Prediction of forming effects in UD-NCF by macroscopic forming simulation – Capabilities and limitations

Unidirectional non-crimp fabrics (UD-NCF) provide the highest lightweight potential among dry textile materials. Compared to multiaxial NCF, the fabric layers in UD-NCF enable a more targeted tailoring. Compared to woven fabrics, the fibres of UD-NCF are straight without weakening undulations. However, the formability of UD-NCF is more challenging compared to woven fabrics. The yarns are bonded by a stitching and the deformation behaviour highly depends on this stitching and on the slippage between the stitching and the fibre yarns. Moreover, distinct local draping effects occur, like gapping and fibre waviness, which can have a considerable impact on the mechanical performance. Such local effects are particularly challenging or even impossible to be predicted by macroscopic forming simulation. The present work applies a previously published macroscopic UD-NCF modelling approach to perform numerical forming analyses and evaluate the prediction accuracy of forming effects. In addition to fibre orientations and shear angles, as investigated in previous work, the present work also provides indication for fibre area ratios, gapping, transverse compaction and fibre waviness. Moreover, the prediction accuracy is validated by comparison with experimental tests, where full-field strains of inner plies are captured by prior application of dots onto the fibre yarns, by measuring them via radiography and applying a photogrammetry software. The modelling approach provides good prediction accuracy for fibre orientations, shear strains and fibre area ratio. Conversely, normal fibre strains, indicating fibre waviness, and transverse strains, indicating gapping, show some deviations due to the multiscale nature of UD-NCF that cannot be captured entirely on macroscopic scale.

Frameshift mutation in myostatin gene by zinc-finger nucleases results in a significant increase in muscle mass in Meishan sows

Myostatin (MSTN) is a negative regulator of skeletal muscle growth and development. A significant increase in skeletal muscle was observed in Mstn^−/− mice compared with wild-type mice. So far, there has been no report on porcine MSTN mutations leading to skeletal muscle hypertrophy. In this report a MSTN frameshift mutation missing 11 nucleotides in exon 2 was introduced into Meishan pigs by zinc finger nuclease (ZFN) technology. ZFN-edited MSTN^−/− Meishan pigs were successfully produced by a cloning method of somatic cell nucleus transfer. Results from slaughter experiments indicated that lean meat yield increased 16.53% in about 80 kg (10-months-old) MSTN^−/− Meishan sows compared with their corresponding wild-type counterparts. The lean percentage of carcass from MSTN^−/− sows was 61.20% vs 48.25% for MSTN^+/− sows and 44.67% for wild-type sows. The fat of MSTN^−/− sows was significantly lower than that of MSTN^+/− and wild-type sows. The loin eye area of MSTN^−/− Meishan sows (56.42 cm²) was greater than that of MSTN^+/− (37.39 cm²) and wild-type (26.26 cm²) sows. The muscle fibre area of longissimus muscle in wild-type Meishan sows (1 946 μm²) was significantly greater than that of MSTN^+/− (1 324 μm²) and MSTN⁻^/− (1 419 μm²) sows. Moreover the significantly increased skeletal muscle in these MSTN^−/− Meishan sows was mainly due to the increase in the number of myofibres rather than to hypertrophy. Compared with wild-type Meishan sows, it was noted that myofibres had transformed from type I to IIB in MSTN^−/− Meishan sows. Our present study demonstrated that frameshift mutation in MSTN by ZFN technology led to a significant increase in muscle mass and a significant decrease in fat content in Meishan sows.

Finite element analysis of natural fiber composites using a self-updating model

The aim of the current work was to illustrate the effect of the fibre area correction factor on the results of modelling natural fibre-reinforced composites. A mesoscopic approach is adopted to represent the stochastic heterogeneity of the composite, i.e. a meso-structural numerical model was prototyped using the finite element method including quasi-unidirectional discrete fibre elements embedded in a matrix. The model was verified by the experimental results from previous work on jute fibres but is extendable to every natural fibre with cross-sectional non-uniformity. A correction factor was suggested to fine-tune both the analytical and numerical models. Moreover, a model updating technique for considering the size-effect of fibres is introduced and its implementation was automated by means of FORTRAN subroutines and Python scripts. It was shown that correcting and updating the fibre strength is critical to obtain accurate macroscopic response of the composite when discrete modelling of fibres is intended. Based on the current study, it is found that consideration of the effect of flaws on the strength of natural fibres and inclusion of the fibre area correction factor are crucial to obtain realistic results.

Feed Restriction and Muscle Fibre Characteristics of Pectoralis Major in Broiler Chickens

The aim of the study was to evaluate the effect of one-week quantitative feed restriction (in days 8-14 of age) on histological characteristics of musculus pectoralis major in broiler chickens during the fattening period. Cockerels of Ross 308 (1215 chicken) were divided into 3 groups: ad libitum fed (AL; 3 × 135), restricted 80% of AL (R80; 3 × 135), and with limited feed intake 65% of AL (R65; 3 × 135). Eight cockerels per group were slaughtered in weekly intervals from day 14 of age till the end of experiment at 35 days to determine changes in the muscle fibre characteristics. The number of muscle fibres in pectoralis major decreased (P ≤ 0.001) with increasing age. Fibre cross sectional area was s ignificantly (P ≤ 0.027) affected by the interaction of group and age. At the end of feed restriction at 14 days all groups had similar fibre area (519-539 μm2), the differences between groups were observed at 35 days of age with the largest fibre area in R65 chickens (2296 μm2), while R80 did not differ from AL (1728 μm2 and 1667 μm2). There was no effect of feeding regime on giant muscle fibre incidence.

Daily chocolate milk consumption does not enhance the effect of resistance training in young and old men: a randomized controlled trial

Older and younger men completed 12 weeks of resistance training and ingested either 500 mL of chocolate milk or placebo daily. Training increased strength in both age groups (p < 0.05), with no supplementation effect. Type I muscle fibre area increased with training (p = 0.008) with no effect of age or supplementation. Type II fibre area increased (p = 0.014) in young men only with no supplementation effect. Chocolate milk did not enhance skeletal muscle hypertrophy following training.

A pilot study to determine whether differences exist in histochemical properties between the trapezius and extensor carpi radialis brevis muscles in women with work-related myalgia

To investigate fibre-type abnormalities in women with work-related myalgia (WRM), tissue samples were extracted from their trapezius (TRAP) and the extensor carpi radialis brevis (ECRB) muscles and compared with healthy controls (CON). For the ECRB samples (CON, n = 6; WRM, n = 11), no differences (P > 0.05) were found between groups for any of the properties examined, namely fibre-type (I, IIA, IIX, IIAX) distribution, cross-sectional fibre area, capillary counts (CC), capillary to fibre area ratio, and succinic dehydrogenase activity. For the TRAP samples (CON, n = 6; WRM, n = 8), the only difference (P < 0.05) observed between groups was for CC (CON > WRM), which was not statistically significant (P > 0.05) when age was used a covariant. A comparison of the properties of these 2 muscles in the CON group indicated a higher (P < 0.05) and lower (P < 0.05) percentage of type I and type IIA fibres, respectively, in the TRAP as well as higher (P < 0.05) CC, which was not specific to fibre type. These preliminary results suggest that the properties employed to characterize fibre types do not differentiate CON from WRM for either the TRAP or ECRB. As a consequence, the role of inherent fibre-type differences between these muscles in the pathogenesis of WRM remains uncertain.

Can increases in capillarization explain the early adaptations in metabolic regulation in human muscle to short-term training?

To investigate the hypothesis that increases in fibre capillary density would precede increases in oxidative potential following training onset, tissue was extracted from the vastus lateralis prior to (0 days) and following 3 and 6 consecutive days of submaximal cycle exercise (2 h·day–1). Participants were untrained males (age = 21.4 ± 0.58 years; peak oxygen consumption = 46.2 ± 1.6 mL·kg–1·min–1; mean ± standard error (SE)). Tissue was assessed for succinic dehydrogenase activity (SDH) by microphotometry and indices of capillarization based on histochemically assessed area and capillary counts (CC) in specific fibre types. Three days of training (n = 13) resulted in a generalized decrease (p < 0.05) in fibre area (–14.2% ± 3.0%; mean ± SE) and increase (p < 0.05) in CC/Area (20.4% ± 2.7%) and no change in either CC or SDH activity. Following 6 days of treatment (n = 6), increases (p < 0.05) in CC (18.2% ± 4.2%), CC/Area (28.9% ± 3.2%), and SDH activity (22.9% ± 6.0%) occurred that was not specific to major fibre type. No changes in either fibre area or fibre-type distribution were observed with additional training. We conclude that increases in angiogenic-based capillary density and oxidative potential occur coincidentally following training onset, while increases in capillary density, mediated by reductions in fibre area, represent an initial isolated response, the significance of which may be linked to the metabolic alterations that also result.