Tissue Toughness Research Articles

A proposal for the combined analysis of bone quantity and quality of human cortical bone by quasi-brittle fracture mechanics

Quasi-brittle fracture mechanics is used to evaluate fracture of human cortical bone in aging. The approach is demonstrated using cortical bone bars extracted from one 92-year-old human male cadaver. In-situ fracture mechanics experiments in a 3D X-ray microscope are conducted. The evolution of the fracture process zone is documented. Fully developed fracture process zone lengths at peak load are found to span about three osteon diameters. Crack deflection and arrest at cement lines is a key process to build extrinsic toughness. Strength and toughness are found as size-dependent, not only for laboratory-scale experimental specimens but also for the whole femur. A scaling law for the length fracture process zone is used. Then, size-independent, tissue fracture properties are calculated. Linear elastic fracture mechanics applied to laboratory beam specimens underestimates the tissue toughness by 60%. Tissue fracture properties are used to predict the load capacity of the femur in bending within the range of documented data. The quasi-brittle fracture mechanics approach allows for the assessment of the combined effect of bone quantity and bone quality on fracture risk. However, further work is needed considering a larger range of subjects and in the model validation at the organ length scale.

Intestinal Villi-Inspired Mathematically Base-Layer Engineered Microneedles (IMBEMs) for Effective Molecular Exchange during Biomarker Enrichment and Drug Deposition in Diversified Mucosa.

The mucosa-interfacing systems based on bioinspired engineering design for sampling/drug delivery have manifested crucial potential for the monitoring of infectious diseases and the treatment of mucosa-related diseases. However, their efficiency and validity are severely restricted by limited contact area for molecular transfer and dissatisfactory capture/detachment capability. Herein, inspired by the multilayer villus structure of the small intestine that enables high nutrient absorption, a trigonometric function-based periodic pattern was fabricated and integrated on the base layer of the microneedle patch, exhibiting a desirable synergistic effect with needle tips for deep sample enrichment and promising molecular transfer, significantly improving the device-mucosa bidirectional interaction. Moreover, mathematical modeling and finite element analysis were adopted to visualize and quantify the microcosmic molecular transmission process, guiding parameter optimization in actual situation. Encouragingly, these intestinal villi-inspired mathematically base-layer engineered microneedles (IMBEMs) have demonstrated distinguished applicability among mucosa tissue with varying surface curvatures, tissue toughness, and local environments, and simultaneously, have gained favorable support from healthy volunteers receiving preliminary test of IMBEMs patches. Overall, validated by numerous in vitro and in vivo tests, the IMBEMs were confirmed to act as a promising candidate to facilitate mucosa-based sampling and topical drug delivery, indicating highly clinical translation potential.

Piglet Model for Modified Blalock-Taussig-Thomas Shunt Training

BackgroundThe Blalock-Taussig-Thomas shunt is one of the milestone procedures in cardiac surgery and a crucial operation for palliating blue babies. It is currently impractical to train new surgeons on infants even under the supervision of their mentors. A realistic training model for location, exposure, tissue toughness, and texture is required. The objective of this study was to determine whether the model is realistic and practical and to evaluate the quality of anastomosis performed by surgical trainees. MethodsPiglet heart and lung models were selected from piglets of 3 to 5 kg. Six cardiothoracic surgical residents participated in the program and performed the procedure. Subsequently, every trainee answered a standard questionnaire in terms of satisfaction in reality and practicality; the trainers evaluated the quality of the anastomosis. The median score of each item was analyzed and described. The quality of anastomosis was evaluated and analyzed similarly. ResultsMedian scores of satisfaction (14 questions) were 9, 10, 9, 9.5, 10, 9.5, 10, 9.5, 10, 8.5, 10, 8.5, 10, and 8. Median challenge scores (6 questions) were 10, 10, 10, 10, 10, 9.5, and 10. The median anastomosis evaluation score from 6 trainees was 25 (24-25). ConclusionsOur heart-lung simulation model is perhaps 1 of the most realistic simulations in practicality, visualization, exposure of the related structures, similar scenes to the real operation, and sense of touch and texture. Realistic models should be developed, but they should be inexpensive.

Assessment of glycosaminoglycan content in bone using Raman spectroscopy.

Glycosaminoglycans (GAGs) are responsible for preserving bone tissue toughness as well as regulating collagen formation and mineralization in the extracellular matrix. However, current methods for characterization of GAGs in bone are destructive, thus unable to capture in situ changes or differences in GAGs between experimental groups. As an alternative, Raman spectroscopy is a non-destructive method and can detect concurrent changes in GAGs and other bone constituents. In this study, we hypothesized that the two most prominent Raman peaks of sulfated GAGs (at ~1066cm-1 and at ~1378cm-1) could be used to detect differences in GAGs content of bone. To test this hypothesis, three experimental models were utilized: an in vitro model (enzymatic removal of GAGs from human cadaver bone), an ex vivo mouse model (biglycan KO vs. WT), and an ex vivo aging model (comparing cadaveric bone samples from young and old donors). All Raman measurements were compared to Alcian blue measurements to confirm the validity of Raman spectroscopy in detecting GAGs changes in bone. Irrespective of different models, it was found that the ~1378cm-1 peak in Raman spectra of bone was uniquely sensitive to changes of GAGs content in bone when normalized with respect to the phosphate phase (~960cm-1); i.e., 1378cm-1/960cm-1 (peak intensity ratio) or 1370-1385cm-1/930-980cm-1 (integrated peak area ratio). In contrast, the 1070cm-1 peak, which includes another major peak of GAGs (1066cm-1), seemed to be compromised to detect changes of GAGs in bone due to concurrent changes of carbonate (CO3) in the similar peak range. This study validates the ability of Raman spectroscopy to detect in situ treatment-, genotype-, and age-related changes in GAG levels of bone matrix.

Damage and Fracture Mechanics of Porcine Subcutaneous Tissue Under Tensile Loading.

Subcutaneous injection, which is a preferred delivery method for many drugs, causes deformation, damage, and fracture of the subcutaneous tissue. Yet, experimental data and constitutive modeling of these dissipation mechanisms in subcutaneous tissue remain limited. Here we show that subcutaneous tissue from the belly and breast anatomical regions in the swine show nonlinear stress-strain response with the characteristic J-shaped behavior of collagenous tissue. Additionally, subcutaneous tissue experiences damage, defined as a decrease in the strain energy capacity, as a function of the previously experienced maximum deformation. The elastic and damage response of the tissue are accurately described by a microstructure-driven constitutive model that relies on the convolution of a neo-Hookean material of individual fibers with a fiber orientation distribution and a fiber recruitment distribution. The model fit revealed that subcutaneous tissue can be treated as initially isotropic, and that changes in the fiber recruitment distribution with loading are enough to explain the dissipation of energy due to damage. When tested until failure, subcutaneous tissue that has undergone damage fails at the same peak stress as virgin samples, but at a much larger stretch, overall increasing the tissue toughness. Together with a finite element implementation, these data and constitutive model may enable improved drug delivery strategies and other applications for which subcutaneous tissue biomechanics are relevant.

Climate-driven shifts in kelp forest composition reduce carbon sequestration potential.

The potential contribution of kelp forests to blue carbon sinks is currently of great interest but interspecific variance has received no attention. In the temperate Northeast Atlantic, kelp forest composition is changing due to climate‐driven poleward range shifts of cold temperate Laminaria digitata and Laminaria hyperborea and warm temperate Laminaria ochroleuca. To understand how this might affect the carbon sequestration potential (CSP) of this ecosystem, we quantified interspecific differences in carbon export and decomposition alongside changes in detrital photosynthesis and biochemistry. We found that while warm temperate kelp exports up to 71% more carbon per plant, it decomposes up to 155% faster than its boreal congeners. Elemental stoichiometry and polyphenolic content cannot fully explain faster carbon turnover, which may be attributable to contrasting tissue toughness or unknown biochemical and structural defenses. Faster decomposition causes the detrital photosynthetic apparatus of L. ochroleuca to be overwhelmed 20 days after export and lose integrity after 36 days, while detritus of cold temperate species maintains carbon assimilation. Depending on the photoenvironment, detrital photosynthesis could further exacerbate interspecific differences in decomposition via a potential positive feedback loop. Through compositional change such as the predicted prevalence of L. ochroleuca, ocean warming may therefore reduce the CSP of such temperate marine forests.

Mistletoe infection changes arthropod community on its cactus host through indirect effects

Abstract Parasitic plants and herbivores show similarities in their interactions with host plants. Herbivore‐induced resistance/susceptibility in plants can scale up to the arthropod community. Similar evidence regarding parasitic plants is scarce. We evaluated the indirect effects initiated by the mistletoe Tristerix aphyllus on the arthropod community of the cactus Echinopsis chiloensis in the Chilean coastal desert. Field observations suggested that a stem‐borer beetle bores more brood chambers in mistletoe‐parasitised cacti than in non‐parasitised cacti, and that arthropods colonise these chambers. We compared tissue toughness, chamber density and morphology in mistletoe‐parasitised and non‐parasitised cacti. We also compared richness, total abundance, abundance per taxa, diversity and composition of the colonising arthropod community. Parasitised cacti showed a 14% reduction in tissue toughness. Chamber density in parasitised cacti was four times greater and chambers were larger: 35% more volume, an entrance‐opening area 30% greater, and twice the area of the maximum‐width section. Arthropod species richness and diversity were higher in chambers of parasitised cacti. Arthropod community composition was different in chambers of parasitised and non‐parasitised cacti. Thus, spiders and moths were more abundant in parasitised cacti, and pseudoscorpions, scolopendras, ants and flies were exclusively present there, while non‐parasitised cacti had no exclusive taxa. Mistletoe infection results in a richer, more diverse and distinct arthropod community on its cactus host, which occurs through induced susceptibility to stem‐borers whose brood chambers are colonised by arthropods. Tristerix aphyllus could be a key‐stone species in these arid ecosystems, where arthropod diversity is relatively low.

Removal of glycosaminoglycans affects the in situ mechanical behavior of extrafibrillar matrix in bone

Previous studies have shown that glycosaminoglycans (GAGs) in bone matrix, coupling with water in bone matrix, may play a significant role in toughening bone tissues. Since GAGs are most likely present only in the extrafibrillar matrix (EFM) of bone, we hypothesized that GAGs in EFM would have a major impact on bone tissue toughness. To confirm this conjecture, we removed GAGs ex vivo from human cadaveric bone samples using a protein deglycosylation mix kit and then examined the in situ mechanical behavior of mineralized collagen fibrils (MCFs) and the surrounding EFM of the samples, using a high-resolution atomic force microscopy (AFM). By testing the bone samples before and after removal of GAGs, we found that under the wet condition removal of GAGs resulted in an increase in the elastic modulus of both EFM and MCFs, whereas a significant decrease in plastic energy dissipation was observed mainly in EFM. In contrast, under the dry condition the removal of GAGs had little effects on the mechanical properties of either MCFs or EFM. These results suggest that both MCFs and EFM contribute to the plastic energy dissipation of bone, whereas in the presence of matrix water removal of GAGs significantly reduces the capacity of EFM in plastic energy dissipation, but not MCFs. In addition, GAGs may affect the elastic modulus of both EFM and MCFs. These findings give rise to new understanding to the underlying mechanism of GAGs in toughening of bone tissues.

Kelp-Associated Microbes Facilitate Spatial Subsidy in a Detrital-Based Food Web in a Shoreline Ecosystem

Microbes are ubiquitous but our knowledge of their effects on consumers is limited in benthic marine systems. Shorelines often form hotspots of microbial and detritivore activity due to the large amounts of detrital macrophytes that are exported from other coastal ecosystems, such as kelp forests, and accumulate in these systems. Shoreline ecosystems therefore provide a useful model system to examine microbial-detritivore interactions. We experimentally test whether bacteria in the biofilm of kelp provide a bottom-up influence on growth and reproductive output of detritivores in shorelines where detrital kelp accumulates, by manipulating the bacterial abundances on kelp (Ecklonia radiata). The growth rates for both male and female amphipods (Allorchestes compressa) were greater in treatments containing bacteria than those in which bacteria were reduced through antibiotic treatment, and this effect was greater for males offered aged kelp. The proportions of ovigerous females were greater when reared on kelp with intact bacteria, indicating a more rapid reproductive development in the presence of more bacteria. Bacterial abundance had little to no influence on nutrient content and palatability of kelp, based on tissue toughness, nitrogen and carbon content and C:N ratio. Thus, the most likely pathway for a microbial effect on detritivores was through feeding on kelp-associated bacteria. Regardless of the pathway, kelp-associated microbes have a strong influence on the fitness of a highly abundant detritivore that feeds preferentially on E. radiata in shoreline systems, and therefore form a hidden trophic step in this “brown” food web and a hotspot of secondary production.

Traits, strategies, and niches of liana species in a tropical seasonal rainforest

Plant functional traits and strategies hold the promise to explain species distribution, but few studies have linked multiple traits to multiple niche dimensions (i.e., light, water, and nutrients). Here, we analyzed for 29 liana species in a Chinese tropical seasonal rainforest how: (1) trait associations and trade-offs lead to different plant strategies; and (2) how these traits shape species’ niche dimensions. Eighteen functional traits related to light, water, and nutrient use were measured and species niche dimensions were quantified using species distribution in a 20-ha plot combined with data on canopy gaps, topographic water availability, and soil nutrients. We found a tissue toughness spectrum ranging from soft to hard tissues along which species also varied from acquisitive to conservative water use, and a resource acquisition spectrum ranging from low to high light capture and nutrient use. Intriguingly, each spectrum partly reflected the conservative–acquisitive paradigm, but at the same time, the tissue toughness and the resource acquisition spectrum were uncoupled. Resource niche dimensions were better predicted by individual traits than by multivariate plant strategies. This suggests that trait components that underlie multivariate strategy axes, rather than the plant strategies themselves determine species distributions. Different traits were important for different niche dimensions. In conclusion, plant functional traits and strategies can indeed explain species distributions, but not in a simple and straight forward way. Although the identification of global plant strategies has significantly advanced the field, this research shows that global, multivariate generalizations are difficult to translate to local conditions, as different components of these strategies are important under different local conditions.

Characterization of Microstructural Changes on Biglycan Induced Mice Bone by Low-Field Nuclear Magnetic Resonance.

A NMR spin-spin (T2) relaxation technique has been described for determining the porosity, and the bound water distribution in biglycan induced mouse bone and correlate to their mechanical properties. The technique of low-field proton NMR involves spin-spin relaxation and free induction decay (FID) measurements, and the computational inversion methods for decay data analysis. The CPMG T2 relaxation data can be inverted to T2 relaxation distribution and this distribution then can be transformed to a pore size distribution with the longer relaxation times corresponding to larger pores. The FID T2 relaxation data of dried bone (mobile water removed) can be inverted to T2 relaxation distribution and this distribution then can be transformed to bound and solid-like water distribution with the longest relaxation time corresponding to bound water component. These techniques are applied to quantify apparent changes in porosity, and bound water in controlled and biglycan knockout mouse bone. Overall bone porosity from CPMG T2 relaxation is determined using the calibrated NMR fluid volume from the proton relaxation data divided by overall bone volume. Ignore the physical sample differences, from the inversion FID T2 relaxation spectrum, the ratio of the bound to solid-like water components is used to calibrate the bound water inside bone, and the results can be used to correlated bone mechanical properties. Hydration status significantly affects the toughness of bone, and bound water has been considered as a biomarker for prediction of bone fragility fractures. In addition to the collagen phase, recent evidence shows that glycosaminoglycans (GAGs) of proteoglycans (PGs) in the extracellular matrix also play a pivotal role in regulating the tissue-level hydration status of bone, there by affecting the tissue-level toughness of bone. Furthermore, biglycan and decorin are two major types of PGs in bone reports. Biglycan knockout induced changes in GAGs, bound water, as well as bone tissue toughness. Among all subtypes of PGs, biglycan is identified as a major subtype in the bone mineral matrix. In this study, we used a biglycan mouse model and the obtained bone samples were measured by low-field NMR to determine the bone porosity and bound water changes, and used to predict if knockout of biglycan may affect the amount of bound water and subsequently lead to reduce toughness of bone.

Can flooding-induced greenhouse gas emissions be mitigated by trait-based plant species choice?

Intensively managed grasslands are large sources of the potent greenhouse gas nitrous oxide (N2O) and important regulators of methane (CH4) consumption and production. The predicted increase in flooding frequency and severity due to climate change could increase N2O emissions and shift grasslands from a net CH4 sink to a source. Therefore, effective management strategies are critical for mitigating greenhouse gas emissions from flood-prone grasslands. We tested how repeated flooding affected the N2O and CH4 emissions from 11 different plant communities (Festuca arundinacea, Lolium perenne, Poa trivialis, and Trifolium repens in monoculture, 2- and 4-species mixtures), using intact soil cores from an 18-month old grassland field experiment in a 4-month greenhouse experiment. To elucidate potential underlying mechanisms, we related plant functional traits to cumulative N2O and CH4 emissions. We hypothesized that traits related with fast nitrogen uptake and growth would lower N2O and CH4 emissions in ambient (non-flooded) conditions, and that traits related to tissue toughness would lower N2O and CH4 emissions in flooded conditions. We found that flooding increased cumulative N2O emissions by 97 fold and cumulative CH4 emissions by 1.6 fold on average. Plant community composition mediated the flood-induced increase in N2O emissions. In flooded conditions, increasing abundance of the grass F. arundinacea was related with lower N2O emissions; whereas increases in abundance of the legume T. repens resulted in higher N2O emissions. In non-flooded conditions, N2O emissions were not clearly mediated by plant traits related with nitrogen uptake or biomass production. In flooded conditions, plant communities with high root carbon to nitrogen ratio were related with lower cumulative N2O emissions, and a lower global warming potential (CO2 equivalent of N2O and CH4). We conclude that plant functional traits related to slower decomposition and nitrogen mineralization could play a significant role in mitigating N2O emissions in flooded grasslands.

Mechanics of linear microcracking in trabecular bone

Microcracking in trabecular bone is responsible both for the mechanical degradation and remodeling of the trabecular bone tissue. Recent results on trabecular bone mechanics have demonstrated that bone tissue microarchitecture, tissue elastic heterogeneity and tissue-level mechanical anisotropy all should be considered to obtain detailed information on the mechanical stress state. The present study investigated the influence of tissue microarchitecture, tissue heterogeneity in elasticity and material separation properties and tissue-level anisotropy on the microcrack formation process. Microscale bone models were executed with the extended finite element method. It was demonstrated that anisotropy and heterogeneity of the bone tissue contribute significantly to bone tissue toughness and the resistance of trabecular bone to microcrack formation. The compressive strain to microcrack initiation was computed to increase by a factor of four from an assumed homogeneous isotropic tissue to an assumed anisotropic heterogenous tissue.

Can traits predict individual growth performance? A test in a hyperdiverse tropical forest.

Summary The functional trait approach has, as a central tenet, that plant traits are functional and shape individual performance, but this has rarely been tested in the field. Here, we tested the individual‐based trait approach in a hyperdiverse Amazonian tropical rainforest and evaluated intraspecific variation in trait values, plant strategies at the individual level, and whether traits are functional and predict individual performance.We evaluated > 1300 tree saplings belonging to > 383 species, measured 25 traits related to growth and defense, and evaluated the effects of environmental conditions, plant size, and traits on stem growth.A total of 44% of the trait variation was observed within species, indicating a strong potential for acclimation. Individuals showed two strategy spectra, related to tissue toughness and organ size vs leaf display. In this nutrient‐ and light‐limited forest, traits measured at the individual level were surprisingly poor predictors of individual growth performance because of convergence of traits and growth rates.Functional trait approaches based on individuals or species are conceptually fundamentally different: the species‐based approach focuses on the potential and the individual‐based approach on the realized traits and growth rates. Counterintuitively, the individual approach leads to a poor prediction of individual performance, although it provides a more realistic view on community dynamics.

DMA and DETA thermal analysis of carrot during its drying at different air humidity

The outer part (myzoderma) of carrot was tested using dynamic mechanical analysis (DMA), in air with three different values of humidity (50, 70, and 90%) in temperature scans between 30 and 90 °C. Temperature plots of storage (SM i.e. elastic) and loss (LM i.e. inelastic) moduli were obtained. The DMA was combined with Dielectric thermal analysis (DETA). The tissue toughness decreased with increasing temperature; the kinetic analysis of the data led to four characteristic temperatures different for different air humidity; these characteristic temperatures divided temperature scale into temperature ranges A, B1, B2, and B3. The range A, limited for all tested cases with different humidity by 50 °C, is termed low temperature drying. With decreasing air humidity, the characteristic temperatures also decrease. The ranges B1, B2, and B3 represent the different stages of high temperature drying (initial – B1, rapid or main – B2, and final – B3). Part B2 can be understood as the temperature range where drying is most rapid and the role of plasmodesma destruction can play the fundamental role.

Evaluating ascending aortic aneurysm tissue toughness: Dependence on collagen and elastin contents

Ascending thoracic aortic aneurysms (ATAAs) can lead to a dissection or rupture of the aorta, causing death or disability of the patients. Surgical interventions used to treat this disease are associated with risks of mortality and morbidity. Several studies have investigated the rupture mechanisms of ATAAs; however, underlying reasons behind aortic rupture (failure) have not been fully elucidated and further investigations are necessary. The rupture of pathological aortic tissue is a local phenomenon resulting from defects or tears in the vessel wall. In this work, the toughness-based rupture properties of ATAAs have been examined.The toughness, biaxial tensile properties, and histological properties of aneurysmal and control human ascending thoracic aortas (ATAs) were characterized from four quadrants of surgically excised aortic rings. The aneurysmal tissue population included aortas from patients with bicuspid aortic valves (BAV) and tricuspid aortic valves (TAV). The toughness, incremental modulus, and thickness properties of the aortas were determined and compared regionally. Additionally, to further explore the rupture propensity of ATAAs, the inter-correlation of the toughness properties with histological characteristics have been explored. We found no correlation between toughness and incremental modulus. However, toughness decreased significantly with the amount of collagen. In the outer curvature, there was an increase in incremental modulus with collagen+elastin content, but a decrease in toughness. These results suggest tissue remodeling could affect toughness and stiffness differently in ascending aortic aneurysms.

Towards the characterisation of carotid plaque tissue toughness: Linking mechanical properties to plaque composition

The morphological manifestation of calcification within an atherosclerotic plaque is diverse and the response to cutting balloon angioplasty remains an elusive target to predict in the presence of extensive calcification. This study examines the resistance of plaque tissue to blade penetration by characterising the underlying toughness properties and stratifying the upper and lower scale toughness limits based on the strong mechanical influence of calcification. Mechanical toughness properties of the common, bifurcation and internal carotid artery (n=62) were determined using guillotine-cutting tests measuring the energy required to pass a surgical blade through a unit length of plaque tissue. The corresponding structural composition of the dissected plaque segments was characterised using Fourier transform infrared analysis, electron microscopy and energy dispersive x-ray spectroscopy. Mechanical results reveal a clear distinction in toughness properties within each region of the carotid vessel with significantly tougher properties localised in the bifurcation (p=0.004) and internal region (p=0.0003) compared to the common. The severity of the intra-plaque variance is highest in plaques with high toughness localised in the bifurcation region (p<0.05). Structural examination reveals that the diverse mechanical influence of the level of calcification present is characteristic of specific regions within the carotid plaque. The energy required to overcome the calcific resistance and propagate a controlled cut in the calcified tissue at each region varies further with the degree of plaque progression. The identification of the localised calcification characteristics is a key determinant in achieving successful dissection of the severely toughened plaque segments during cutting balloon angioplasty. Calcification plays a fundamental role in plaque tissue mechanics and demonstrates a diverse range of material moduli properties. This work addresses the characterisation of the toughness properties in human carotid plaque tissue using a fracture mechanics approach. Toughness determines the energy required to propagate a controlled cut in the plaque material. This parameter is crucial for predicting the cutting forces required during endovascular cutting balloon angioplasty intervention. Results demonstrate that a strong relationship exists between the structural calcification configurations, fracture mechanisms and associated toughness properties that are characteristic of specific regions within the carotid artery plaque. The identification of the morphological characteristics of localised calcification may serve as a valuable quantitative measure for cutting balloon angioplasty treatment.

The influence of composition and location on the toughness of human atherosclerotic femoral plaque tissue

The toughness of femoral atherosclerotic tissue is of pivotal importance to understanding the mechanism of luminal expansion during cutting balloon angioplasty (CBA) in the peripheral vessels. Furthermore, the ability to relate this parameter to plaque composition, pathological inclusions and location within the femoral vessels would allow for the improvement of existing CBA technology and for the stratification of patient treatment based on the predicted fracture response of the plaque tissue to CBA. Such information may lead to a reduction in clinically observed complications, an improvement in trial results and an increased adoption of the CBA technique to reduce vessel trauma and further endovascular treatment uptake.This study characterises the toughness of atherosclerotic plaque extracted from the femoral arteries of ten patients using a lubricated guillotine cutting test to determine the critical energy release rate. This information is related to the location that the plaque section was removed from within the femoral vessels and the composition of the plaque tissue, determined using Fourier Transform InfraRed spectroscopy, to establish the influence of location and composition on the toughness of the plaque tissue. Scanning electron microscopy (SEM) is employed to examine the fracture surfaces of the sections to determine the contribution of tissue morphology to toughness.Toughness results exhibit large inter and intra patient and location variance with values ranging far above and below the toughness of healthy porcine arterial tissue (Range: 1330–3035 for location and 140–4560J/m2 for patients). No significant difference in mean toughness is observed between patients or location. However, the composition parameter representing the calcified tissue content of the plaque correlates significantly with sample toughness (r=0.949, p<0.001). SEM reveals the presence of large calcified regions in the toughest sections that are absent from the least tough sections. Regression analysis highlights the potential of employing the calcified tissue content of the plaque as a preoperative tool for predicting the fracture response of a target lesion to CBA (R2=0.885, p<0.001). Statement of SignificanceThis study addresses a gap in current knowledge regarding the influence of plaque location, composition and morphology on the toughness of human femoral plaque tissue. Such information is of great importance to the continued improvement of endovascular treatments, particularly cutting balloon angioplasty (CBA), which require experimentally derived data as a framework for assessing clinical cases and advancing medical devices. This study identifies that femoral plaque tissue exhibits large inter and intra patient and location variance regarding tissue toughness. Increasing calcified plaque content is demonstrated to correlate significantly with increasing toughness. This highlights the potential for predicting target lesion toughness which may lead to an increased adoption of the CBA technique and also further the uptake of endovascular treatment.

Combined mechanical (DMA) and dielectric (DETA) thermal analysis of carrot at temperatures 30–90 °C

The outer part of carrot was tested using dynamic mechanical analysis (DMA), in air with 90% humidity between 30 and 90°C. Temperature plots of storage (SM i.e. elastic) and loss (LM i.e. inelastic) moduli were obtained. The SM and LM values were the basis for the calculation of the loss tangent (LT), the parameter expressing the ratio of inelastic to elastic parenchyma toughness. The DMA was followed by Dielectric thermal analysis (DETA). The tissue toughness decreased with increasing temperature; the kinetic analysis of the data led to two characteristic temperatures (approximately 50°C and 70°C) where the physical parameters changed their temperature dependence. The characteristic temperatures can serve as a basis of division of the whole temperature range into four parts (A–D). The DMA results supported phase transitions at temperatures below 70°C, whereas DETA strongly support changes observed at and above 70°C. These changes were interpreted as a consequence of changes and destructions of the cell membrane – plasmalemma. A similar analysis on other tissues gave similar but little different results supporting the idea of possible application of the method to study product differences.

Wave-induced changes in seaweed toughness entail plastic modifications in snail traits maintaining consumption efficacy: Commentary on Moliset al. 2015

Phenotypic plasticity – the capacity of a single genotype to produce multiple phenotypes in response to an organism's environment – is a wide spread phenomenon among marine intertidal organisms (Padilla & Savedo 2013). The marine intertidal is a dynamic habitat, with abiotic features including wave exposure, immersion time, salinity, nutrients and temperature varying among, and often within, sites. These abiotic factors directly influence the organisms that inhabit this area and also play a role in determining the type and strength of community interactions present such as predation, competition and facilitation (Menge & Sutherland 1987). A number of studies have elucidated the direct impact of abiotic and biotic factors on intertidal organisms’ phenotypes (Padilla & Savedo 2013). Fewer studies have examined community level responses to phenotypic changes in plastic organisms, and the majority of these have focused on the indirect impacts of predator presence on lower trophic levels through their behavioural modification of intermediate prey species (trait-mediated indirect effects; Dill, Heithaus & Walters 2003; Miner et al. 2005). In contrast, Molis et al. (2015) explored a relatively understudied species response to phenotypic plasticity: an herbivore's ability to plastically change the morphology of its feeding apparatus to match the structure of its phenotypically plastic algal food source. This cascade of phenotypic plasticity ultimately arises from an abiotic environmental factor, wave exposure, which distinguishes this study from those focused on the biotic factor of predator-mediated indirect effects (Dill, Heithaus & Walters 2003; Miner et al. 2005). Through a series of field and laboratory experiments, Molis et al. (2015) demonstrated that wave exposure mediates the phenotypically plastic trait of seaweed tissue toughness in Fucus vesiculosus, which subsequently impacts snail radula tooth length and cusp number in Littorina obtusata. Field surveys indicated a positive correlation between F. vesiculosus tissue toughness and increasing wave exposure. Transplant experiments in which F. vesiculosus blades transplanted from low to high wave exposure sites increased in tissue toughness confirmed the plasticity of this trait. Molis et al. (2015) also showed that snail preference for tougher or softer blades is dependent on the snail's site of origin, as snails from wave-protected sites possessed radulas with shorter teeth and fewer cusps. As with algal tissue toughness, snail radular features were found to be plastic, with snails from protected sites developing larger radular teeth and more cusps when provided tougher, wave exposed algal tissues as their only food source in the laboratory. There are two aspects of the Molis et al. (2015) study that distinguish it from previous work on phenotypic plasticity. First, as stated above, it focuses on an abiotically mediated cascade of phenotypic changes as opposed to the more frequently studied biotically mediated cascades. Secondly, this study was conducted in the two geographically distant intertidal areas of Nova Scotia and Helgoland. This type of geographic coverage is a rarity among similar studies, and it provides strong evidence that phenotypic plasticity linked to wave exposure is likely a general feature of both F. vesiculosus and L. obtusata. The findings of Molis et al. (2015) provide a basis for investigating similar abiotically mediated phenotypic plasticity cascades in other species and in response to a broader range of abiotic factors. For instance, there are now several reports of plastic radular features in marine snails in response to variation in their food source(s) (Padilla 1998; Andrade & Solferini 2006; Molis et al. 2015), indicating that phenotypically plastic radulas may be a common feature among marine snails. We can also hypothesize that other herbivores that are tightly linked to an intertidal algal food source may respond similarly to abiotically induced plasticity in their algal prey. Given that many algal species are notoriously morphologically plastic (Mathieson, Norton & Neushul 1981), so much so that modern taxonomic assessments must rely heavily on genetic sequencing rather than morphological identifications (e.g. Saunders 2005), it is possible that this type of interaction is a widespread yet overlooked component of the marine intertidal community. While numerous instances of phenotypic plasticity have been documented in the marine intertidal, many marine systems remain understudied. As highlighted by Padilla & Savedo (2013), the vast majority of marine phenotypic plasticity studies, including Molis et al. (2015), have been conducted in temperate intertidal zones with benthic organisms. Marine pelagic and subtidal benthic zones remain poorly studied, as do tropical and polar regions (Padilla & Savedo 2013). As these understudied regions are heavily impacted by anthropogenic activities, including habitat destruction, pollution and climate change (Halpern et al. 2007; Doney et al. 2012), it is vital to gain a better understanding of phenotypic plasticity as it relates to community interactions (Reed, Schindler & Waples 2011). This paper does not contain data.