Significant Reduction In Stiffness Research Articles

Comparative analysis of mechanical characteristics in masonry walls: impact of aspect ratios and opening percentages

In this research, we undertake an extensive investigation focusing on masonry walls with aspect ratios of one and two, both confined and unconfined, while also accounting for a range of opening percentages. Employing a combination of finite element analysis and a simplified micro-modeling approach, we meticulously scrutinized and validated several masonry wall with an objective to investigate effects of aspect ratios and varying percentages of openings on key seismic characteristics such as lateral capacity, stiffness, and failure modes. Results reveal that with openings, wall lateral stiffness reduced by up to 54%. For a 4% opening, aspect ratio 1.0 walls saw reductions of 53.9% (unconfined) and 26.0% (confined). Aspect ratio 2.0 walls experienced 50.8% (unconfined) and 52.3% (confined) reductions. Notably, confined aspect ratio 2.0 walls showed significant stiffness reduction compared to aspect ratio 1.0 walls. Results highlight aspect ratio one walls’ superior performance over aspect ratio two walls in both confined and unconfined conditions. A four-parameter logistic regression quantifies opening percentages’ impact on lateral stiffness. This equation aids design professionals, enabling cost-effective and sustainable decision-making before construction.

Biceps brachii elastography in well-trained men post eccentric exercise-induced muscle damage.

Recent advancements in elastography techniques, specifically supersonic shearwave elastography (SWE), have enabled non-invasive assessment of muscle stiffness. However, there is limited research on the immediate and short-term effects of eccentric exercise-induced muscle damage (EIMD) in well-trained individuals. This study aimed to follow up on the effects of eccentric training on the biceps brachialis stiffness by supersonic shearwave imaging (SSI) as well as the soreness and elbow flexion maximal voluntary isometric contraction (MVIC), immediately post-intervention, at 10min, 48h, and 96h in well-trained men. Thirteen well-trained males participated in the study. Baseline measurements of elastography images, MVIC of the elbow flexors, and muscle soreness were obtained. The participants performed an eccentric exercise protocol (4 sets X 10 repetitions) on the dynamometer isokinetic and elastography measurements were repeated immediately post-exercise, at 10min, 48h, and 96h. Significant reductions in stiffness (measured by shear modulus (µ)) were observed immediately and at 10min post-exercise. MVIC exhibited significant reductions immediately after, 10min, and 48h compared to baseline measurements. Muscle soreness peaked at 48h, persisting until 96h. The BB stiffness and MVIC reduction immediately post-eccentric exercise in well-trained men, suggest the potential involvement of mechanical stress and sarcomere rupture. Trained individuals may exhibit a distinct response to EIMD compared to untrained individuals, highlighting the applicability of elastography in monitoring acute biomechanical changes following high-intensity exercise.

Hygromechanical Behavior of Polyamide 6.6: Experiments and Modeling.

This paper investigates water absorption in polyamide 6.6 and the resulting hygroscopic swelling and changes in mechanical properties. First, sorption and swelling experiments on specimens from injection molded plates are presented. The observed swelling behavior is dependent on the melt flow direction of the injection molding process. Additionally, thermal analysis and mechanical tensile tests were performed for different conditioning states. The water sorption is accompanied by a decrease in the glass transition temperature and a significant reduction in stiffness and strength. Next, a sequentially coupled modeling approach is presented. A nonlinear diffusion model is followed by mechanical simulations accounting for swelling and concentration-dependent properties. For the mechanical properties, the notion of a "gap" temperature caused by the shift of the glass transition range due to water-induced plasticization is employed. This model enables the computation of local moisture concentration fields and the resultant swelling and changes in stress-strain behavior.

Micromechanical modeling of devulcanized ground tyre rubber, graphene platelets, and carbon black in recycled natural rubber blends

AbstractWaste tyres are a global problem, with 1.5 billion being generated annually. To reduce this problem, a circular economy for tyres should be developed. This requires the incorporation of recycled tyre rubber in tyre products. Yet, most recycled rubber is of insufficient quality. Recycled rubber must react sufficiently well with virgin rubber to be elastically effective in the 3D crosslinked network. Although a broad range of devulcanization techniques have been developed, many recycled‐virgin rubber blends show significant reductions in stiffness compared with their virgin counterparts. This paper demonstrates that micromechanical models for filler reinforcement can be used to evaluate whether recycled rubber behaves in an elastically effective manner. Furthermore, mechanical devulcanization of ground tyre rubber (GTR) by solid‐state shear milling was shown to produce a recycled rubber powder that is elastically effective when blended with virgin natural rubber (vNR). These blends match the equivalent virgin rubber stiffness, despite high‐recyclate content (30/70 vNR/GTR). The addition of nanofillers (carbon black and graphene nanoplatelets) to these blends was evaluated to see how they compared with virgin compounds and filler reinforcement theories. This process may allow for incorporation of devulcanized rubber into existing products, promoting a circular economy for high‐value rubber recycling.

Impact performance of fire-damaged hybrid steel-BFRP reinforcement concrete beams: Influence of area ratio and arrangement of BFRP bars

Hybrid steel-BFRP reinforced concrete (HRC) beams have demonstrated their ability to meet the rigorous demands for both strength and serviceability. However, the mechanical properties of HRC beams under fire accompanied by impact loadings are not yet clear. In order to delve into the impact resistance of HRC beams under high temperatures, a three-dimensional numerical model was crafted to account for both the effects of strain rate and temperature degradation. The study aimed to examine how the impact resistance of HRC beams is influenced by varying area ratios and arrangements of BFRP bars. The model's reliability was ascertained through a comparison between its simulation outcomes and the results of physical tests. The results show that HRC beams exhibit a significant reduction in stiffness, impact and internal force under fire conditions (39 %, 38 % and 72 % for a fire duration of 45 min, respectively). Furthermore, the damage is concentrated in the mid-span. The impact performance of HRC beams at room and high temperatures is between those of pure steel-RC beams and pure-BFRP beams. The variations under the same fire conditions in the displacement and internal force of beams with different BFRP bars area ratios reach 70 %, while with different arrangements of BFRP bars do not differ much (within 20 %). The dynamic to static stiffness ratio and ultimate load ratio is reduced following the growth of BFRP bars area ratio (max. gap up to 56 % and 25 %) and fire time (max. gap up to 15 % and 20 %). Therefore, specimen design prioritizes the bar arrangement with better corrosion resistance. Additionally, the residual bearing capacity of HRC beams is only 10–40 % of the original under 45 min fire duration. The association of residual load capacity and displacement with fire time shifted from linear to nonlinear with rising temperature.

Effect of Plate-Bone Distance and Working Length on 2.0-mm Locking Construct Stiffness and Plate Strain in a Diaphyseal Fracture Gap Model: A Biomechanical Study.

The aim of this study was to determine the effect of plate-bone distance (PBD) and working length on 2.0-mm locking compression plate (LCP) stiffness and strain in four-point bending and torsion in a diaphyseal fracture gap model. A total of 54 LCP with three screws per fragment were assigned to one of nine combinations of working length (WL; short, medium, and long), and PBD (1, 1.5, and 3 mm) for a sample size of six per construct configuration. Stiffness was measured under quasistatic, nondestructive four-point compression bending and torsion. Plate surface strain was recorded using three-dimensional (3D) digital image correlation during four-point compression bending. WL had a significant effect on overall construct stiffness in both compression bending and in torsion, with shorter WL constructs having higher stiffness (p < 0.0001). PBD had no effect on construct stiffness in compression bending; however, a significant reduction in stiffness was noted in torsion (p = 0.047) as PBD incrementally increased. WL had a significant effect on plate strain in compression bending, with shorter WL constructs having lower plate strain (p < 0.0001). PBD had no effect on plate strain in compression bending except for lower plate strain recorded in long WL constructs with 1-mm PBD, compared with 1.5- and 3-mm PBD constructs (p < 0.0001). Longer WL constructs, regardless of PBD, had lower stiffness in compression bending, while in torsion, some modulation of this effect was noted with incremental decreases in PBD. Longer WL resulted in high plate strain, regardless of PBD.

Dynamic Muscle Stimulation for Pain, Tenderness, and Stiffness on Upper Back Muscles: A Novel Approach and Analysis on Shear-wave Elastography

Abstract Upper back myalgia is a complaint of pain, stiffness, and tightness in the upper back muscles. It is characterized by acute or persistent neck–shoulder pain. We report the case of a 24-year-old male who presented with pain and swelling in the neck and upper back region, along with gradual restriction in cervical range of motion (ROM) for 2 months. The pretreatment assessment revealed severe tightness of the middle fibers of the trapezius and upper fibers of the rhomboid major muscle. Pretreatment elastography revealed high elasticity contrast index (ECI) values of 8.59 and 9.01, respectively, and a red region indicative of increased stiffness of the muscle fibers. The patient was treated with Naqvi’s-Dynamic Electrical Therapy Approach (Naqvi’s DELTA) which is a novel method of using interferential current with a dynamic stimulation probe for 15 min using ultrasound gel on the affected area and examining the patient for the effect of the DELTA on muscle elongation by shear wave elastography which is a unique variation in ultrasound imaging. The pre- and posttreatment findings revealed a significant reduction in stiffness of the muscle fibers, indicated by decreased ECI values of 2.14 and 0.94, respectively, in the blue region. In addition, posttreatment also had an impact on pain reduction and a significant increment in the overall cervical ROM.

The underlying mechanisms behind the hydration-induced and mechanical response of spider silk

Spider silk is a unique protein material that exhibits counterintuitive behaviors such as a significant reduction in stiffness of up to three orders of magnitude and a decrease in length of up to ∼60%, commonly termed supercontraction, upon exposure to high relative humidity (RH). In this work a robust free energy-based model is derived for the humidity-induced and mechanical response of spider silk. As opposed to the classical treatment of gels, the penetration of water molecules into a silk network results in an anisotropic response. First, the kinematics that describe the hydration-induced behavior are discussed and the balance laws and equilibrium requirements are reviewed. Next, the balance of free energy is used to derive constitutive relations that relate the free energy-density to the stress, the chemical potential, and the supercontraction stretch that develop in a spider silk fiber. Following experimental observations, a free energy-density that comprises four contributions is proposed: the first two contributions account for the entropic gain and the loss of chain orientation due to water uptake and the consequent dissociation of intermolecular hydrogen bonds, respectively, the third contribution describes the mixing process between the water and the polymer molecules in the silk, and the fourth contribution arises from the supercontraction phenomenon. Explicit forms are proposed for the four free energy-density contributions. The model is validated through a comparison to five different sets of experimental data under different boundary conditions. With an eye to future applications, the response of a spider silk fiber that is radially constrained and subjected to increasing humidity is also explored. The findings from this work pave the way to the design of silk-based composites and biomimetic materials with fascinating non-trivial properties and behaviors.

Endogenous Modulation of Extracellular Matrix Collagen during Scar Formation after Myocardial Infarction

Myocardial infarction is remains the leading cause of death in developed countries. Recent data show that the composition of the extracellular matrix might differ despite similar heart function and infarction sizes. Because collagen is the main component of the extracellular matrix, we hypothesized that changes in inflammatory cell recruitment influence the synthesis of different collagen subtypes in myofibroblasts, thus changing the composition of the scar. We found that neutrophils sustain the proliferation of fibroblasts, remodeling, differentiation, migration and inflammation, predominantly by IL-1 and PPARγ pathways (n = 3). They also significantly inhibit the mRNA expression of fibrillar collagen, maintaining a reduced stiffness in isolated myofibroblasts (n = 4-5). Reducing the neutrophil infiltration in CCR1-/- resulted in increased mRNA expression of collagen 11, moderate expression of collagen 19 and low expression of collagen 13 and 26 in the scar 4 weeks post infarction compared with other groups (n = 3). Mononuclear cells increased the synthesis of all collagen subtypes and upregulated the NF-kB, angiotensin II and PPARδ pathways (n = 3). They increased the synthesis of collagen subtypes 1, 3, 5, 16 and 23 but reduced the expression of collagens 5 and 16 (n = 3). CCR2-/- scar tissue showed higher levels of collagen 13 (n = 3), in association with a significant reduction in stiffness (n = 4-5). Upregulation of the inflammation-related genes in myofibroblasts mostly modulated the fibrillar collagen subtypes, with less effect on the FACIT, network-forming and globular subtypes (n = 3). The upregulation of proliferation and differentiation genes in myofibroblasts seemed to be associated only with the fibrillar collagen subtype, whereas angiogenesis-related genes are associated with fibrillar, network-forming and multiplexin subtypes. In conclusion, although we intend for our findings to deepen the understanding of the mechanism of healing after myocardial infarction and scar formation, the process of collagen synthesis is highly complex, and further intensive investigation is needed to put together all the missing puzzle pieces in this still incipient knowledge process.

In situ formation of core‐shell rubber particles in polypropylene matrix by melt blending and its effects on the toughness and stiffness of the composites

AbstractToughening of thermoplastics with a one‐phase impact modifier generally results in significant reduction in stiffness, whereas core‐shell rubber modifiers have extra structural parameters such as core rigidity and shell flexibility, by controlling which the stiffness and impact toughness of their composites can be better balanced. In this study, three kinds of polyethylene (PE) with different rigidity are used respectively to prepare polypropylene/ethylene–propylene rubber/polyethylene (PP/EPR/PE) ternary composites by melt blending, in which the EPR‐to‐PE ratio is 1:1. Atomic force microscopy‐infrared (AFM−IR) and scanning electron microscopy (SEM) results indicate that core‐shell rubber particles with a PE core and an EPR shell are formed in situ and uniformly dispersed in the PP matrix. Mechanical measurements show that at the same modifier content the PP composites toughened with these core‐shell rubber particles exhibit higher toughness and stiffness than that with EPR alone, and the more rigid the PE core, the greater the effects. These results are in quantitative agreement with a recent theoretical model, providing solid experimental evidence in support of the latter. Furthermore, this work demonstrates an economical approach to toughening PP by partial substitution of the EPR with the much cheaper PE for better performance.

Finite Element Modeling of Internally Actuated Triangular Lattice and Its Variants for Modular Active Cell Robots (MACROs)

Modular Active Cell Robots (MACROs) is an approach for modular robot hardware that leverages simple components such as actuators and compliant joints to make large deformable robotic structures. In this letter, we consider the planar triangular lattice and its sparser variants as the candidate mesh topologies for MACROs. Through Finite Element (FE) simulations, we quantify the deformations obtained for different choices of edges being actuated in the MACRO mesh. Further, we use this data to identify optimal actuation strategies for a target deformation. We demonstrate a trade-off between passive stiffness and actuation energy and thereafter, we refine the triangular lattice by removing edges to reduce the actuation energy without a significant reduction in stiffness. We also identify the refined meshes optimal for desired specifications.

MP04-02 ANALYSIS OF EX-VIVO HUMAN BPH TISSUE TREATED BY HISTOTRIPSY: DOSE AND PARAMETER EFFECTS

You have accessJournal of UrologyCME1 May 2022MP04-02 ANALYSIS OF EX-VIVO HUMAN BPH TISSUE TREATED BY HISTOTRIPSY: DOSE AND PARAMETER EFFECTS Zorawar Singh, Yashwanth N. Kumar, Yak-Nam Wang, Adam Maxwell, Matthew Bruce, Rishi Sekar, Eli Vlaisavljevich, Lawrence D. True, and George R. Schade Zorawar SinghZorawar Singh More articles by this author , Yashwanth N. KumarYashwanth N. Kumar More articles by this author , Yak-Nam WangYak-Nam Wang More articles by this author , Adam MaxwellAdam Maxwell More articles by this author , Matthew BruceMatthew Bruce More articles by this author , Rishi SekarRishi Sekar More articles by this author , Eli VlaisavljevichEli Vlaisavljevich More articles by this author , Lawrence D. TrueLawrence D. True More articles by this author , and George R. SchadeGeorge R. Schade More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002521.02AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Histotripsy is a promising alternative to more invasive procedures for the treatment of benign prostatic hyperplasia (BPH). However, in a phase 1 clinical trial, histotripsy failed to provide objective improvements in urinary function. One explanation may be that the clinical trial pulse parameters, optimized in a canine model, do not translate to more fibrotic human prostates. We aimed to evaluate the efficacy of different histotripsy parameter settings to identify a more efficacious exposure in ex-vivo human BPH tissue (EVHP). METHODS: Deidentified EVHP tissue specimens (n=17) were treated with an 18 element 700kHz cavitation histotripsy transducer, which approximated the device used in the prior clinical trial, and a 1.5MHz boiling histotripsy (BH) transducer. Three different histotripsy exposures were compared: 1) a high pulse repetition frequency (PRF) (approximating the clinical system cavitation cloud histotripsy [CCH]), 2) low PRF CCH and 3) 1Hz PRF BH. Treatment effectiveness was evaluated by measuring pre vs. post treatment Young’s modulus through shear wave elastography (SWE) and histologic analysis (H&E, Masson’s Trichome) of the targeted area. The dose was standardized at 30s/mm and escalated as required to note a significant change in SWE. RESULTS: At the given dose of 30s/mm, BH treatments resulted in a significant 40.1% reduction in SWE Young’s modulus (Figure 1A) p < 0.001. At this dose, neither of the CCH parameter settings (500Hz and 10Hz) resulted in a significant reduction in the Young’s modulus with % changes of differences of 3.1% (p = .83) and -5% (p = .08), respectively. For CCH settings, greater exposure times (up to 90s) did result in significant stiffness reduction of 12.5% (p = 0.04) and 41.1% (p < 0.001) for 500Hz and 10Hz parameter settings, respectively. On histology (Figure 1B), at 30s/mm, the CCH parameter settings resulted in minimal intermittent damage while BH treatments caused near complete ablation. At increasing doses, CCH was also capable of causing complete liquefactive cavity formation. CONCLUSIONS: BH parameters applied in this study resulted in more complete ablation of EVH tissue in comparison to CCH parameters. Additionally, histotripsy treatment parameters similar to those applied with a previous clinical system did not produce consistent ablation of EVHP possibly explaining trial results. Source of Funding: None © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e56 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Zorawar Singh More articles by this author Yashwanth N. Kumar More articles by this author Yak-Nam Wang More articles by this author Adam Maxwell More articles by this author Matthew Bruce More articles by this author Rishi Sekar More articles by this author Eli Vlaisavljevich More articles by this author Lawrence D. True More articles by this author George R. Schade More articles by this author Expand All Advertisement PDF DownloadLoading ...

Immediate effect of stair exercise on stiffness, tone, and pressure pain threshold of thoracolumbar fascia in individuals with lower limb amputation: a preliminary report.

Adaptations to the use of prosthesis in individuals with a lower limb amputation may cause changes in lumbopelvic region structures during daily life activities. To investigate the effect of stair exercise on the stiffness, tone, and pressure pain threshold (PPT) of the thoracolumbar fascia (TLF) in individuals with unilateral lower limb amputation. This is a prospective preliminary study. The study was conducted in Prosthetic Orthotic Centers in Istanbul. Syrian individuals with unilateral transtibial (n = 17) and transfemoral (n = 15) amputation who received prosthesis and rehabilitation services at the centers between February 2020 and December 2020 were included in the study. The subjects were instructed to ascend and descend a nine-step stair one at a time at their maximum possible speed. Measurements were made before and immediately after the stair exercise. Tone and stiffness of TLF was measured using myometer. PPT was measured using algometer. Low back pain was evaluated using numerical pain rating scale. In the transfemoral amputation group, PPT measurements taken immediately after stair exercise were significantly decreased in both the amputated ( P = 0.001) and intact ( P = 0.021) sides, whereas significant reduction in stiffness when compared with the prestair levels was observed only at the intact side ( P = 0.019). The change in PPT values on the amputated side was significantly higher in individuals with transfemoral amputation than those in individuals with transtibial amputation ( P = 0.011). The decrease in PPT values of TLF in the transfemoral amputation group was considered as a precursor sign for low back pain development. Thus, exercises and preventive rehabilitation programs targeting TLF may be needed, especially in this group.

Development of an empirical process model for adjusted porosity in laser-based powder bed fusion of Ti-6Al-4V

A promising approach to address the mismatch of bone and implant stiffness, leading to the stress-shielding phenomenon, is the application of functionally graded materials with adjusted porosity. Although defect formation and porosity in laser-based powder bed fusion of metals (PBF-LB/M) are already widely investigated, so far there is little research on the influences and parameter interactions regarding the pore characteristics. This work therefore aims to provide an empirical process model for the generation of gas porosity in the PBF-LB process of Ti-6Al-4V. Parts with closed locally adjusted porosity of sim 6 % achieved through gaseous pores instead of lack of fusion defects or lattice structures were built by PBF-LB. Parameter variation and evaluation of relative density, pore size and sphericity was done in accordance with the design of experiments approach. A parameter set for maximum gas porosity (laser power of 189 W, scanning speed of 375 mm/s, hatch spacing of 150 μm) was determined for a constant layer thickness of 30 μm and a spot diameter of 35 μm. Tensile tests were conducted with specimens consisting of a core with maximum gas porosity or lack of fusion porosity, respectively, and a dense skin as well as fully dense specimens. Whereas lack of fusion defects can lead to significant reduction of stiffness of 32.2 %, the elastic modulus remained unchanged at 110.0 GPa when implementing spherical pores. Nevertheless, the found superior strength and ductility of specimens with gas porous core (> 1100 MPa and > 0.05 mm/mm, respectively) underline the advantages of adjusted porosity for the application in functionally graded materials and lightweight applications.

Impact of chronic obstructive pulmonary disease on passive viscoelastic components of the musculoarticular system

Chronic obstructive pulmonary disease (COPD) produces skeletal muscle atrophy and weakness, leading to impairments of exercise performance. The mechanical work needed for movement execution is also provided by the passive tension developed by musculoarticular connective tissue. To verify whether COPD affects this component, the passive viscoelastic properties of the knee joint were evaluated in 11 patients with COPD and in 11 healthy individuals. The levels of stiffness and viscosity were assessed by means of the pendulum test, consisting in a series of passive leg oscillations. In addition, to explore the contribution of passive tension in the mechanical output of a simple motor task, voluntary leg flexion–extension movements were performed. Patients with COPD showed a statistically significant reduction in stiffness and viscosity compared to controls. Voluntary execution of flexion–extension movements revealed that the electromyographic activity of the Rectus Femoris and Biceps Femoris was lower in patients than in controls, and the low viscoelastic tension in the patients conditioned the performance of active movements. These results provide novel insights on the mechanism responsible for the movement impairments associated with COPD.

Evaluation of topical therapy of patients with osteoarthritis of small joints of the hands with Voltaren® Emulgel® 2% (diclofenac diethylamine 2%)

To evaluate the efficacy and safety of using the drug Voltaren Emulgel 2% (diclofenac diethylaminе 2%) for 14 days in patients with osteoarthritis (OA) of small joints of the hands. 62 patients of both sexes with hands OA were included in the study, 31 of whom (main group) used Voltaren Emulgel 2% (diclofenac diethylaminе 2%) topically, and the remaining 31 (comparison group) Voltaren Emulgel 2% (diclofenac diethylamine 2%) + oral nonsteroidal anti-inflammatory drugs. The effectiveness of therapy was assessed by using a visual analogue scale (VAS) in dynamics: joint pain and stiffness at rest, pain on movement and during palpation, by functional indices AUSCAN, FIHOA, by assessment of the effect of therapy by the doctor and the patient on a weekly basis. Joint pain decreased after 2 weeks of therapy in all patients during treatment with Voltaren Emulgel 2% (diclofenac diethylamine 2%) in both groups. Significant reduction in stiffness and improvement in hand joint function was achieved after 7 days and lasted until the end of treatment. By the end of treatment, 100% of patients assessed their condition as improvement. Voltaren Emulgel 2% (diclofenac diethylamine 2%) demonstrates comparable clinical efficacy in patients with OA of the hand joints (reduced pain, stiffness and improved joint function) in monotherapy as complex therapy in combination with oral NSAIDS, while being well tolerated.

Intervertebral disc degeneration relates to biomechanical changes of spinal ligaments

BACKGROUND CONTEXTThe ligamentum flavum (LF), the inter- and supraspinous ligament (ISL&SSL) and the intertransverse ligament (ITL) are relevant spinal structures for segmental stability. The biomechanical effect of degeneration and aging on their biomechanical properties remains largely unknown. PURPOSEThe aim of this study was to assess the material properties of the ITL, ISL&SSL and LF and to correlate parameters of biomechanical function with LF-thickness, intervertebral disc (IVD) degeneration and age. STUDY DESIGNBiomechanical cadaveric study. METHODSMRI- and CT-scans of 50 human lumbar segments (Th12-L5) were used to assess the ISL (acc. to Keorochana), the grade of IVD degeneration (acc. to Pfirrmann) and to quantify LF-thickness. The ITL, ISL&SSL and LF were resected in the neutral position of the spinal segment with a specifically developed method to conserve initial strain. Ramp to failure testing was performed (0.5 mm/s) to record initial tension, slack length, stiffness and ultimate strength. The relationship between the biomechanical characteristics and age and radiological parameters were analyzed. There are no study-specific conflicts of interest and no external funding was received for this study. RESULTSWith aging, a significant reduction in initial tension (r=-0.5, p<.01) and ultimate strength (r=-0.41, p<.01) of the LF was observed, while the effect on LF-stiffness and the characteristics of the other ligaments was non-significant. IVD-degeneration was correlated with a significant reduction in stiffness (r=-0.47, p=.001; r=-0.36, p=.01) and ultimate strength (r=-0.3, p=.04; r=-0.36, p=.01) of the LF and ISL&SSL respectively and a significant reduction in initial tension (r=-0.4, p<.01) of the LF. For the ITL, no significant correlation was observed. Comparing Pfirrman 2 to 5, this reduction was 40% to 80% for stiffness 60% to 70% for ultimate strength and 88% for initial tension of the LF. ISL&SSL-stiffness between Kerorochana grade A and D differed significantly (p=.03), while all other comparisons were non-significant (p>.05). LF-thickness did not correlate with the biomechanical properties of the LF (p>.05). CONCLUSIONSAging is primarily related to biomechanical changes to the LF. IVD-degeneration is related to a relevant reduction in stiffness and ultimate strength of the LF and ISL&SSL, with a similar trend for the ITL. The ISL-specific Keorochana grading system provides only minimal biomechanical information and LF-thickness does not provide biomechanical information. CLINICAL SIGNIFICANCEPatient age and the degenerative state of the IVD can be used to evaluate the biomechanical characteristics of the dorsal spinal ligaments, which can be helpful in selecting the optimal surgical procedure (e.g. in decompression surgery) for a specific situation.

Transthoracic ultrasound shear wave elastography for the study of subpleural lung lesions.

PurposeThe aim of this study was to assess whether new-generation shear wave elastography (SWE) is suitable for the characterization of lung subpleural lesions.MethodsIn total, 190 consecutive patients with subpleural lung lesions received ultrasonography and SWE. Patients with suspected malignancy underwent ultrasound-guided transthoracic needle biopsy. Final diagnoses were made on the basis of patients’ clinical course, microbiological studies, and histological results. SWE was also performed in 25 healthy volunteers.ResultsWe found no statistically significant differences in stiffness between lung carcinomas, lung metastases, and pneumonia (P=0.296) or between different histological types of lung cancer (P=0.393). Necrosis was associated with reduced stiffness in pneumonia. Excluding necrotic lesions, pneumonia showed higher stiffness than lung carcinomas (2.95±0.68 m/s vs. 2.60±0.54 m/s, P=0.006). Chronic pneumonia showed increased stiffness (3.03±0.63 m/s), probably due to the presence of fibrotic tissue on histology. Pleural effusion was associated with a statistically significant reduction in stiffness, both in lung carcinomas (P=0.004) and lung metastases (P=0.002). The presence of air in healthy lung tissue may lead to incorrect speed estimates due to shear wave reflection (very high values, 14.64±2.19 m/s).ConclusionTransthoracic SWE could not distinguish lung malignancy from pneumonia, or between different histological types of lung carcinomas. In particular, SWE seems unable to resolve the clinical dilemma of chronic subpleural consolidations.

Experimental Study of the Effect of High Service Temperature on the Flexural Performance of Near-Surface Mounted (NSM) Carbon Fiber-Reinforced Polymer (CFRP)-Strengthened Concrete Beams.

This paper presents a study of the effect of high service temperature (near or beyond glass transition temperature (Tg) of structural epoxy adhesive) on the behavior of near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP)-strengthened reinforced concrete (RC) beams. The study includes experimental work as well as analytical and numerical analysis. To this end, fourteen beams have been tested up to failure in two different series. In series 1, specimens with three different CFRP areas have been tested at two different temperatures (i.e., 20 and 40 °C). In series 2, and with the aim of evaluating the effect of higher temperatures, only one CFRP area was tested under four different temperatures (i.e., 20, 60, 70, and 85 °C). Experimental results are evaluated in terms of load–deflections, failure modes, and bond performance. Furthermore, the experimental load–deflection curves are satisfactorily compared to both analytical predictions and finite element (FE) numerical simulations. In both cases, shrinkage and temperature effects on the short-term response of flexural elements have been accounted for. No significant reduction in stiffness and ultimate load was observed for specimens being tested up to 60 °C (in the range of epoxy Tg), showing FRP rupture failure in all of them. For specimens under 70 and 85 °C, the failure mode changed from FRP rupture to FRP end debonding and concrete crushing, respectively.

Microgravity and Hypergravity Induced by Parabolic Flight Differently Affect Lumbar Spinal Stiffness.

The objective of this study was to determine the response of the lumbar spinal motor control in different gravitational conditions. This was accomplished by measuring indicators of lumbar motor control, specifically lumbar spinal stiffness, activity of lumbar extensor and flexor muscles and lumbar curvature, in hypergravity and microgravity during parabolic flights. Three female and five male subjects participated in this study. The mean age was 35.5 years (standard deviation: 8.5 years). Spinal stiffness of the L3 vertebra was measured using impulse response; activity of the erector spinae, multifidi, transversus abdominis, and psoas muscles was recorded using surface electromyography; and lumbar curvature was measured using distance sensors mounted on the back-plate of a full-body harness. An effect of gravity condition on spinal stiffness, activity of all muscles assessed and lumbar curvature (p’s < 0.007) was observed (Friedman tests). Post hoc analysis showed a significant reduction in stiffness during hypergravity (p < 0.001) and an increase in stiffness during microgravity (p < 0.001). Activity in all muscles significantly increased during hypergravity (p’s < 0.001). During microgravity, the multifidi (p < 0.002) and transversus abdominis (p < 0.001) increased significantly in muscle activity while no significant difference was found for the psoas (p = 0.850) and erector spinae muscles (p = 0.813). Lumbar curvature flattened in hypergravity as well as microgravity, albeit in different ways: during hypergravity, the distance to the skin decreased for the upper (p = 0.016) and the lower sensor (p = 0.036). During microgravity, the upper sensor showed a significant increase (p = 0.016), and the lower showed a decrease (p = 0.005) in distance. This study emphasizes the role of spinal motor control adaptations in changing gravity conditions. Both hypergravity and microgravity lead to changes in spinal motor control. The decrease in spinal stiffness during hypergravity is interpreted as a shift of the axial load from the spine to the pelvis and thoracic cage. In microgravity, activity of the multifidi and of the psoas muscles seems to ensure the integrity of the spine. Swiss (BASEC-NR: 2018-00051)/French “EST-III” (Nr-ID-RCB: 2018-A011294-51/Nr-CPP: 18.06.09).