measurements are within ±0.18/0.22 K and ± 0.08/0.22 g/kg, respectively, from the near-surface to 12 km, with SD of less than 1.26/1.67 K and 0.84/0.91 g/kg. Among the five RO missions, FY-3D/E exhibits larger errors in refractivity, temperature and specific humidity. The RO profiles derived from GPS, GLONASS, BeiDou and Galileo show comparable quality at the altitudes below 35 km. These results can help users further understand the capabilities and performance of these RO observations and indicate the application potential of numerous RO profiles from multi-source RO measurements, which is anticipated to enhance numerical weather predictions for China.

Mechanical performance of patient-specific prefabricated temporary shell versus laboratory-fabricated CAD/CAM provisional implant-supported single-tooth restorations: Alaboratory study.

To evaluate the mechanical performance of patient-specific prefabricated temporary shell versus laboratory-fabricated CAD/CAM provisional restorations on titanium temporary abutments, with and without thermo-mechanical ageing. Implants with a conical connection were divided into four groups (n = 24) and restored with temporary shell or laboratory-fabricated central or lateral incisor PMMA restorations that were relined or bonded on titanium temporary abutments. The diameter of the central and lateral incisor groups' implants was regular (ϕ 4.3 mm) or narrow (ϕ 3.5 mm), respectively. Half of each group's specimens were subjected to ageing, simultaneous thermocycling (5-55°C) and chewing simulation (120,000 cycles, 50 N, 1.7 Hz) resulting in eight groups in total (n = 12). The aged specimens were evaluated with optical microscopy, and survival and complication rates were determined according to modified USPHS criteria. The non-aged specimens and those that had survived ageing were loaded until failure, whereupon bending moments were calculated. Survival rates after ageing were 100% for all groups. Apart from wear facets (ϕ 2-3 mm) on the palatal restoration surface, no complications were observed. The mean fracture load and bending moments ranged between 597.6-847.1 N and 433.3-550.6 Ncm, respectively, with no significant differences between the eight groups (p = .25; p = .20). As patient-specific temporary shell central and lateral incisor provisional implant-supported restorations are mechanically stable enough to withstand clinical bite forces, even after thermo-mechanical ageing, they may serve as an alternative to laboratory-fabricated provisional restorations.

Biomechanical Consequences of Proximal Screw Placement in Minimally Invasive Surgery for Hallux Valgus Correction

Hallux valgus is one of the most common surgically corrected forefoot deformities. Studies evaluating clinical outcomes of minimally invasive chevron and akin (MICA) procedure have shown shorter operation time, faster recovery, and smaller scars compared to the open approach. Previous biomechanical cadaveric studies have largely focused on the open approach with minimal on MICA. To our knowledge, no studies have compared different proximal screw placements in MICA which can either be three-point fixation or intramedullary. This study aims to compare the biomechanical properties of fixation between these 2 techniques in MICA. Six matched pairs of human fresh frozen cadaveric feet were randomized to either 3-point fixation or intramedullary groups. Both procedures were performed by a single fellowship-trained orthopedic foot and ankle surgeon. Using a material testing machine, each specimen underwent 1000 cycles of plantar-to-dorsal uniaxial loads from 0 to 31 N in cantilever configuration while monitoring bending stiffness and distal fragment dorsal angulation. They were then subjected to load until failure at a compression rate of 10 mm/min. Specimens from both groups tolerated the walking fatigue test. Mean bending stiffness of 3-point fixation was 84% higher than intramedullary constructs (p = .002). Mean dorsal angulation of intramedullary was thrice that of 3-point fixation constructs (p = .008). Mean load to failure of 3-point fixation was 30% higher than intramedullary constructs (p = .001). Three-point fixation provide superior biomechanical stability compared to intramedullary proximal screw placement. The surgical technique using 3-point proximal screw fixation can offer robust fixation and lead to better clinical outcomes.

Patterning of multicomponent elastic shells by gaussian curvature.

Recent findings suggest that shell protein distribution and the morphology of bacterial microcompartments regulate the chemical fluxes facilitating reactions which dictate their biological function. We explore how the morphology and component patterning are coupled through the competition of mean and gaussian bending energies in multicomponent elastic shells that form three-component irregular polyhedra. We observe two softer components with lower bending rigidities allocated on the edges and vertices while the harder component occupies the faces. When subjected to a nonzero interfacial line tension, the two softer components further separate and pattern into subdomains that are mediated by the gaussian curvature. We find that this degree of fractionation is maximized when there is a weaker line tension and when the ratio of bending rigidities between the two softer domains ≈2. Our results reveal a patterning mechanism in multicomponent shells that can capture the observed morphologies of bacterial microcompartments, and moreover, can be realized in synthetic vesicles.

Predicting out-of-plane bending strength of cross laminated timber: Finite element simulation and experimental validation of homogeneous and inhomogeneous CLT

The strength of cross laminated timber (CLT) depends on the stiffness and strength of the lamellas and on the strength of the finger joints. A model for how stiffness and strength vary along and between lamellas is used in combination with a finite element model of CLT and Monte Carlo simulations to calculate out-of-plane bending strength of homogeneous and inhomogeneous CLT. Calculated and experimentally obtained results of characteristic bending strengths, coefficient of variation of bending strength and the proportion of finger joint failures, agree very well for both types of CLT. The characteristic out-of-plane bending strength and the mean bending stiffness were 23% and 16% higher, respectively, for inhomogeneous CLT with outer layer lamellas graded in the strength class C35, compared to homogeneous CLT with all lamellas graded in the class C24. Simulation results give basis for simple equations by which bending strength of CLT can be determined as function of the layup, the strength class of outer layer lamellas and characteristic strength of the finger joints. Furthermore, system effects are investigated. For inhomogeneous CLT, with outer layer lamellas of high strength class, the system effects turn out to be quite different from those of ordinary, homogeneous CLT.

Analyzing the Time Evolution of a Particle by Decomposes the Initial State Confinement in 1D Well into the Lowest Eigenstates Energy

In this work, we obtained the time evolution of the wave function of a limited quantum system (1D Box), hence getting a mathematical model to describe the system. By using programming computes, it performs a time evolution that decomposes the initial state into the 2,10, and 20 lowest energy eigenstates. Finally, by comparing numerical de-composition coefficients for the wave function to the analytical values, it found the number of knots increases directly versus the energy of the particle's quantum state. As a result, the mean bending given by the second derivative which is proportional to the kinetic energy operator should increase. We found there is a negligible mean and standard deviation of the energy in units of the ground state energy.

Enhancing the Weld Quality of Polylactic Acid Biomedical Materials Using Rotary Friction Welding.

Polylactic acid (PLA) stands out as a biomaterial with immense potential, primarily owing to its innate biodegradability. Conventional methods for manufacturing PLA encompass injection molding or additive manufacturing (AM). Yet, the fabrication of sizable medical devices often necessitates fragmenting them into multiple components for printing, subsequently requiring reassembly to accommodate the constraints posed by the dimensions of the AM platform. Typically, laboratories resort to employing nuts and bolts for the assembly of printed components into expansive medical devices. Nonetheless, this conventional approach of jointing is susceptible to the inherent risk of bolts and nuts loosening or dislodging amid the reciprocating movements inherent to sizable medical apparatus. Hence, investigation into the joining techniques for integrating printed components into expansive medical devices has emerged as a critical focal point within the realm of research. The main objective is to enhance the joint strength of PLA polymer rods using rotary friction welding (RFW). The mean bending strength of welded components, fabricated under seven distinct rotational speeds, surpasses that of the underlying PLA substrate material. The average bending strength improvement rate of welding parts fabricated by RFW with three-stage transformation to 4000 rpm is about 41.94% compared with the average bending strength of PLA base material. The average surface hardness of the weld interface is about 1.25 to 3.80% higher than the average surface hardness of the PLA base material. The average surface hardness of the weld interface performed by RFW with variable rotational speed is higher than the average surface hardness of the weld interface performed at a fixed rotating friction speed. The temperature rise rate and maximum temperature recorded during RFW in the X-axis of the CNC turning machine at the outer edge of the welding part surpassed those observed in the internal temperature of the welding part. Remarkably, the proposed method in this study complies with the Sustainable Development Goals due to its high energy efficiency and low environmental pollution.

Determination of Bending Moment Resistance of L-Type Doweled Joints Reinforced With Glass-Fiber-Reinforced Polymer Woven Fabrics (GFRPWF) and Basalt-Fiber-Reinforced Polymer Woven Fabrics (BFRPWF)

In this study investigated the bending moment resistance of L-type doweled joints reinforced with glass-fiber-reinforced polymer woven fabrics (GFRPWF) and basalt-fiber-reinforced polymer woven fabrics (BFRPWF). Dowels produced from Scots pine, oak, beech and chestnut wood were used in the doweled joints. While the GFRPWF and BFRPWF were fixed with epoxy adhesive, the dowels were fixed with polyvinyl acetate (PVAc-D3/D4) glue. Test were carried out to determine the bending moment resistance of doweled joints. Experimental results showed that joints connected with oak dowel has been the highest bending moment resistance, and the joints of Scots pine dowel has been the weakest bending moment resistance. The bending moment resistance of oak dowel was approximately 23%, 33%, and 61% higher than for joints constructed with beech, Chestnut and Scots pine, respectively. The bending moment resistance value reinforced with the BFRPWF (55.62 N.m), and the lowest was in unreinforced joints (32.06 N.m). The mean bending moment resistance of reinforced joints (GFRPWF, BFRPWF) was 31% and 74% higher than unreinforced samples (control), respectively. In general, it has been found that the bending moment resistance of doweled joints is influenced by wooden dowel species and FRP types.

Effect of wing planform on plunging wing aerodynamics

The unsteady aerodynamics of three plunging wings with different planform shapes was investigated in water tunnel experiments by means of force/moment and three-dimensional volumetric velocity measurements at a post-stall angle of attack. In contrast with a rectangular wing, a tapered wing does not exhibit a local minimum of the time-averaged lift coefficient at a reduced frequency of k≈ 1.7. This is due to the oblique shedding of trailing-edge vortices, which prevents the coupling with leading-edge vortices. The wing with a round-tip exhibits the same double maxima that correspond to the subharmonic and the fundamental frequency of vortex shedding in steady freestream. However, combined leading-edge and tip vortex produce larger time-averaged lift force with increasing reduced frequency. The variation of the bending moment is similar to that of the lift force in general. However, the mean bending moment arm shifts outboard with increasing reduced frequency due to the increased three-dimensionality of the vortex filaments and the tip-vortex effect. Maximum lift and bending moment become more similar for all three wings at higher reduced frequencies as the added mass effect becomes more significant.

Basic Mechanical Properties of Laminated Flattened-Bamboo Composite: An Experimental and Parametric Investigation

To reduce carbon emissions in the construction industry, more and more researchers have paid attention to engineered bamboo, a natural and green material. This research focused on laminated flattened-bamboo (LFB), a new bamboo composite produced by the advanced non-notched flattened-bamboo technology which can improve the utilization rate of bamboo and reduce production costs by reducing the use of adhesive compared with the gluing process of conventional bamboo laminates. The basic mechanical properties under compression, tension, three-point bending, and shearing of LFB in three orthogonal directions were mainly studied. Experimental results showed that compressive and tensile strength (modulus) along the grain direction were 56.2 MPa (9,542.7 MPa) and 106.9 MPa (10,151.1 MPa), respectively; in the radial direction were 43.1 MPa (580.9 MPa) and 1.8 MPa (1,459.6 MPa), respectively; in the tangential direction were 19.0 MPa (1,124.5 MPa) and 4.3 MPa (5,112.5 MPa), respectively; the mean bending strength (modulus) was 80.8 MPa (8,076.8 MPa), and the shear strength (modulus) was 17.3 MPa (1,878.8 MPa). The measured properties were comparable to that of other structural bio-based materials, showing LFB has the potential to be an alternative to timber in future construction applications. The modulus and Poisson’s ratio was analyzed, and the result showed that LFB could be regarded as orthotropic material approximately. The failure types under various loading conditions were summarized. Based on the Ramberg Osgood relation, the stress-strain models of LFB composite under compression, tension, and shearing were proposed, and the characteristic value of ultimate strength and elastic modulus was determined by parametric analysis.

Mechanical qualification and microstructural analysis of alumina produced by material extrusion

Ceramics with their advantageous properties such as high thermal conductivity and electrical insulation are attractive to circuit carrier materials in electronics production. Using material extrusion (MEX-AM) for reasons of flexible manufacturing, this work produces green bodies with low surface roughness, which is necessary for subsequent metalizing to create 3D circuit carriers. Systematic variation of post-treatment profiles (debinding, sintering) leads to different microstructures and thus influences mechanical properties. A comprehensive mechanical qualification of ceramic samples produced with MEX-AM and post-treated differently has been carried out, in which tensile, compressive and flexural strength are analyzed. Using the Anderson Darling Test, it is shown that statistical methods standardized for conventional ceramics are applicable to additively manufactured specimens. A mean bending fracture strength comparable to conventional ceramics could be achieved combining a low heating rate profile for debinding with a two-step sintering (TSS) approach, which resulted in reduction of grain size, as SEM analysis confirmed.

Evaluation of rectus abdominis muscle strength and width of hernia defect in patients undergoing incisional hernia surgery.

The aim of this study was to analyze the strength status of the rectus abdominis muscle in patients with incisional hernia and the relationship between the width of the hernia defect and the strength of the rectus abdominis muscle. This is a observational cohort study of patients with medial line incisional hernia (July-October 2022), classified as W2 according to the European Hernia Society (EHS). The data collected were demographic and clinical characteristics related to hernia, and measure of the rectus abdominis muscle strength using an isokinetic dynamometer and a strain gauge. We analyzed the relationship between hernia width and rectus abdominis muscle strength with correlation tests to adjustment by age, sex, BMI, and body composition. A total of 40 patients (64% female) with a mean age of 57.62years (SD 11) were enrolled in the study. The mean BMI was 29.18 (SD 5.06), with a mean percentage of fat mass of 37.8% (SD 8.47) and a mean percentage of muscle mass of 60.33% (SD 6.43). The maximum width of the hernia defect was 6.59cm (SD 1.54). In the male group, the mean bending force moment (ISOK_PT) was 94.01Nwm (SD 34.58), bending force moment relative to body weight (ISOK_PT_Weight) was 103.32Nwm (SD 37.48), and peak force (PK_90) was 184.71 N (SD 47.01). In the female group, these values were 58.11Nwm (SD 29.41), 66.48Nwm (SD 32.44), and 152.50 N (SD 48.49), respectively. Statistically significant differences were observed in the relationship between the data obtained with the isokinetic dynamometer and sex (p = 0.002), as well as between the data obtained with the isokinetic dynamometer and age (p = 0.006). Patients in the 90th percentile (P90) of rectus abdominis muscle strength also had smaller hernia defect widths (p = 0.048). In this study, age and sex were identified as the most statistically significant predictor variables for rectus abdominis muscle strength. The width of the hernia defect exhibited a trend towards statistical significance.

Vibration of Conjugated Shell Systems Under Combined Static Loads

We propose a mathematical model of vibration of elastic systems formed by conjugated shells of revolution with different geometry in the field of combined static axisymmetric loads. The model is based on the concepts of geometrically nonlinear theory of mean bending and realized within the framework of the classical Kirchhoff–Love theory with the use of contemporary methods of applied mathematics and numerical analysis. The spectral picture of a shell structure with elements of positive, zero, and negative Gaussian curvature is constructed. This picture enables us to detect resonance situations under specific dynamic actions and determine dangerous combinations of static loads in the analysis of stability of the equilibrium states of the structure.

An MCL internal brace can withstand cyclic fatigue loading and produce a valgus load to failure similar to that of intact knees.

The purpose of this study is to report on the biomechanical durability and strength of an MCL internal brace construct. The null hypothesis is that there will be no difference between this construct and the intact MCL in terms of deflection during fatigue testing and the ultimate failure load. Eight cadaver knees were used. A grade 3 equivalent MCL tear was created with both the superficial and deep femoral MCL severed. An internal brace was created by placing a cortical button and loop through the center of the femoral MCL origin and secured on the lateral cortex of the distal femur. A FiberTape (Arthrex, Naples, FL) was looped through the cortical button loop and was secured in the center of the tibial insertion of the MCL. After pre-cycling, the specimens underwent 1000 cycles of compressive load between 100 and 300N, using four point bending testing into direct valgus. Pre and post testing deflection was measured using three dimensional motion data from two sets of reflective markers. A load-to-failure test was then conducted with failure defined as the first significant decrease in the load-displacement curve. The mean increase in deflection between pre- and post-testing was 0.6° (SD ± 0.3°). The mean failure bending moment was 122.4 Nm (SD ± 29 Nm). The internal brace construct employed in this study was able to withstand cyclic fatigue loading and recorded a valgus load to failure similar to that of intact knees. It is important for clinicians who are considering using this commercially available technique to be aware of how the construct performs under cyclic loading compared to the intact MCL.

How to Train Your Posture: Haptic Feedback Can be Used for Postural Adaptation of the Trunk During Upper-Limb Motor Training.

Poor trunk posture, especially during long periods of sitting, could lead to problems such as Low Back Pain (LBP) and Forward Head Posture (FHP). Typical solutions are based on visual or vibration-based feedback. However, these systems could lead to feedback being ignored by the user and phantom vibration syndrome, respectively. In this study, we propose using haptic feedback for postural adaptation. In this two-part study, twenty-four healthy participants (age 25.87 ± 2.17 years) adapted to three different postural targets in the anterior direction while performing a unimanual reaching task using a robotic device. Results suggest a strong adaptation to the desired postural targets. Mean anterior trunk bending after the intervention is significantly different compared to baseline measurements for all postural targets. Additional analysis of movement straightness and smoothness indicates an absence of any negative interference of posture-based feedback on the performance of reaching movement. Taken together, these results suggest that haptic feedback-based systems could be used for postural adaptation applications. Also, this type of postural adaptation system can be used during the rehabilitation of stroke patients to reduce trunk compensation in lieu of typical physical constraint-based methods.

Efficacy of Deep Brain Stimulation for Camptocormia in Parkinson's Disease: A Systematic Review and Meta-Analysis.

Camptocormia is one of the most common postural disorders of Parkinson's disease (PD) which has limited treatment options. In this review, we summarize the efficacy of deep brain stimulation (DBS) for camptocormia in PD. The PubMed (https://pubmed.ncbi.nlm.nih.gov/) and EMBASE databases (https://www.embase.com/) were searched for the terms "Parkinson Disease" and "camptocormia" in combination with "deep brain stimulation". We then explored the efficacy of DBS for camptocormia by statistical analysis of the bending angle, the Unified Parkinson's Disease Rating Scale III (UPDRS-III) and L-dopa equivalent daily dose (LEDD), and by evaluating the prognosis after DBS. Twenty articles that reported results for 152 patients were included in this review. These comprised 136 patients from 16 studies who underwent subthalamic nucleus deep brain stimulation (STN-DBS), and 13 patients from 3 studies who underwent globus pallidus internus deep brain stimulation (GPi-DBS). One study used both STN-DBS (2 patients) and GPi-DBS (one patient). After 3-21 months of follow-up, the mean bending angle during the Off-period was significantly reduced compared to pre-DBS (31.5 ± 21.4 vs. 53.6 ± 22.7, respectively; p < 0.0001). For the STN-DBS trials, the mean post-operative bending angles during both Off- and On-periods were significantly reduced compared to pre-operative (32.1 ± 22.7 vs. 55.4 ± 24.1, p = 0.0003; and 33.1 ± 21.5 vs. 43.7 ± 20.6, p = 0.0003, respectively). For GPi-DBS, the mean bending angle post-DBS during the Off-period was considerably lower than pre-DBS (28.5 ± 10.7 vs. 42.9 ± 9.9, p < 0.001). The decrease in bending angle after DBS was negatively correlated with the duration of camptocormia (R = - 0.433, p = 0.013), whereas positively associated with the pre-bending angle (R = 0.352, p = 0.03). DBS is an effective treatment for camptocormia in PD. Patients in the early stage of camptocormia with more significant bending angle may benefit more from DBS.

Assessing 2 by 6 Southern Pine Lumber Flexural and Tensile Properties with Nondestructive Techniques

Abstract The objective of this study was to assess the flexural and tensile properties of 702 pieces of No. 2 grade 2 by 6 southern pine lumber using nondestructive testing (NDT) techniques. Longitudinal and transverse vibration techniques were used to test each specimen. The mean dynamic modulus of elasticity in the longitudinal direction was 11,246 MPa, and the mean transverse vibration dynamic modulus of elasticity was 11,491 MPa. Proof-loading bending tests were conducted on each specimen. The mean bending modulus of elasticity (MOE) was 10,615 MPa. Each specimen was then destructively tested in tension parallel to the grain to determine tension MOE (Et) and ultimate tensile stress (UTS). The overall mean for Et was 11,339 MPa and the UTS mean was 28.54 MPa. Correlations between growth characteristics, and physical and mechanical properties were analyzed. From the linear regression analysis, a strong relationship between Et and dynamic MOE was found using both NDT tools. Multivariable regression models were developed to improve UTS estimation. NDT techniques are recommended for the estimation of mechanical properties of No. 2 grade 2 by 6 southern pine lumber.

Mean wake and aerodynamic forces for surface-mounted finite-height square prisms of very small aspect ratio

The mean flow field, aerodynamic forces, bending moment and Strouhal number (St) were investigated for isolated surface-mounted finite-height square prisms of very small aspect ratio (AR). The Reynolds number was Re =7.5×104 for the velocity measurements and 9×104 for the force, bending moment and St measurements. Prisms with AR = 0.5, 0.7 and 1 were considered, under two different boundary layer thicknesses of δ/D=0.7–0.8 (thin) and δ/D=1.3 (thick). For both boundary layers, the mean drag force coefficient showed a sharper increase with AR compared with taller prisms, and the mean normal force coefficient increased smoothly, with a lower magnitude than pressure-based normal force coefficients. An approximately constant point of action of the drag force was found for AR &amp;lt; 1. While the thick boundary layer caused the spectral peaks to weaken and St to decrease, some periodicity was still found for all AR. These features were connected to the changes in the mean wake of the prisms with AR and δ/D. A smaller AR and larger δ/D had similar effects, causing the wake to shorten, the probability and type of reattachment of the flow on the free end to change, and the mean wake structure to transition from a streamwise wake vorticity pattern to an inner vorticity pattern. The prism with AR = 1 showed a dipole wake structure similar to that of taller prisms, while the unique wake topology of prisms with AR &amp;lt; 1 was found to be responsible for the different force and St trends identified in this range of AR.

Flagellar Propulsion of Sperm Cells Against a Time-Periodic Interaction Force.

Sperm cells undergo complex interactions with external environments, such as a solid-boundary, fluid flow, as well as other cells before arriving at the fertilization site. The interaction with the oviductal epithelium, as a site of sperm storage, is one type of cell-to-cell interaction that serves as a selection mechanism. Abnormal sperm cells with poor swimming performance, the major cause of male infertility, are filtered out by this selection mechanism. In this study, collinear bundles, consisting of two sperm cells, generate propulsive thrusts along opposite directions and allow to observe the influence of cell-to-cell interaction on flagellar wave-patterns. The developed elasto-hydrodynamic model demonstrates that steric and adhesive forces lead to highly symmetrical wave-pattern and reduce the bending amplitude of the propagating wave. It is measured that the free cells exhibit a mean flagellar curvature of 6.4 ± 3.5 radmm-1 and a bending amplitude of 13.8 ± 2.8 radmm-1 . After forming the collinear bundle, the mean flagellar curvature and bending amplitude are decreased to 1.8 ± 1.1 and 9.6 ± 1.4 radmm-1 , respectively. This study presents consistent theoretical and experimental results important for understanding the adaptive behavior of sperm cells to the external time-periodic force encountered during sperm-egg interaction.

A comparison of the effect of different forms of Graphene and Polyvinylpyrrolidone on physically strengthening PMMA

Aim: The aim of this study was to compare the effects of powder, mat, and sheet forms of graphene and polyvinylpyrrolidone (PVP) on the bending strength of polymethyl methacrylate (PMMA). Methodology: A total of 75 PMMA samples (64 x 13 x 3 mm) were obtained and separated into five groups of 15, one of which was the control group. No strengthening material was added to the control group samples. In the PMMA+Polyvinylpyrrolidone powder (PVPP) (Group B) and PMMA+Graphene powder (GP) groups (Group D), PVP (0.5%) and graphene (0.01%) powders, respectively were added to the PMMA. In the PMMA+Polyvinylpryrolidone fiber mat (PVPM) (Group C) and PMMA+Graphene sheet (GS) groups (Group E), a PVP mat and graphene sheet, respectively were placed in the center of a square PMMA resin mold. To measure the samples’ resistance to bending, the three-point bending test (ISO 1567) was applied. Fracture lines were examined under a scanning electron microscope (SEM), and bending strength was analyzed using one-way analysis of variance (ANOVA). Results: A statistically significant difference was determined between the GS (118.5093 ± 11.94859 Mpa) and PVPP (105.5267 ± 6.80595 Mpa) groups. The mean bending resistance values were numerically higher in the PVPM (115.8487 ± 17.15440), GS (118.5093 ± 11.94859), and GP (116.2680 ± 16.03207) groups compared to the control group (108.2407 ± 24.23104). The graphene sheets and PVP mats showed higher resistance to bending than the powder form of either material. Conclusion: In clinical dental prosthesis use, PVP mats and graphene sheets are preferable with respect to both PMMA strengthening and color. How to cite this article: Mutluay Ünal S. A comparison of the effect of different forms of Graphene and Polyvinylpyrrolidone on physically strengthening PMMA. Int Dent Res 2022;12(2):62-9. https://doi.org/10.5577/intdentres.2022.vol12.no2.4 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.