Shear wave elastography can assess the in-vivo nonlinear mechanical behavior of heel-pad

This study combines non-invasive mechanical testing with finite element (FE) modelling to assess for the first time the reliability of shear wave (SW) elastography for the quantitative assessment of the in-vivo nonlinear mechanical behavior of heel-pad. The heel-pads of five volunteers were compressed using a custom-made ultrasound indentation device. Tissue deformation was assessed from B-mode ultrasound and force was measured using a load cell to calculate the force – deformation graph of the indentation test. These results were used to design subject specific FE models and to inverse engineer the tissue’s hyperelastic material coefficients and its stress – strain behavior. SW speed was measured for different levels of compression (from 0% to 50% compression). SW speed for 0% compression was used to assess the initial stiffness of heel-pad (i.e. initial shear modulus, initial Young’s modulus). Changes in SW speed with increasing compressive loading were used to quantify the tissue’s nonlinear mechanical behavior based on the theory of acoustoelasticity. Statistical analysis of results showed significant correlation between SW-based and FE-based estimations of initial stiffness, but SW underestimated initial shear modulus by 64%(±16). A linear relationship was found between the SW-based and FE-based estimations of nonlinear behavior. The results of this study indicate that SW elastography is capable of reliably assessing differences in stiffness, but the absolute values of stiffness should be used with caution. Measuring changes in SW speed for different magnitudes of compression enables the quantification of the tissue’s nonlinear behavior which can significantly enhance the diagnostic value of SW elastography.     

Decay resistance of ash,beech and maple wood modified with N-methylol melamine and a metal complex dye

This study evaluated the decay resistance of ash (Fraxinus excelsior L.), beech (Fagus sylvatica L.), and maple (Acer platanoides L.) wood impregnated by a full cell process with N-methylol melamine (NMM) and combined NMM-metal complex dye (NMM-BS) in aqueous solutions. Basidiomycete decay testing involved incubation with Coniophora puteana (brown rot) and Trametes versicolor (white rot) according to a modified EN 113 (1996) standard, while for the soft rot fungal resistance was evaluated following the standard ENv 807 (2001). NMM and NMM-BS modifications at a WPG range of 7–11% provided decay protection against brown rot resulting in a mass loss less than the required limit (3%). The NMM and NMM-BS modified wood showed increased resistance to white rot decay; however, a higher WPG is needed to prohibit attack from this hardwood specific fungus. The metal-complex dye alone revealed biocidal effects against basidiomycetes. An increased WPG in NMM or NMM-BS had a positive impact against soft rot decay and the lowest mass losses after 32 weeks of exposure were obtained with NMM modification at about 18–21% WPG. NMM modification at this WPG range, however, was not sufficient to protect the wood from soft rot decay. The wood of beech and maple showed slightly higher resistance to all decay types than ash, probably due to the poorer degree of modification of the latter.     

Effect of rocker shoes and running speed on lower limb mechanics and soft tissue vibrations

Previous studies have shown a possible effect of running speed and the sole material of footwear on lower-limb mechanics and soft tissue vibrations, while little information has been offered concerning the influence of the shape of the footwear’s sole. The purpose of this study is to assess the effect of running speed and rocker shoes on muscular activity, ground reaction force, and soft tissue vibrations. Twenty participants performed heel-toe running with two shoes, differentiated only by their sole shape (i.e. rocker and non-rocker), at four running speeds. Ground reaction force and electromyograms of the gastrocnemius medialis and vastus lateralis were measured, and soft tissue accelerations of the same muscles were recorded with tri-axial accelerometers. A continuous wavelet transform was applied to the accelerometer’s signals to analyse them in the time-frequency domain. The rocker of the shoes did not change the muscular activations, ground reaction force, nor power of soft tissue vibrations. In opposite, increased running speed led to an augmentation of all of the measured parameters. Interestingly, running speed augmentation led to a greater increase in high frequencies component of soft tissue vibrations (25–50 Hz, 242%) than lower ones (8–25 Hz, 111%). Consequently, we indicated a 10% increase in the relative part of the high frequencies of the total power. In conclusion, although rocker shoes have shown an effect on lower-limb kinetics in some studies, no influence on soft tissue vibration is denoted. By contrast, soft tissue vibrations may be modulated by changing running speed.     

Complementary (secondary) metabolites in an octocoral competing with a scleractinian coral: effects of varying nutrient regimes

Competitive interactions between two sessile, epibenthic species were investigated on the Great Barrier Reef (GBR) in the presence and absence of added nutrients, as part of the Enrichment of Nutrients on Coral Reefs Experiment (ENCORE). Sarcophyton ehrenbergi Marenzeller (Octocorallia: Alcyonacea), an alcyonacean soft coral, and Pocillopora damicornis (Linnaeus), a scleractinian coral, were relocated and placed in contact with each other on large plastic grids on each of 12 micro-atolls within the One Tree Island (OTI) lagoon (23°30′S, 152°96′E, GBR). These micro-atolls were allocated in equal-sized groups to three enrichment treatments (addition of nitrogen, N; addition of phosphorus, P; addition of both nitrogen and phosphorus, N+P) and one control. Non-relocated (NR) and relocated colonies were also monitored as controls. After relocation and 1 year of nutrient enrichment, concentrations of a terpenoid complementary metabolite—sarcophytoxide—and wax esters were analyzed in colonies of S. ehrenbergi that had been exposed to elevated concentrations of N, P, N+P and compared with colonies on the non-nutrient-enriched control. Non-relocated control colonies from the natural environment were monitored over a period of 1 year and compared to colonies relocated to the control micro-atolls to assess handling effects. Analyses were performed on non-interacting S. ehrenbergi colonies, S. ehrenbergi colonies in experimental contact with P. damicornis colonies, and on non-interacting S. ehrenbergi colonies from the site of initial collection. Significant differences were found between sarcophytoxide levels in colonies of S. ehrenbergi in contact with P. damicornis vs. control/non-contact colonies; contact colonies had higher levels of this metabolite. Non-relocated control colonies of S. ehrenbergi exhibited significantly higher levels of sarcophytoxide than relocated control colonies. Augmentation of nutrient levels in micro-atolls significantly increased sarcophytoxide levels in S. ehrenbergi colonies relative to colonies on the control micro-atolls, although this response was not strong. Concentrations of fatty esters increased significantly through time in S. ehrenbergi colonies in their natural setting (non-relocated controls). This variability was not observed in relocated colonies in the treatment and control micro-atolls, irrespective of contact with P. damicornis. Concentrations of fatty esters in colonies of S. ehrenbergi in contact with P. damicornis were significantly lower than control/non-contact colonies, indicating that there is a cost in terms of stored energy reserves for the production of additional complementary metabolites when involved in competition for space. Augmentation of P levels in micro-atolls induced significant increases in fatty ester levels within S. ehrenbergi colonies vs. colonies in control micro-atolls, or in micro-atolls treated with added N or N+P together. These findings indicate that interspecific competition for space between a scleractinian coral and an alcyonacean soft coral and/or changes in the environmental nutrient regime can influence concentrations of complementary/secondary metabolites in the alcyonacean coral and the organism's stored energy reserves.     

Prey selection and predatory impact of four major sea stars on a soft bottom subtidal community

We dived at regular intervals (8-, 12- or 24-h) over periods up to 24 days to quantify the feeding activities of identified sea stars along permanent transects in the upper sediment bottom zone (8-11 m deep). In this habitat, large individuals of four sea stars predominated. The diet of Asterias vulgaris (molluscs and echinoderms) was intermediate between that of Leptasterias polaris (mainly molluscs) and that of Crossaster papposus (mainly echinoderms), whereas the diet of Solaster endeca strongly differed from the other sea stars, as it only fed on holothuroids. Calculation of the Ivlev electivity index indicated little or no selection for many abundant prey species, whereas some rare prey in this zone (e.g., Mytilus edulis) were strongly selected. We quantified prey size selection, and observed evidence of selection on smaller individuals when feeding on infaunal bivalves (possibly the deeper burying of larger individuals limited attacks) and selection of larger individuals when feeding on epifaunal prey (possibly to maximize energetic intake). We observed A. vulgaris feeding on Mya truncata, which had been captured by L. polaris (kleptoparasitism) and this bivalve disappeared from the diet of A. vulgaris in areas where we experimentally removed L. polaris. Estimations of foraging rates over 100 days relative to prey availability indicated strong interactions among the sea stars themselves. C. papposus likely have a strong impact on conspecifics, L. polaris and A. vulgaris, and A. vulgaris on L. polaris. In contrast, <1% of total biomass of the most abundant prey of L. polaris (M. truncata) and C. papposus (Strongylocentrotus droebachiensis) was consumed in 100 days.     

Measurement of mechanical forces generated by plant P-protein aggregates (forisomes)

Mechanical forces generated by forisomes were measured using a microfabricated polymer cantilever sensor. The forces were simultaneously measured in both the longitudinal and radial directions. Sensors were fabricated from polystyrene using the sacrificial layer micromolding process. The sensor response was simulated using finite element analysis. Forces in the longitudinal direction ranged from 84 to 136 nN and forces in the radial direction were 22–61 nN. This device offers a new approach to measuring small magnitude biological forces. In addition, the ability to accurately measure forces generated by forisomes is an important step toward their implementation as functional structures in microdevices.     

Morphological features of Class I,II and III malocclusions of Saudi adolescents

AimsThis cross-sectional study compared and contrasted the morphological characteristics of Class I, II and III malocclusions in an adolescent Saudi population.MethodsAdolescent Saudis with Angle’s Class I, II and III malocclusions were selected from orthodontic patients’ records. Angular and linear measurements were compared between the three groups. Cephalometric analysis was performed using the VistadentOC® software. Multifactorial ANOVA for angular and linear measurements between and within groups.ResultsOrthodontic records of 300 patients were included. There was no significant difference between and within groups in age and distribution of Angle’s classification, p > 0.05. Multifactorial ANOVA showed that there were significant interactions between gender and malocclusions in skeletal, dental and soft tissue measurements, p < 0.05. There were significant differences in the sagittal and vertical skeletal measurements between groups, p < 0.05. The dental measurements were also significantly different in most of the measurements (p < 0.05). Moreover, there were significantly different readings among the groups in the soft tissue analysis.ConclusionMorphological characteristics of adolescent Saudis show unique differences between gender and malocclusions, more so in Class III malocclusions. Class II and III malocclusions also show skeletal differences amongst the groups.     

A death assemblage of priapulid worms from the Middle Cambrian Burgess Shale

A slab of Burgess Shale (Middle Cambrian), displaying an incomplete exoskeleton of the large arthropod Sidneyia inexpectans and encompassed by nine specimens of the priapulid worm Ottoia prolifica, is interpreted as a death assemblage, with the worms once living off or feeding around a carcass or freshly moulted instar of Sidneyia. Death is thought to have been caused by an obrution event that preserved the organisms in situ.