Mechanical characterisation of the layer-specific, viscoelastic properties of the human oesophagus is crucial in furthering the development of devices emerging in the field, such as robotic endoscopic biopsy devices, as well as in enhancing the realism, and therefore effectiveness, of surgical simulations. In this study, the viscoelastic and stress-softening behaviour of the passive human oesophagus was investigated through ex vivo cyclic mechanical tests. Due to restrictions placed on the laboratory as a result of COVID-19, only oesophagi from cadavers fixed in formalin were allowed for testing. Three oesophagi in total were separated into their two main layers and the mucosa–submucosa layer was investigated. A series of uniaxial tensile tests were conducted in the form of increasing stretch level cyclic tests at two different strain rates: 1% s\(^{-1}\) and 10% s\(^{-1}\). Rectangular samples in both the longitudinal and circumferential directions were tested to observe any anisotropy. Histological analysis was also performed through a variety of staining methods. Overall, the longitudinal direction was found to be much stiffer than the circumferential direction. Stress-softening was observed in both directions, as well as permanent set and hysteresis. Strain rate-dependent behaviour was also apparent in the two directions, with an increase in strain rate resulting in an increase in stiffness. This strain rate dependency was more pronounced in the longitudinal direction than the circumferential direction. Finally, the results were discussed in regard to the histological content of the layer, and the behaviour was modelled and validated using a visco-hyperelastic matrix-fibre model.
Anthropogenic environmental change affects organisms by exposing them to enhanced sensory stimuli that can elicit novel behavioural responses. A pervasive feature of the built environment is artificial nocturnal lighting, and brightly lit urban areas can influence organism abundance, distribution and community structure within proximate landscapes. In some cases, the attractive or disorienting effect of artificial light at night can draw animals into highly unfavourable habitats, acting as a macroscale attractive ecological sink. Despite their significance for animal ecology, identifying cases of these phenomena and determining their effective scales and the number of organisms impacted remains challenging. Using an integrated set of remote-sensing observations, we quantify the effect of a large-scale attractive sink on nocturnal flights of an outbreak insect population in Las Vegas, USA. At the peak of the outbreak, over 45 million grasshoppers took flight across the region, with the greatest numbers concentrating over high-intensity city lighting. Patterns of dusk ascent from vegetated habitat toward urban areas suggest a daily pull toward a time-varying nocturnal attractive sink. The strength of this attractor varies with grasshopper density. These observations provide the first macroscale characterization of the effects of nocturnal urban lighting on the behaviour of regional insect populations and demonstrate the link between insect perception of the built environment and resulting changes in spatial and movement ecology. As human-induced environmental change continues to affect insect populations, understanding the impacts of nocturnal light on insect behaviour and fitness will be vital to developing robust large-scale management and conservation strategies. 相似文献
Anatomical analyses found that leaves of Euphorbia nicaeensis ssp. glareosa are isolateral, amphistomatous, with two layers of palisade cells on the adaxial and one on the abaxial side. Laticifers
are present by vascular bundles, in palisade and spongy tissue. Stem laticifers are located in the pericyclic ring, adjacent
to the phloem, in cylinder parenchyma and medullar rays. The structure of pleiochasium and dichasium peduncle is similar to
the stem structure. Plants from typical steppe habitat show more xeromorphic features. Phytochemical screening of extracts
showed presence of catecholes, flavonoids, tannins, saponins, free quinone derivatives and absence of anthocyanins, leucoanthocyanins,
alkaloids, steroid compounds and essential oils. Our results showed that the examined taxon was partially susceptible to the
action of reactive oxygen species, such as O2·− and ·OH. The higher quantities of ROS thus provoked an antioxidative response from the plant, both in an enzymatic and non-enzymatic
manner. Stable anatomical structure, presence and distribution of laticifers and effective antioxidant properties when exposed
to ROS, make Euphorbia nicaeensis subsp. glareosa potentially interesting for further pharmaceutical and phytochemical examinations. 相似文献
Changes in antioxidant systems in soybean and associated weeds (Ambrosia artemisiifolia L., Chenopodium album L., Convolvulus arvensis L and Sinapis arvensis L.) were studied in relation to treatment with herbicides linuron and dimethenamid in the field experiment. Differences in
the total superoxide dismutase (SOD) and catalase (Cat) activities were observed in plants after application of herbicide
formulation. Quantities of superoxide (O2.-) and hydroxyl (·OH) radicals and malonyldialdehyde (MDA), reduced glutathione (GSH) and total polyphenols content were
also determined. In addition to this, potential antioxidant activity of the plant ethanolic extracts were assessed based on
the scavenging activity of stable DPPH free radicals. Results obtained suggest that plants investigated 1) expressed different
antioxidant systems in response to herbicide treatment; 2) enzymatic and non-enzymatic protective mechanisms were complementary;
3) some weed species showed distinctive and combined activity of several biochemical parameters, such as Ambrosia artemisiifolia. 相似文献
Chemically diverse fragment hits of focal adhesion kinase (FAK) were discovered by surface plasmon resonance (SPR) screening of our in-house fragment library. Site specific binding of the primary hits was confirmed in a competition setup using a high-affinity ATP-site inhibitor of FAK. Protein crystallography revealed the binding mode of 41 out of 48 selected fragment hits within the ATP-site. Structural comparison of the fragment binding modes with a DFG-out inhibitor of FAK initiated first synthetic follow-up optimization leading to improved binding affinity. 相似文献