High Compressive Forces Research Articles

Reporting average glandular dose and its associations with age and exposure parameters

PurposeTo report average glandular dose (AGD) values for the Saudi breast cancer screening program and to examine the relationship between AGD with age and exposure parameters. MethodsScreening mammography of 187,788 exposures were collected. The AGD was calculated per exposure and considering each view (craniocaudal (CC) and mediolateral oblique (MLO)) separately. Spearman correlation, Mann–Whitney U test, and Kruskal-Wallis tests were to test the difference existence in AGD across various age groups and inter- and intra-views (MLO and CC) in acquisition parameters. ResultsThe mean AGD per projection was 1.45 mGy and most AGD falls between 1.3 and 1.5 mGy for both projections which are close in value to those reported to other countries. The participants have a mean age of 49 years. The mean values for the used exposure parameters were 135 N for compression force (CF), 58 mm for compressed breast thickness (CBT), 29 kVp, and 74 mAs. An inverse relation between AGD and age (r = −0.131, p < 0.001) was found. Additionally, AGD was also correlated with CBT (0.39, p < 0.001), and CF (−0.11, p < 0.001). ADG, CBT, CF, mAs, and kVp, were found to have statistically significant differences between CC and MLO (p = 0.001). The CF was the only parameter that had a significant difference between left and right MLOs (p = 0.016). ConclusionWe observed a trend of decreasing AGD with aging in the women of our population. We also noticed that AGD decreases with higher CFs and lower CBTs. A potential explanation for this is that the composition of the breast is changing (glandular tissue reduces) with aging, allowing more CF and thinner CBT leading to less absorbed AGD.

Poster 240: Radiographic and Patient-Reported Outcomes of Patellar Denovo Procedure in Shouldered Versus Unshouldered Patella Cartilage Lesions

Objectives: Unique challenges exist in treating patellar cartilage defects such as the contour of the articular surface and the high dynamic shear and compressive forces at the trochlear articulation. When considering restoration techniques osteochondral autograft or allograft can be used when the underlying bone is also involved but for isolated chondral defects, cell-based restoration is the standard of care. Previous literature has demonstrated that success of these cell-based therapies depends on a fully shouldered, stable rim of healthy cartilage to achieve repair stability. More recently, particulated juvenile articular cartilage (PJAC), minced hyaline cartilage from young donors, has demonstrated promising and practical results in the treatment of symptomatic articular defects of the patella and other surfaces. The newer cell-based techniques are more stable than previous options such as autologous chondrocyte implantation (ACI). The purpose of this study is to compare clinical outcomes of PJAC in patients with shouldered versus unshouldered full-thickness cartilage defects of the patella. We hypothesized that there will be no significant difference in short-term clinical outcomes and radiographic cartilage fill between shouldered and unshouldered lesions. Methods: A retrospective review of prospectively collected data was conducted on patients treated with PJAC for a full-thickness symptomatic patellar cartilage lesion between March 2014 and August 2019. Magnetic resonance imaging (MRI) was performed for all patients at 6, 12, and 24 months postoperatively and analyzed for percent fill, categorized by 0% to 33%, 34% to 66%, and 67% to 100% fill. Patient-reported outcome measures (PROMs) were obtained preoperatively and at 1, 2 and &gt;2 years postoperatively. Arthroscopic images were independently assessed, and cartilage defect characteristics were documented as shouldered or unshouldered by an orthopaedic surgery resident and an orthopaedic surgery sports fellow. Percent fill on MRI and clinical outcome scores (International Knee Documentation Committee, Kujala, Knee injury and Osteoarthritis Outcome Score – Physical Function Short-Form [KOOS-PS], Knee injury and Osteoarthritis Outcome Score – Quality of Life, The Hospital for Special Surgery Pediatric Functional Activity Brief Scale) were analyzed and correlated with the shouldered or unshouldered classification of the lesions. Results: Between March 2014 and August 2019, a total of 70 lesions in 65 patients were treated with PJAC for patellar cartilage lesions. The mean patient age was 26.6 years old (range, 14 – 51) and 76% (n = 53) were female. Twenty-five (36%) knees had undergone prior surgery and average symptom duration was 7.5 years. The average patellar lesion size was 277 mm2 (range, 77 – 800 mm2), the average number of allografts packets used was 2.4 (range, 1 – 5), and the average donor age was 46.1 months (range, 1 – 120). Arthroscopic pictures were available for 64 out of 70 lesions. There was perfect inter-rater reliability of whether the lesions were considered to have a continuous, stable rim (shouldered) or not (unshouldered). Thirty-two lesions were shouldered and the remaining 32 lesions were unshouldered according to their intraoperative pictures. Patients with shouldered lesions reported a significantly lower duration of symptoms than those with unshouldered lesions (5.29 ± 7.12 years vs.10.11 ± 9.85 years, p &lt; 0.05). Patients with shouldered lesions were also significantly more likely to have a prior knee surgery (p &lt; 0.05). Patients did not differ significantly by MRI percent fill in the shouldered versus unshouldered groups (Figure 1). There were no significant differences in baseline, 1-, or 2-year patient-reported outcomes based between patients with shouldered and unshouldered lesions (Table 1). The only statistically significant difference in outcomes was a lower score for KOOS-PS in the unshouldered group at &gt;2 years compared to the shouldered group (p &lt; 0.05), and in the change in KOOS-PS from baseline to 2-years between the 2 groups (p &lt;0.05). Conclusions: Patellofemoral joint cartilage defects are difficult to treat due to their unique thickness and topography. Historically, emphasis has been placed on having a stable, fully shouldered defect in order to achieve success of repair with microfracture or ACI. However, with the increased stability of newer cell-based treatments, these unshouldered cartilage lesions do well both clinically and radiographically. Our study found no significant differences between the shouldered and unshouldered groups with regard to both clinical outcomes as well as radiographic cartilage fill. This suggests that, with newer cartilage restoration techniques, whether a lesion is shouldered does not affect the outcomes achieved by these procedures. [Figure: see text]

Experimental Behavior of a Prototype 3m-Span Modular Glass Pedestrian Bridge

This research is related to the structural performance of a shell-type system made of hollow glass units (HGU) that utilizes glass as the primary structural material. The efficient structural function of the proposed shell-type system is designed using Polyhedral Graphic Statics to achieve a system geometry that maximizes in-plane compression and limits the presence of tension. The large-scale shell structure is constructed using a modular assembly of individual hollow glass units. To date, the research team has completed studies on individual HGU strength and stiffness, and the performance of the interface material necessary to transmit the high in-plane compression forces between neighboring HGUs. As well, the feasibility of the proposed modular system has also been demonstrated through the successful assembly and disassembly of a 3 m span prototype pedestrian bridge known as Tortuca. Tortuca is comprised of 13 individual interlocking HGUs assembled into a compression-dominant form supported on steel abutments. In the current research study, the physical performance of Tortuca is experimentally investigated under controlled laboratory testing and using an extensive assortment of displacement and strain sensors. Significant findings related to experimental testing of Tortuca will be reported.

Mannitol-coated hydroxypropyl methylcellulose as an alternative directly compressible controlled release excipient

One of the most common forms of controlled release technology for oral drug delivery comprises an active ingredient dispersed in a hydrophilic matrix forming polymer such as hydroxypropyl methylcellulose (HPMC), which is tableted via direct compression. However, HPMC may pose problems in direct compression due to its poor flowability. Hence, mannitol syrup was spray-coated over fluidized HPMC particles to produce co-processed HPMC–mannitol at ratios of 20:80, 50:50, and 70:30. Particles of pure HPMC, co-processed HPMC–mannitol, and their respective physical mixtures were evaluated for powder flowability, compression profiles, and controlled release performance. It was found that co-processed HPMC–mannitol consisted of particles with improved flow compared to pure HPMC particles. Sufficiently strong tablets of >2 MPa could be produced at moderate to high compression forces of 150–200 MPa. The dissolution profile could be tuned to obtain desired release profiles by altering HPMC–mannitol ratios. Co-processed HPMC–mannitol offers an interesting addition to the formulator’s toolbox in the design of controlled release formulations for direct compression.

Effect of compressive and tensile forces on glucose concentration and cell viability within the intervertebral disc: A finite element study

Understanding the role of mechanical force on tissue nutrient transport is essential, as sustained force may affect nutrient levels within the disc and initiate disc degeneration. This study aims to evaluate the time-dependent effects of different compressive force amplitudes as well as tensile force on glucose concentration and cell viability within the disc. Based on the mechano-electrochemical mixture theory, a multiphasic finite element model of the lumbar intervertebral disc was developed. The minimum glucose concentration and minimum cell density in both normal and degenerated discs were predicted for different compressive force amplitudes, tensile force, and corresponding creep time. Under high compressive force, the minimum glucose concentration exhibited an increasing and then decreasing trend with creep time in the normal disc, whereas that of the degenerated disc increased, then decreased, and finally increased again. At steady state, a higher compressive force was accompanied by a lower glucose concentration distribution. In the degenerated disc, the minimum cell density was negatively correlated with creep time, with a greater range of affected tissue under a higher compressive force. For tensile force, the minimum glucose concentration of the degenerated disc raised over time. This study highlighted the importance of creep time, force magnitude, and force type in affecting nutrient concentration and cell viability. Sustained weight-bearing activities could deteriorate the nutrient environment of the degenerated disc, while tensile force might have a nonnegligible role in effectively improving nutrient levels within the degenerated disc.

Effect of patient-specific scapular morphology on the glenohumeral joint force and shoulder muscle force equilibrium: a study of rotator cuff tear and osteoarthritis patients.

Introduction: Osteoarthritis (OA) and rotator cuff tear (RCT) pathologies have distinct scapular morphologies that impact disease progression. Previous studies examined the correlation between scapular morphology and glenohumeral joint biomechanics through critical shoulder angle (CSA) variations. In abduction, higher CSAs, common in RCT patients, increase vertical shear force and rotator cuff activation, while lower CSAs, common in OA patients, are associated with higher compressive force. However, the impact of the complete patient-specific scapular morphology remains unexplored due to challenges in establishing personalized models. Methods: CT data of 48 OA patients and 55 RCT patients were collected. An automated pipeline customized the AnyBody™ model with patient-specific scapular morphology and glenohumeral joint geometry. Biomechanical simulations calculated glenohumeral joint forces and instability ratios (shear-to-compressive forces). Moment arms and torques of rotator cuff and deltoid muscles were analyzed for each patient-specific geometry. Results and discussion: This study confirms the increased instability ratio on the glenohumeral joint in RCT patients during abduction (mean maximum is 32.80% higher than that in OA), while OA patients exhibit a higher vertical instability ratio in flexion (mean maximum is 24.53% higher than that in RCT) due to the increased inferior vertical shear force. This study further shows lower total joint force in OA patients than that in RCT patients (mean maximum total force for the RCT group is 11.86% greater than that for the OA group), attributed to mechanically advantageous muscle moment arms. The findings highlight the significant impact of the glenohumeral joint center positioning on muscle moment arms and the total force generated. We propose that the RCT pathomechanism is related to force magnitude, while the OA pathomechanism is associated with the shear-to-compressive loading ratio. Overall, this research contributes to the understanding of the impact of the complete 3D scapular morphology of the individual on shoulder biomechanics.

High Pressure 3 × 30 Minute Compression Methods for Advanced Lower Limb Lymphedema Patients.

Introduction: In advanced lymphedema of lower limbs, stage III bandaging under the routinely applied pressure of 40-60 mmHg remains largely ineffective. This is caused by skin and subcutaneous tissue stiffness due to fibrosis. Edema fluid accumulates deep in the subcutaneous tissue. Evacuating this fluid requires a high external compression force to overcome the resistance of fibrous tissue. We aimed to investigate the effectiveness of the compression method, with high pressure lasting for 3 days. Methods and Results: Twenty-one patients with lower limb lymphedema, stage III, of the postinflammatory type were included. Patients with acute inflammatory symptoms, venous thrombosis, profuse varicose veins, diabetes, and cardiac insufficiency with edema were excluded. A 10-cm-wide rubber bandage was applied to the foot and calf. The interface pressure measured using PicoPress ranged from 58 to 120 mmHg. Skin and deep tissue tonometry, skin water concentration, leg circumference, and drop of interface pressure were measured. Ultrasound examination was done before and after each compression session. The calf circumference decreased by 15.9 ± 5.4%, deep tissue stiffness by 58.9 ± 18.9%, skin stiffness by 69.6 ± 13.5%, and skin water concentration by 43.8 ± 11.5%. Interface pressure dropped to 66.3 mmHg (28-110 mmHg); ultrasonography images showed less fluid in the tissue. Conclusions: High-pressure 30-minute leg compression can remove excess edema fluid within 3 days and enable adjustment of nonstretch compression stockings. This method is more effective in advanced lymphedema at the beginning of therapy than the standard 30-50-mmHg bandaging as it provides an immediate effect.

In Vitro Assessment of Compression Patterns Using Different Methods to Achieve Interfragmentary Compression during Tibial Plateau Levelling Osteotomy.

The aim of this study was to evaluate and characterize different methods to achieve interfragmentary compression during tibial plateau levelling osteotomy (TPLO). TPLO was performed in 20 canine tibia models (Sawbones, Vashon, Washington, United States) using 3D-printed guides for standardization. Interfragmentary compression was assessed using pressure-sensitive films (Prescale, Fujifilm, Atherstone, United Kingdom). Seven compression methods were tested: (1) Kern bone holding forceps clamping the craniodistal aspect of the TPLO plate to the caudal aspect of the tibia (K); (2) using the distal TPLO plate dynamic compression hole (P); (3) pointed bone reduction forceps engaging the caudal aspect of the proximal bone fragment and the cranial aspect of the tibial crest (F); (4) K + P; (5) K + F; (6) F + P; and (7) K + F + P. Five measurements were obtained for each method, and each bone model was used for two measurements (single method, ± plate). The interfragmentary surface was digitalized and divided into quadrants for standardization and pixel density calculation: Q1, craniomedial; Q2, craniolateral; Q3, caudomedial; and Q4, caudolateral. One-way analysis of variance (ANOVA) and post hoc tests were used for statistical analysis. Mean pressures per quadrant differed significantly between methods (p < 0.001). Methods K, F, and P produced more craniomedial, craniolateral, and caudal compression, respectively. Method K resulted in loss of caudal compression (p < 0.001). Method F + P provided the most even distribution of high interfragmentary compression forces. The addition of method K to this construct (K + F + P) marginally increased cranial compression (p = 0.189 for Q1; p < 0.001 for Q2), but reduced compression caudally (p < 0.001). Method F + P provided more even interfragmentary compression. If method K were used, then combined use with method F + P would be recommended.

Seismic behavior and modeling of T‐shaped reinforced concrete walls under high axial force ratios

AbstractThis paper presents large‐scale quasi‐static tests conducted to investigate the seismic behavior of slender T‐shaped walls under a high axial compression force ratio of approximately 0.19. Four specimens were designed per various codes and design methods for comparison. All specimens failed in a flexural mode, characterized by the crushing of concrete and buckling or fracture of boundary longitudinal rebars at the web toe. The specimens designed per the US code ACI 318‐19 provisions and designed using displacement‐based method exhibited satisfactory deformation capacity with an ultimate drift exceeding 2.0%, which validates the effectiveness of the provisions and displacement‐based method for T‐shaped walls under high axial force ratios. However, the specimen designed per the Chinese code GB 50011‐2010 experienced a sudden drop in strength after 1.0% drift in flange‐in‐tension loading, indicating insufficient design of the special boundary element at the web toe and the necessity of improvement of the current Chinese code provisions. The flexural strength of the T‐shaped wall specimens can be accurately estimated using cross‐sectional analysis. Analysis of the test data indicated that the effective stiffness of the T‐shaped RC walls with an axial force ratio of no greater than 0.1 was significantly lower than 0.35EcIg, while that of the T‐shaped walls with an axial force ratio of 0.19 reached 0.5–0.7EcIg. Existing equations did not provide accurate estimate of the effective stiffness of T‐shaped walls. The lateral drift limit formulation developed by Segura and Wallace could reasonably estimate the lateral drift capacities for the T‐shaped RC wall specimens under high axial force ratios. Finally, three conceptually different models, namely the MVLEM‐3D, SFI‐MVLEM‐3D, and multi‐layer shear element models were adopted for the simulation of T‐shaped RC walls. All three models reasonably predicted the flexural strength capacity (mostly less than 15% error) and the effective stiffness (13%–43% error) of the T‐shaped walls.

Hamstrings vibration reduces tibiofemoral compressive force following anterior cruciate ligament reconstruction.

Individuals who have undergone anterior cruciate ligament reconstruction (ACLR)are at greater risk of developing knee osteoarthritis (OA).This elevated risk of knee OA is associated with high tibiofemoral (TF) compressive force, due to a combination of low knee flexion angles and increased co-contraction of the hamstrings and quadriceps during limb loading. Prolonged vibration of the hamstrings fatigues the intrafusal muscle fibers, which reduces autonomic reflexive excitation of the hamstrings and alleviates reciprocal inhibition to the quadriceps. The aim of this study was to examine the effect of prolonged hamstrings vibration on TF compressive force in individuals who have undergone ACL reconstruction. Fourteen participants with unilateral ACLR and 14 participants without knee injury performed a single-leg drop-land task before and after prolonged (20 min) vibration of the hamstrings. Peak TF compressive force, knee flexion angle, and hamstrings/quadriceps co-contraction were calculated during the deceleration phase of the drop-land task before and after vibration. The ACLR group experienced an 18% decrease in TF compressive force, a 32% increase in knee flexion angle, and a 38% decrease in hamstrings/quadriceps co-contraction after hamstrings vibration. There was no difference in any of the parameters in the noninjured group after vibration. These data suggest that acute prolonged hamstrings vibration has the potential to mitigate TF compressive force, which may protect the knee joint in the long term.Clinical significance: The results of this research are expected to lead to improved clinical care for ACLR patients because it holds promise for mitigating altered joint mechanics and perhaps slowing down the onset of posttraumatic knee osteoarthritis.

Single‐Crystal‐to‐Single‐Crystal Topochemical Synthesis of a Collagen‐inspired Covalent Helical Polymer

AbstractThere is much demand for crystalline covalent helical polymers. Inspired by the helical structure of collagen, we synthesized a covalent helical polymer wherein the repeating dipeptide Gly‐Pro units are connected by triazole linkages. We synthesized an azide and alkyne‐modified dipeptide monomer made up of the repeating amino acid sequence of collagen. In its crystals, the monomer molecules aligned in head‐to‐tail fashion with proximally placed azide and alkyne forming supramolecular helices. At 60 °C, the monomer underwent single‐crystal‐to‐single‐crystal (SCSC) topochemical azide‐alkyne cycloaddition polymerization, yielding a covalent helical polymer as confirmed by single‐crystal X‐ray diffraction (SCXRD) analysis. Compared to the monomer crystals, the polymer single‐crystals were very strong and showed three‐fold increase in Young's modulus, which is higher than collagen, many synthetic polymers and other materials. The crystals of this covalent helical polymer could bear loads as high as 1.5 million times of their own weight without deformation. These crystals could also withstand high compression force and did not disintegrate even at an applied force of 98 kN. Such light‐weight strong materials are in demand for various technological applications.

Single-Crystal-to-Single-Crystal Topochemical Synthesis of a Collagen-inspired Covalent Helical Polymer.

There is much demand for crystalline covalent helical polymers. Inspired by the helical structure of collagen, we synthesized a covalent helical polymer wherein the repeating dipeptide Gly-Pro units are connected by triazole linkages. We synthesized an azide and alkyne-modified dipeptide monomer made up of the repeating amino acid sequence of collagen. In its crystals, the monomer molecules aligned in head-to-tail fashion with proximally placed azide and alkyne forming supramolecular helices. At 60 °C, the monomer underwent single-crystal-to-single-crystal (SCSC) topochemical azide-alkyne cycloaddition polymerization, yielding a covalent helical polymer as confirmed by single-crystal X-ray diffraction (SCXRD) analysis. Compared to the monomer crystals, the polymer single-crystals were very strong and showed three-fold increase in Young's modulus, which is higher than collagen, many synthetic polymers and other materials. The crystals of this covalent helical polymer could bear loads as high as 1.5 million times of their own weight without deformation. These crystals could also withstand high compression force and did not disintegrate even at an applied force of 98 kN. Such light-weight strong materials are in demand for various technological applications.

Knee kinematics are primarily determined by implant alignment but knee kinetics are mainly influenced by muscle coordination strategy

Implant malalignment has been reported to be a primary reason for revision total knee arthroplasty (TKA). In addition, altered muscle coordination patterns are commonly observed in TKA patients, which is thought to alter knee contact loads. A comprehensive understanding of the influence of surgical implantation and muscle recruitment strategies on joint contact mechanics is crucial to improve surgical techniques, increase implant longevity, and inform rehabilitation protocols. In this study, a detailed musculoskeletal model with a 12 degrees of freedom knee was developed to represent a TKA subject from the CAMS-Knee datasets. Using motion capture and ground reaction force data, a level walking cycle was simulated and the joint movement and loading patterns were estimated using a novel technique for concurrent optimization of muscle activations and joint kinematics. In addition, over 12′000 Monte Carlo simulations were performed to predict knee contact mechanics during walking, considering numerous combinations of implant alignment and muscle activation scenarios. Validation of our baseline simulation showed good agreement between the model kinematics and loading patterns against the in vivo data. Our analyses reveal a considerable impact of implant alignment on the joint kinematics, while variation in muscle activation strategies mainly affects knee contact loading. Moreover, our results indicate that high knee compressive forces do not necessarily originate from extreme kinematics and vice versa. This study provides an improved understanding of the complex inter-relationships between loading and movement patterns resulting from different surgical implantation and muscle coordination strategies and presents a validated framework towards population-based modelling in TKA.

Effect of low-intensity resistance training with blood flow restriction on functional status in knee osteoarthritis

Background: Knee osteoarthritis is a joint pathology with high prevalence, resulting from the increase of aging and obesity in the world population. Articular cartilage destruction can cause pain and eventually reduces activities of daily living and affects functional status in subjects with knee osteoarthritis. Exercise interventions in knee-OA aimed at increasing knee extensor muscle strength involve high-intensity resistance training but may result in joint pain due to high-compressive forces. Other alternative method includes low-intensity resistance training performed with blood flow restriction, a potential intervention for a patient who does not tolerate high loads due to lower mechanical stress. This study aims to determine the effects of blood flow restriction with low-intensity resistance training on the quadriceps for six weeks on functional status in knee-OA patients. Methods: Twenty-eight patients aged 50-70 years old with knee-OA in Physical Medicine and Rehabilitation Outpatient Clinic Soetomo Hospital Surabaya were randomized into control and treatment groups. Both groups underwent a 6-week supervised training program consisting of LI-RT (30% 1-RM) two sessions/week. The treatment group received an additional application of blood flow restriction using a cuff on 1/3 of the upper thigh with 50 mmHg occlusion pressure. Both groups were assessed for functional status by self-reported WOMAC questionnaire before and after the protocol. Results: Both training methods were able to reduce WOMAC pain and improve physical function subscales significantly, but WOMAC stiffness subscales only reduced significantly in low-intensity resistance training with blood flow restriction. There were no significant differences between groups for any domain from WOMAC, nor any significant differences between delta scores (all P &gt; 0.05). Conclusion: Low-intensity resistance training with and without blood flow restriction was similarly effective in enhancing functional status in subjects with knee osteoarthritis.

Auxetic Behaviour of Rigid Connected Squares.

The paper presents an analysis of rotating rigid unit (RRU) auxetic structures, the special property of which is negative Poisson's ratio. The crucial features of such modified structures are the well-functioning linkages of the square units at their pivot points. This ensures the stable functioning of such structures in tension or compression. The presented geometrical analysis of these auxetic structures may facilitate their adequate construction and allow one to determine the expected values of their expansion as well as the desired porosity. The results are confirmed based on the behaviour of physical models produced by the assembly of square units. The change in the dimensions of the physical models when moving from a closed to an open position is consistent with the predictions of the geometric models. By modifying the well-known 'rotating squares' model, physical structures with auxetic properties are obtained that can be utilised in industrial conditions, where a simultaneous change of linear dimensions is needed-either in compression or in tension. The assembly method may prove efficient in building such structures, given the abilities of assembly robots to regularly arrange the unit cells in lines and rows and to connect them with rings at the designated positions (evenly spaced perforations). The presented auxetic structures might find their potential application in, e.g., expansion joints or structures in which the porosity is mechanically changed, such as mesoscale structures. The tested structures subjected to high compressive forces buckle when the yield strength of the rigid unit material is exceeded.

Reinforcement determination for anchorage zones of post-tensioned concrete beams

In post-tensioned concrete beams, the high concentrated compressive forces are transmitted to the concrete zones at the beam ends through the anchorage devices. As a result, they can burst and split if the concrete is not adequately reinforced. The paper determines the reinforcement in anchorage zones with axially loaded post-tensioned tendons using the linear elastic analysis method, which involves computing the state of stresses as linearly elastic, and the equilibrium-based plasticity approach method as strut-and-tie models to provide prestressing force paths as a truss structure. Some numerical models are also analyzed to clarify the present methods.

Finite element analysis of lattice designed lumbar interbody cage based on the additive manufacturing.

Additive manufacturing (AM) methods, which facilitate the production of complex structures with different geometries, have been used in producing interbody cages in recent years. In this study, the effects of Ti6Al4V alloy interbody lattice designed fusion cages between the third and fourth lumbar vertebrae where degenerative disc diseases occur were investigated using the finite element method. Face centered cubic (FCC), body centered cubic (BCC), and diamond structures were selected as the lattice structure suitable for the interbody cage. A kidney shaped interbody lumbar cage was designed. The designated lattice structures were selected by adjusting the cell sizes suitable for the designed geometry, and the mesh configuration was made by the lumbar lattice structure. 400 N Axial force and 7.5 N.m moments were applied to the spine according to lateral bending, flexion, and torsion. 400 N axial force and 7.5 N.m flexion moment is shown high strain and total deformation then lateral bending and torsion on BCC FCC and diamond lattice structured interbody cages. In addition, the effects of lattice structures under high compression forces were investigated by applying 1000 N force to the lattice structures. When von Mises stresses were examined, lower von Mises stress and strains were observed in the BCC structure. However, a lower total deformation was observed in the FCC. Due to the design of the BCC and the diamond structure, it is assumed that bone implant adhesion will increase. In the finite element analysis (FEA), the best results were shown in BCC structures.

The mechanical loading of the spine in physical activities

PurposeTo summarize the mechanical loading of the spine in different activities of daily living and sports.MethodsSince the direct measurement is not feasible in sports activities, a mathematical model was applied to quantify spinal loading of more than 600 physical tasks in more than 200 athletes from several sports disciplines. The outcome is compression and torque (normalized to body weight/mass) at L4/L5.ResultsThe data demonstrate high compressive forces on the lumbar spine in sport-related activities, which are much higher than forces reported in normal daily activities and work tasks. Especially ballistic jumping and landing skills yield high estimated compression at L4/L5 of more than ten times body weight. Jumping, landing, heavy lifting and weight training in sports demonstrate compression forces significantly higher than guideline recommendations for working tasks.ConclusionThese results may help to identify acute and long-term risks of low back pain and, thus, may guide the development of preventive interventions for low back pain or injury in athletes.

Influence of Deposition Temperature and Compaction Force on the Infusion Properties of DFP Preforms

The deposition of dry fiber materials in the dry fiber placement (DFP) process with subsequent impregnation is becoming increasingly widespread. The wing covers of the Irkut MS 21 are already being manufactured using the DFP process, and research projects at major aircraft manufacturers are increasingly incorporating the technology. In this process, the deposition speed depends on the temperature and the compaction force. However, it is not only the laying speed that counts during production, but also the impregnation afterwards. Thus, the effects of the depositing parameters on the infusion properties must be known. In this study, a two-step approach is used. Planar preforms (Hexcel HiTape) that have been deposited with different parameters are divided into four quadrants, and first samples are analyzed for isotropic properties in a two-dimensional infusion test. Then, one-dimensional infusion tests are performed so that infusion times can be compared. The tests show that the lowest infusion time can be obtained at low deposition temperature and high compression force. Additionally, using a comparable material (Solvay TX 1100), it is shown that increasing the gaps between the tows increases the permeability and homogeneity of the preform.

Huanglongbing disease symptoms and the postharvest quality of ‘LB8-9’ (Sugar Belle®) and ‘Tango’ mandarins as affected by ethylene treatment

Sustainability of Florida citrus industry has become the biggest concern for growers due to widespread of Huanglongbing (HLB) in almost 100% of Florida orchards with no cure in sight. Some mandarin varieties, ‘LB8-9’ (Sugar Belle) and ‘Tango’, are tolerant against HLB as compared to sweet oranges and grapefruit cultivars. Mandarins are a fresh market produce, so uniform and attractive peel color must align with consumer expectations. Florida’s subtropical weather inhibits peel chlorophyll breakdown and the presence of HLB further exacerbates peel color development. To improve peel color and quality (thus marketability of fruit) of Florida grown mandarins, a study was conducted to evaluate how HLB symptomatic (S) and asymptomatic (AS) Sugar Belle and ‘Tango’ mandarin fruit respond to degreening treatment (5 µL L−1 ethylene at 25 °C and 85-90% relative humidity, for 72 or 96 h, respectively). Degreened and control fruit were stored at 24±1 °C and 80-85% relative humidity for 14 d with weekly evaluations. With degreening, fruit (AS and S) of Sugar Belle and ‘Tango’ attained lower peel hues and higher chroma (more orange and pure color) compared to untreated control, in a cultivar dependent manner. In both cultivars, S fruit retained higher peel hues (less orange) than AS fruit at harvest and during storage. S fruit also had reduced fruit size, weight, and peel thickness compared to AS fruit. At harvest, S fruit of both cultivars had higher compression forces, peel puncture resistance forces, sugars (glucose and sucrose), and citric acid than AS fruit. During storage, S fruit retained higher citric acid than AS fruit in both cultivars. With degreening, AS and S fruit from both cultivars had lower citric acid than non-treated control during storage. Upon sensory quality evaluation of Sugar Belle, lower sourness scores were recorded for degreened Sugar Belle fruit compared to untreated control irrespective of HLB fruit symptoms. Overall, degreening treatment enhanced peel color development without accelerating storage decay incidence or deteriorating fruit quality. This suggests that degreening treatment can be a potent industry tool for achieving marketable fruit peel color from HLB-affected mandarin trees grown in subtropical climates without altering the flavor of the fruit.