Increase In Cross-sectional Area Research Articles

Dietary Supplementation with Nano-Curcumin Improves the Meat Quality and Nutrition Value of Largemouth Bass (Micropterus salmoides) Fed with a High-Carbohydrate Diet

This study investigated the effects of curcumin nanoparticles on the flesh quality of largemouth bass on a high-carbohydrate diet. A total of 180 fish (11.01 ± 0.02 g) were fed three semi-purified diets: the Control group (LC) were supplemented with standard carbohydrate (10%), the experimental group (HC) were supplemented with 15% carbohydrate, and the experimental group were supplemented with 0.2% nano-curcumin added to 15% carbohydrate (HCN) for 6 weeks. Results showed that a* value, taurine, valine, isoleucine, histidine, cystine, fatty acids (C17:0 and C20:2n6), MDA (malondialdehyde) content, and SOD (Superoxide dismutase) activity were significantly elevated (p < 0.05) in HC. Muscle fibers showed significant increases in horizontal diameter, longitudinal diameter, and cross-sectional area (p < 0.05), as well as up-regulated expression levels of the MRFS (myogenic regulatory factor) family gene and MSTN (myostatin) (p < 0.05), and a significant decrease in C16:1n7 in HC (p < 0.05). Importantly, the HCN group enhanced the muscle quality of largemouth bass by elevating the L* value, valine, isoleucine, arginine and cystine, C20:2n6, decreasing (p < 0.05) refrigeration loss, chewability, firmness and hardness, then MDA content and SOD activity, and downregulating (p < 0.05) MSTN and MRFS family gene expression levels to improve largemouth bass muscle quality.

Impact of Eccentric Exercise Interventions with Small and Large Ranges of Motion on Rat Skeletal Muscle Tissue and Muscle Force Production.

Eccentric training induces greater hypertrophy while causing more muscle damage than concentric training. This study examined the effects of small-range eccentric contractions (SR-ECCs) and large-range eccentric contractions (LR-ECCs) on muscle morphology, contractility, and damage in rats. Thirty male Fischer 344 rats were divided into five groups: small-range ECC single-bout (SR-ECCSB, n = 4), large-range ECC single-bout (LR-ECCSB, n = 4), SR-ECC intervention (SR-ECCIntv, n = 7), LR-ECC intervention (LR-ECCIntv, n = 8), and control (Cont, n = 7). These groups underwent transcutaneous electrical stimulation involving 80 ECCs twice a week for four weeks. The results indicated that the LR-ECCSB group had more Evans blue dye-positive fibers than other groups. The SR-ECCIntv group showed no increase in the mean myofiber cross-sectional area. However, Pax7+ and Ki67+ cells significantly increased in both ECCIntv groups compared to the Cont group, and the connective tissue area was significantly greater in the LR-ECCIntv than in others. Muscle force was lower in both ECCIntv groups compared to the Cont group. These findings suggest that SR-ECC intervention may induce a smaller increase in the number of fibers with a large myofiber cross-sectional area and satellite cell proliferation with less muscle damage and myofibrosis compared to LR-ECCs.

Polycaprolactone-based shape memory foams as self-fitting vaginal stents

There is an urgent critical need for a patient-forward vaginal stent that can prevent debilitating vaginal stenosis that occurs after pelvic radiation treatments and vaginal reconstruction. To this end, we developed a self-fitting vaginal stent based on a shape-memory polymer (SMP) foam that can assume a secondary, compressed shape for ease of deployment. Upon insertion, the change in temperature and hydration initiates foam expansion to shape fit to the individual patient and restore the lumen of the stent to allow egress of vaginal secretions. To achieve rapid actuation at physiological temperature, we investigated the effect of architecture of two photocurable, polycaprolactone (PCL) macromers. Star-PCL-tetraacrylate displayed a reduced melting temperature as compared to a linear-PCL-diacrylate. Upon fabrication into high porosity foams with emulsion-templating, both compositions displayed shape fixity (>90 %) in a crimped, temporary shape. However, only the PCL star-foams displayed shape recovery (∼84 %) at 37 °C with expansion back to its permanent shape. A custom mold and curing system were then used to fabricate the PCL star-foams into hollow, cylindrical stents. The stent was crimped to its temporary insertion shape (50 % reduction in diameter, OD ∼ 11 mm) with a custom radial crimper and displayed excellent shape fixity for deployment (> 95 %) and shape recovery (∼ 100 %). To screen vaginal stents, we developed a custom benchtop pelvic model that simulated vaginal anatomy, temperatures, and pressures with an associated computational model. The crimped SMP vaginal stent was deployed in the model and expanded to walls of the canal (∼70 % increase in cross-sectional area) in less than 5 min after irrigation with warm water. The vaginal stent demonstrated retention of vaginal caliber with less than 10 % decrease in cross-sectional area under physiological pressures. Collectively, this work demonstrates the potential for SMP foams as self-fitting vaginal stents to prevent stenosis and provides new open-source tools for the iterative design of other gynecological devices. Statement of significanceVaginal stenosis, a painful narrowing of the vaginal canal, is a common complication after pelvic radiation therapy or reconstructive surgery. To address this clinical need, we have created a self-fitting vaginal stent from a shape-memory polymer foam. The stent compresses for easy insertion and then expands to adapt to each patient's anatomy to maintain an open vaginal canal and prevent stenosis. This innovative stent provides a patient-friendly solution that could make a significant difference for women undergoing pelvic treatments by reducing pain, aiding recovery, and improving quality of life.

Local buckling behavior and reinforced mechanisms of short circular timber columns confined with bamboo scrimber

Developing sustainable high-performance bamboo scrimber (BS) as structural and reinforcing materials is significant. BS was used as reinforcing material to increase ancient timber columns' load-bearing capacity and safety via a damage-free strengthening method. The BS panels were fastened to the surface of the wooden columns by spaced steel strips. The spacing of the steel strips was the important factor in balancing the appearance of the confined reinforced timber columns with maximizing the strength of the confined panels. In this study, eight short circular wooden columns reinforced with BS with varying spacing of steel strips were fabricated and tested under axial compression. Each specimen's damage characteristics, load-carrying capacity performance, and strain coordination were analyzed and compared. The reinforcement method has a significant effect, and the reinforcement system of all specimens provides an additional load-bearing capacity of more than 48.3 % with about 38 % increase in cross-section area. The load-bearing capacity decreases significantly with increasing the spacing of steel strips. When the steel strips' distance is more than 363 mm (the corresponding slenderness ratio is 41), the confined panel showed significant buckling behavior from the beginning of loading. In contrast, the confined panels of the other circular reinforced timber column showed buckling and load drop only near the peak load, which takes full advantage of the strength of the BS material. The strain growth trends of the confined panels and core column were similar, although the strain of the confined panels' bending offsets some of the compressive strain, which was evidence that they were synergistically stressed under axial compression. The part of confined slats between the steel strips was intercepted as a compression bar, and the commonly used equation for the load-bearing capacity of a flexible bar was introduced. Various flex rod equations based on material properties were calculated and compared to the test results. The calculations showed that the buckling equation suggested by Euler and CSA086-19 had the best agreement with BS materials with similar proportional limits and ultimate strength. BS as a flex rod was suggested with a slenderness ratio not exceeding 32, and a general equation for calculating the steel strip spacing considering the material thickness was proposed for construction reference.

Poster 214: Cross Sectional Area of Hip Muscles Before and After Surgery for Femoroacetabular Impingement

Objectives: Femoroacetabular impingement (FAI) syndrome is a common cause of hip pain and surgery is a treatment option for patients who do not respond to conservative treatment. Previous studies have identified increases in postoperative hip muscle volume and cross-sectional area (CSA) as associated with increases in patient reported outcomes following hip surgery. There has been a lack of literature analyzing the change of hip muscle cross sectional CSA on MRI following arthroscopic hip surgery for FAI and the effect of changes in hip muscle CSA on patient reported outcomes following surgery. The purpose of this study is to analyze the change in hip muscle cross sectional area (CSA) after arthroscopic surgery for FAI syndrome. Methods: This is a single center, single surgeon, retrospective analysis performed between August 2007 and May 2023. All patients who had a pre-operative MRI within 1 year of their date of surgery and at least one postoperative MRI were included in the study. Cross sectional areas were measured by one blinded researcher and results were checked for reliability by a musculoskeletal radiologist. Statistical analysis was completed using SPSS, Version 24 and normally distributed continuous variables between cohorts were compared using the two-sample Student t test. Results: Initially 1390 patients were included in the study but only 95 were found to have a preoperative hip MRI within 1 year of their date of surgery as well as a postoperative MRI. The average age of the cohort was 35.8 ± 15.7, the cohort was 33.7% male and 66.3% female, and had an average BMI of 23.3 ± 8.1. The mean time between surgery and postoperative MRI was 14.8 ± 8.3 months. There was a significant difference between preoperative and postoperative hip muscle CSA for gluteus maximus (4298.6±883.6 mm2 vs. 4384.6±967.6 mm2, p<0.01), gluteus minimus (1037.0±199.2 mm2 vs. 1074.9±202.3 mm2, p<0.001), and pectineus (415.7±121.9 mm2 vs. 426.7±106.3 mm2, p=0.04). There were no other significant differences between preoperative and postoperative hip muscle CSA values between the other muscles analyzed. A linear regression found that an increase in the change in CSA of the gluteus maximus significantly predicted an increase in mHHS at 1 year (β=3.103, p=0.046) when controlling for age, sex, BMI and time from surgery to postoperative MRI. A linear regression found that an increase in the change in cross sectional area of the pectineus significantly predicted an increase in NAHS at 1 year when controlling for age, sex, BMI and time from surgery to post-op MRI (β=0.186, p=0.037). Conclusions: Patients who undergo surgery for FAI have significantly increased gluteus maximus, gluteus minimus and pectineus muscle CSA on post-operative MRIs. Furthermore, increases in both gluteus maximus and pectineus muscle CSA was found to be significantly associated with increases in mHHS and NAHS at 1 year follow up respectively.

Investigating the impact of cross-sectional area on the crushing characteristics of axially-loaded hemispherical composite shells

The research focus has shifted towards lightweight structures with high energy absorption capabilities due to advancements in automotive safety technology. This study specifically investigates the impact of cross-sectional area on the energy absorption characteristics of hemispherical composite shells. The experimental phase involves characterizing a glass fiber epoxy composite, followed by the manufacture of hemispherical composite shell specimens with varying cross-sectional areas. These specimens undergo quasi-static axial compressive loading, and the energy absorption parameters are analyzed. The results indicate a significant influence of the composite cross-sectional area on the crushing behavior of hemispherical shells, with a observed decrease in specific energy absorption as the cross-sectional area increases. Additionally, a 3D Finite Element (FE) model is created using ABAQUS FE code to numerically simulate the crushing process. The model’s predictions are compared and validated against experimentally measured values, demonstrating a satisfactory correlation.

Determination of muscle shape deformations of the tibialis anterior during dynamic contractions using 3D ultrasound.

In this paper, we introduce a novel method for determining 3D deformations of the human tibialis anterior (TA) muscle during dynamic movements using 3D ultrasound. An existing automated 3D ultrasound system is used for data acquisition, which consists of three moveable axes, along which the probe can move. While the subjects perform continuous plantar- and dorsiflexion movements in two different controlled velocities, the ultrasound probe sweeps cyclically from the ankle to the knee along the anterior shin. The ankle joint angle can be determined using reflective motion capture markers. Since we considered the movement direction of the foot, i.e., active or passive TA, four conditions occur: slow active, slow passive, fast active, fast passive. By employing an algorithm which defines ankle joint angle intervals, i.e., intervals of range of motion (ROM), 3D images of the volumes during movement can be reconstructed. We found constant muscle volumes between different muscle lengths, i.e., ROM intervals. The results show an increase in mean cross-sectional area (CSA) for TA muscle shortening. Furthermore, a shift in maximum CSA towards the proximal side of the muscle could be observed for muscle shortening. We found significantly different maximum CSA values between the fast active and all other conditions, which might be caused by higher muscle activation due to the faster velocity. In summary, we present a method for determining muscle volume deformation during dynamic contraction using ultrasound, which will enable future empirical studies and 3D computational models of skeletal muscles.

The effects of exercise and mitochondrial transplantation alone or in combination against Doxorubicin-induced skeletal muscle atrophy.

Doxorubicin (DOX) is a chemotherapy drug used to treat various types of cancer, but it is associated with significant side effects such as skeletal muscle atrophy. Exercise has been found to prevent skeletal muscle atrophy through the modulation of mitochondrial pathways. Mitochondrial transplantation (MT) may mitigate toxicity, neurological disorders, kidney and liver injury, and skeletal muscle atrophy. The objective of this study was to evaluate the effects of MT, exercise, and MT with exercise on DOX-induced skeletal muscle atrophy. Male Sprague Dawley rats were randomly assigned to the following groups: control, DOX, MT with DOX, exercise with DOX, and exercise with MT and DOX. A 10-day treadmill running exercise and MT (6.5µg/100 µL) to tibialis anterior (TA) muscle were administered prior to a single injection of DOX (20mg/kg). Our data showed that exercise and MT with exercise led to an increase in cross-sectional area of the TA muscle. Exercise, MT and MT with exercise reduced inflammation and maintained mitochondrial enzyme activity. Additionally, exercise and MT have been shown to regulate mitochondrial fusion/fission. Our findings revealed that exercise and MT with exercise prevented oxidative damage. Furthermore, MT and MT with exercise decreased apoptosis and MT with exercise triggered mitochondrial biogenesis. These findings demonstrate the importance of exercise in the prevention of skeletal muscle atrophy and emphasize the significant benefits of MT with exercise. To the best of our knowledge, this is the first study to demonstrate the therapeutic effects of MT with exercise in DOX-induced skeletal muscle atrophy.

Research on the theory and method of reduced-hole blasting for large cross-section tunnel based on explosive energy dissipation

The traditional tunnel drilling and blasting method places cut holes at the lower center of the excavation face, resulting in an excessive number of blasting holes. With the continuous increase in cross-section area, this design concept can no longer meet the requirements of safe and efficient tunnel boring for large cross-section tunnels. This paper puts forward the theory and method of reduced-hole blasting for large cross-section tunnels, as an alternative to the traditional drilling and blasting method of the “more holes, less charge” design concept. Based on the explosion energy dissipation law and rock’s critical crushing energy dissipation characteristics, the calculation method of the extrapolation distance of the wedge-cut holes is given. The optimum extrapolation distance of the wedge-cut holes was verified using numerical simulation and field tests. The results show that the number of drilling holes can be reduced by about 15.8% using the theory and method proposed in this paper, and at the same time, the damage of retained rock can be effectively controlled. The results of this study can provide a reference for the design of blast network parameters for similar large cross-section tunnels.

Performance analysis of pulse detonation ramjet

Abstract A Pulse Detonation Ramjet (PDR) performance evaluation model is established based on the component-based method. The influence law of working parameters of pulse detonation combustor (PDC), PDR geometry parameters, flight speed and altitude on the performance is analyzed. Results are as follows. (1) With the increase of the equivalent ratio, the PDR specific thrust first increases and then decreases, reaching a maximum value around 1.2, but the fuel specific impulse always decreases; (2) The change of inlet throat cross-sectional area has little effect on specific thrust and fuel specific impulse, but the increase of nozzle throat cross-sectional area will have a negative effect; (3) PDR specific thrust and fuel specific impulse increase first and then decrease with the increase of flight Mach number and altitude; (4) Compared with a ramjet engine, the advantage range of PDR can reach 18.04 %, but gradually decreases with the increase of Mach number.

Synergistic Therapy for Graves’ Ophthalmopathy-Associated Eyelid Retraction: Steroid, 5-FU, and Botulinum Neurotoxin a Combination

Background: Graves’ ophthalmopathy (GO) is characterized by upper eyelid retraction (UER), the most prevalent clinical sign. We aimed to assess the clinical efficacy of a multimodal combination of steroids, 5-fluorouracil (5-FU), and botulinum neurotoxin A (BoNT-A) injections in managing UER with GO and analyze the clinical factors in relation to the injection response. Methods: A total of 37 eyes from 23 patients were enrolled for UER with GO. At the endocrinology clinic, the patients were referred to the ophthalmology clinic after taking antithyroid medication for an average of 5.76 months (13 patients), while 10 patients were initially diagnosed with GO and referred to the endocrinology clinic for management of the thyroid hormone function. They performed an orbital computed tomography (CT) scan and measured the cross-sectional area of the orbit, orbital fat, and each extra ocular muscle (EOM) except for the inferior oblique muscle 4 mm behind the eyeball. Each of the EOMs and orbital fat were calculated as a ratio to the total orbit area. A total of 0.1 cc of triamcinolone (40 mg/mL), dexamethasone (5 mg/mL), 5-FU, and BoNT-A (2.5 units) was injected transconjunctivally. Medical records were examined and photographs were utilized to assess MRD1, inferior palpebral fissure (IPF), and lid lag during down gaze before and after the injection. The patients were divided into two groups: responders (more than 1 mm decrease in MRD1 after injection) and non-responders. During the follow-up period (11.0 ± 11.6 months), any potential adverse effects were monitored. Results: CAS decreased from 3.0 ± 0.8 to 1.4 ± 0.5 after the injection, and MRD1 decreased from 5.0 ± 0.9 mm to 4.5 ± 1.3 mm. Sixty percent of the patients were responders. Before and after the injection, the difference between IPF and MRD1 in responders was 0.60 ± 1.10 mm and 0.90 ± 0.90 mm, respectively, whereas, in non-responders, it was −0.57 ± 0.88 mm and −0.15 ± 0.75 mm, respectively. In the responders, pre-injection IPF and FT4 were significantly higher (p < 0.05). Responders had a larger EOM cross-sectional area (153.5 ± 18.0 mm2), including a larger lateral rectus muscle cross-sectional area (37.6 ± 9.7 mm2) than non-responders (132.0 ± 27.9 mm2; 29.1 ± 8.1 mm2). In responders, the treatment effect on IPF and MRD1 remained consistent at 1.2 ± 3.4 mm and 1.2 ± 1.6 mm, respectively, during the latest follow-up assessment. Conclusions: The combination injection of corticosteroids, 5-FU, and BoNT-A would be effective, especially, in patients with hyperthyroidism and an elongated IPF. Additionally, an increase in EOM cross-sectional area on CT, up to 150 mm2, may serve as an additional positive indicator for the use of multimodal injections in UER with GO.

Functional evaluation of Septal L-strut extension graft in East Asians

BackgroundThe septal L-strut extension graft (SLEG) consists of anterior extended spreader graft and caudal septal extension graft. SLEG is used to increase the anterocaudal projection from a low-profile nose by creating the de-novo septum. This retrospective study verified the effectiveness of SLEG in improving the nasal function in East Asians. MaterialsMedical records of patients who underwent septorhinoplasty with SLEG were retrospectively reviewed. The clinical features showed under-projected lower two-thirds of the nose with septal deviation, saddle nose, and short nose. We analyzed the post-operative changes in the NOSE score and variables of nasal geometry measured using acoustic rhinometry through long-term follow-up. ResultsPatients were divided into two groups, those who underwent SLEG with turbinoplasty (Group A) and SLEG alone (group B). The NOSE scores decreased significantly in groups A and B, and the improvement was statistically more significant in Group A (p < 0.05). Acoustic rhinometry showed an increase in nasal cavity volume (VOL1) on the deviated side in Group A, and an increase in minimal cross-sectional area 1 (MCA1) on the deviated side in Group B (p < 0.05). The non-deviated side did not show significant reduction in MCA1 and VOL1 after SLEG with or without turbinoplasty. Thus, SLEG, by itself, improved airway function in East Asians. ConclusionsSLEG has proven to be valuable in improving nasal function.

Biomechanical analysis of tendon turnover tenorrhaphy compared to direct repair and Pulvertaft weave.

The aim of the present study was to evaluate biomechanical properties of tendon turnover repair in comparison to direct repair and Pulvertaft weave. A total of 48 sheep flexor tendons were assigned to eight groups comprising single or double tendon turnover repair, tendon turnover segment (without tenorrhaphy), direct repair or Pulvertaft weave. Tensile strength, stiffness and failure mechanisms were evaluated with a 500 N load cell. Turnover repair showed no significant difference in tensile strength to direct repair. Failure in turnover repair occurred largely at the site of tenorrhaphy due to suture pull-through or suture rupture. the increase in cross-sectional area after turnover repair was similar to that after direct repair, but less than after Pulvertaft weave. Tendon turnover offers tensile strength similar to direct repair with no associated increase in bulk. It provides a biomechanically secure and quicker alternative to tendon grafting for reconstructing tendon defects, without secondary donor site morbidity.Level of evidence: V.

A novel imaging method (FIM-ID) reveals that myofibrillogenesis plays a major role in the mechanically induced growth of skeletal muscle

An increase in mechanical loading, such as that which occurs during resistance exercise, induces radial growth of muscle fibers (i.e. an increase in cross-sectional area). Muscle fibers are largely composed of myofibrils, but whether radial growth is mediated by an increase in the size of the myofibrils (i.e. myofibril hypertrophy) and/or the number of myofibrils (i.e. myofibrillogenesis) is not known. Electron microscopy (EM) can provide images with the level of resolution that is needed to address this question, but the acquisition and subsequent analysis of EM images is a time- and cost-intensive process. To overcome this, we developed a novel method for visualizing myofibrils with a standard fluorescence microscope (fluorescence imaging of myofibrils with image deconvolution [FIM-ID]). Images from FIM-ID have a high degree of resolution and contrast, and these properties enabled us to develop pipelines for automated measurements of myofibril size and number. After extensively validating the automated measurements, we used both mouse and human models of increased mechanical loading to discover that the radial growth of muscle fibers is largely mediated by myofibrillogenesis. Collectively, the outcomes of this study offer insight into a fundamentally important topic in the field of muscle growth and provide future investigators with a time- and cost-effective means to study it.

A novel imaging method (FIM-ID) reveals that myofibrillogenesis plays a major role in the mechanically induced growth of skeletal muscle.

An increase in mechanical loading, such as that which occurs during resistance exercise, induces radial growth of muscle fibers (i.e. an increase in cross-sectional area). Muscle fibers are largely composed of myofibrils, but whether radial growth is mediated by an increase in the size of the myofibrils (i.e. myofibril hypertrophy) and/or the number of myofibrils (i.e. myofibrillogenesis) is not known. Electron microscopy (EM) can provide images with the level of resolution that is needed to address this question, but the acquisition and subsequent analysis of EM images is a time- and cost-intensive process. To overcome this, we developed a novel method for visualizing myofibrils with a standard fluorescence microscope (fluorescence imaging of myofibrils with image deconvolution [FIM-ID]). Images from FIM-ID have a high degree of resolution and contrast, and these properties enabled us to develop pipelines for automated measurements of myofibril size and number. After extensively validating the automated measurements, we used both mouse and human models of increased mechanical loading to discover that the radial growth of muscle fibers is largely mediated by myofibrillogenesis. Collectively, the outcomes of this study offer insight into a fundamentally important topic in the field of muscle growth and provide future investigators with a time- and cost-effective means to study it.

Identification of key differentially methylated genes in regulating muscle development and intramuscular fat deposition in chickens

Muscle development and intramuscular fat (IMF) deposition are intricate physiological processes characterized by multiple gene expressions and interactions. In this research, the phenotypic variations in the breast muscle of Jingyuan chickens were examined at three different time points: 42, 126, and 180 days old. Differential expression analysis and weighted gene co-expression network analysis (WGCNA) were performed to identify differentially methylated genes (DMGs) responsible for regulating muscle development and IMF deposition. The findings indicate a significant increase in breast muscle weight (BMW), myofiber diameter, and cross-sectional area, as well as IMF content, in correlation with the progressive number of growing days in Jingyuan chickens. The findings also revealed that 380 hypo-methylated and 253 hyper-methylated DMGs were identified between the three groups of breast muscle. Module gene and DMG association analysis identified m6A methylation-mediated multiple DMGs associated with muscle development and fat metabolism. In vitro cell modeling analysis reveals stage-specific differences in the expression of CUBN, MEGF10, BOP1, and BMPR2 during the differentiation of myoblasts and intramuscular preadipocytes. Cycloleucine treatment significantly inhibited the expression levels of CUBN, BOP1, and BMPR2, and promoted the expression of MEGF10. These results suggest that m6A methylation-mediated CUBN, MEGF10, BOP1, and BMPR2 can serve as potential candidate genes for regulating muscle development and IMF deposition, and provide an important theoretical basis for further investigation of the functional mechanism of m6A modification involved in adipogenesis.

Model test on failure mechanisms of deep high-stress soft rock roadways based on excavation compensation method

Traditional support (TS) is not sufficient to address the issue of large deformations in deep soft rock roadways with high stress. Based on model tests, this study considered the superposition effects of the evolution of tangential stress σ1 and radial stress σ3 on the crack propagation of excavated rock mass. Moreover, it explored the response characteristics and failure mechanisms of surrounding rock under different support modes. The results showed that, compared with the TS, the compensation support (CS) reduces the surrounding rock deformation, fracture and expansion area, and crack length by 73.7, 86.5, and 37.7%, respectively, while the roadway cross-sectional area increases by 36.8%. At 0.5R, σ3 of the shallow surrounding rock increases by 68.3%, and the peak value of σ1 at this location drops by 18.2%. The excavation effect causes σ3 and σ1 of the surrounding rock to decrease and increase, respectively. The decrease in σ3 leads to initiation of microcracks in the shallow surrounding rock, whereas the increase in σ1 causes the cracks to further open and propagate deeper. Finally, the dislocation, slippage and overturning of the fractured rock blocks along the structural planes result in bulking deformation of the shallow surrounding rock. The occurrence of microcracks in the deep surrounding rock leads to dilatation deformation. The CS strongly compensates for the stress of surrounding rock through negative Poisson’s ratio (NPR) cables, giving full play to the triaxial strength of the surrounding rock and mobilising the self-bearing capacity of the deep rock mass, thereby inhibiting the propagation and penetration of cracks. In contrast, the TS cables have a low prestress and weak excavation compensation effect, which makes it difficult to inhibit the evolution and coalescence of cracks, leading to large deformations in the surrounding rock.

Experimental Evaluation of the Effects of Discrete-Grading-Induced Discontinuities on the Material Properties of Functionally Graded Ti-6Al-4V Lattices.

In this study, we compared the material properties of linearly and sharply graded Ti6Al4V additively manufactured samples to investigate whether the more severe discontinuities caused by sharp grading can reduce performance. We performed compression testing with digital image correlation (DIC) in two loading directions for each grading design to simulate iso-stress and iso-strain conditions. We extracted the elastic stiffness, yield strength, yield strain, and energy absorption capacity of each sample. In addition, we used micro-computed tomography (micro-CT) imaging to examine the printing quality and dimensional accuracy. We found that sharply graded struts have a 12.95% increase in strut cross-sectional areas, whereas linearly graded struts produced an average of 49.24% increase compared to design. However, sharply graded and linearly graded FGL samples do not have statistically significant differences in elastic stiffness and yield strength. For the iso-strain condition, the average DIC-corrected stiffnesses for linearly and sharply graded samples were 6.15 GPa and 5.43 GPa, respectively (p = 0.4466), and the yield stresses were 290.4 MPa and 291.2 MPa, respectively (p = 0.5734). Furthermore, we confirmed different types of printing defects using micro-CT, including defective pores and disconnected struts. These results suggest that the loss of material properties caused by manufacturing defects outweighs the adverse effects of discrete-grading-induced discontinuities.

A novel computational framework for the estimation of internal musculoskeletal loading and muscle adaptation in hypogravity.

Introduction: Spaceflight is associated with substantial and variable musculoskeletal (MSK) adaptations. Characterisation of muscle and joint loading profiles can provide key information to better align exercise prescription to astronaut MSK adaptations upon return-to-Earth. A case-study is presented of single-leg hopping in hypogravity to demonstrate the additional benefit computational MSK modelling has when estimating lower-limb MSK loading. Methods: A single male participant performed single-leg vertical hopping whilst attached to a body weight support system to replicate five gravity conditions (0.17, 0.25, 0.37, 0.50, 1 g). Experimental joint kinematics, joint kinetics and ground reaction forces were tracked in a data-tracking direct collocation simulation framework. Ground reaction forces, sagittal plane hip, knee and ankle net joint moments, quadriceps muscle forces (Rectus Femoris and three Vasti muscles), and hip, knee and ankle joint reaction forces were extracted for analysis. Estimated quadriceps muscle forces were input into a muscle adaptation model to predict a meaningful increase in muscle cross-sectional area, defined in (DeFreitas et al., 2011). Results: Two distinct strategies were observed to cope with the increase in ground reaction forces as gravity increased. Hypogravity was associated with an ankle dominant strategy with increased range of motion and net plantarflexor moment that was not seen at the hip or knee, and the Rectus Femoris being the primary contributor to quadriceps muscle force. At 1 g, all three joints had increased range of motion and net extensor moments relative to 0.50 g, with the Vasti muscles becoming the main muscles contributing to quadriceps muscle force. Additionally, hip joint reaction force did not increase substantially as gravity increased, whereas the other two joints increased monotonically with gravity. The predicted volume of exercise needed to counteract muscle adaptations decreased substantially with gravity. Despite the ankle dominant strategy in hypogravity, the loading on the knee muscles and joint also increased, demonstrating this provided more information about MSK loading. Discussion: This approach, supplemented with muscle-adaptation models, can be used to compare MSK loading between exercises to enhance astronaut exercise prescription.

Vibration acceleration enhances proliferation, migration, and maturation of C2C12 cells and promotes regeneration of muscle injury in male rats.

Vibration acceleration (VA) using a whole-body vibration device is beneficial for skeletal muscles. However, its effect at the cellular level remains unclear. We aimed to investigate the effects of VA on muscles invitro and invivo using the C2C12 mouse myoblast cell line and cardiotoxin-induced injury in male rat soleus muscles. Cell proliferation was evaluated using the WST/CCK-8 assay and proportion of Ki-67 positive cells. Cell migration was assessed using wound-healing assay. Cell differentiation was examined by the maturation index in immunostained cultured myotubes and real-time polymerase chain reaction. Regeneration of soleus muscle in rats was assessed by recruitment of satellite cells, cross-sectional area of regenerated muscle fibers, number of centrally nucleated fibers, and conversion of regenerated muscle from fast- to slow-twitch. VA at 30 Hz with low amplitude for 10 min promoted C2C12 cell proliferation, migration, and myotube maturation, without promoting expression of genes related to differentiation. VA significantly increased Pax7-stained satellite cells and centrally nucleated fibers in injured soleus muscles on Day 7 and promoted conversion of fast- to slow-twitch muscle fibers with an increase in the mean cross-sectional area of regenerated muscle fibers on Day 14. VA enhanced the proliferation, migration, and maturation of C2C12 myoblasts and regeneration of injured rat muscles.