The bulk of Earth's biological materials consist of few base substances-essentially proteins, polysaccharides, and minerals-that assemble into large varieties of structures. Multifunctionality arises ...naturally from this structural complexity: An example is the combination of rigidity and flexibility in protein-based teeth of the squid sucker ring. Other examples are time-delayed actuation in plant seed pods triggered by environmental signals, such as fire and water, and surface nanostructures that combine light manipulation with mechanical protection or water repellency. Bioinspired engineering transfers some of these structural principles into technically more relevant base materials to obtain new, often unexpected combinations of material properties. Less appreciated is the huge potential of using bioinspired structural complexity to avoid unnecessary chemical diversity, enabling easier recycling and, thus, a more sustainable materials economy.
The shrinking and swelling of wood due to moisture changes are intrinsic material properties that control and limit the use of wood in many applications. Herein, hygroscopic deformations of normal ...and compression wood of Chinese fir (
Cunninghamia lanceolata
Lamb. Hook.) were measured during desorption and absorption processes. The dimensional changes were observed in situ by an environmental scanning electron microscope and analyzed at different hierarchical levels (tissue, cell and cell wall). The relationship between moisture variation and hygroscopic deformation was measured. During initial desorption periods from 95 to 90 or 75% RH, an expansion of the lumen and a shrinkage of the cell wall were observed, revealing a non-uniform and directional deformation of single wood cells. The variation of shrinking or swelling at different hierarchical levels (tissue, cell and cell wall) indicates that the hygroscopic middle lamella plays a role in the deformation at the tissue level. Higher microfibril angles and helical cavities on the cell wall in compression wood correlate with a lower shrinking/swelling ratio. Normal wood showed a more pronounced swelling hysteresis than compression wood, while the sorption hysteresis was almost the same for both wood types. This finding is helpful to elucidate effects of micro- and ultrastructure on sorption. The present findings suggest that the sophisticated system of wood has the abilities to adjust the hygroscopic deformations by fine-tuning its hierarchical structures.
The microtensile properties of mechanically isolated compression wood (CW) and opposite wood (OW) tracheids of Chinese fir (
Cunninghamia lanceolata
) were investigated and discussed with respect to ...their structure. Major differences in the tensile modulus and ultimate tensile stress were found between CW and OW fibers. Compared to OW, CW showed a larger cellulose microfibril angle, less cellulose content and probably more pits, resulting in lower tensile properties. These findings contribute to a further understanding of the structural–mechanical relationships of Chinese fir wood at the cell and cell wall level, and provide a scientific basis for better utilization of plantation softwood.
The proportion of bark in tree trunks is in the range of ~ 10-20%. This large amount of material is currently mainly considered as a by- or even waste-product by the timber processing industry. ...Recently, efforts towards the use of bark have been made, e.g. as a raw material to harvest different chemical compounds or as an additive for wood particle boards. Our motivation for this work was to keep the bark in an almost natural state and explore alternative processes and applications for use. The traditional method of de-barking tree trunks by peeling was used to harvest large bark pieces. Two pieces of peeled bark were placed crosswise, with the rhytidom side (outer bark) facing each other. After different conditioning steps, bark pieces were hot pressed to panels without adding adhesives. These experiments on bark samples of different Central European tree species suggest that production of panels with species dependent properties is possible and feasible. This is a step towards producing sustainable panels by using a natural waste material, while retaining its beneficial structure and its natural chemical composition.
Velvet worms eject a fluid capture slime that can be mechanically drawn into stiff biopolymeric fibres. Remarkably, these fibres can be dissolved by extended exposure to water, and new regenerated ...fibres can be drawn from the dissolved fibre solution-indicating a fully recyclable process. Here, we perform a multiscale structural and compositional investigation of this reversible fabrication process with the velvet worm Euperipatoides rowelli, revealing that biopolymeric fibre assembly is facilitated via mono-disperse lipid-protein nanoglobules. Shear forces cause nanoglobules to self-assemble into nano- and microfibrils, which can be drawn into macroscopic fibres with a protein-enriched core and lipid-rich coating. Fibre dissolution in water leads to re-formation of nanoglobules, suggesting that this dynamic supramolecular assembly of mechanoresponsive protein-building blocks is mediated by reversible non-covalent interactions. These findings offer important mechanistic insights into the role of mechanochemical processes in bio-fibre formation, providing potential avenues for sustainable material fabrication processes.Velvet worms expel a fluid slime that, under shear force, forms stiff fibres that can be dissolved and then regenerated. Here, the authors reveal that the recyclability of these biopolymers relies on mechanoresponsive lipid-protein nanoglobules in the slime that reversibly self-assemble into fibrils.
Isolated single wood fibres with cellulose fibril angles from 10 to 43° were tested in microtensile tests under controlled temperature and relative humidity of 5, 50, 75, 90% and in the wet state. ...This systematic study provides experimental stiffness and strength data, calculated on cell wall cross sections. It has been shown that stiffness reduction with increasing moisture content is more pronounced in fibres with large cellulose fibril angles. Interestingly, stiffness reduction in fibres with low cellulose fibril angles has been observed for the fully hydrated state only. The experimental dataset was fed into a model to determine moisture dependent stiffness of the hemicellulose-lignin-matrix and the stresses acting on the fibrils and the matrix.
Purpose
To evaluate the relationship of neuroretinal layer thickness with sensitive measures of cardiovascular autonomic neuropathy in diabetic patients with non‐proliferative diabetic retinopathy ...(NPDR).
Methods
Twenty‐seven eyes of 27 patients with type 1 diabetes presenting with mild‐to‐moderate NPDR were compared to 27 healthy control (HC) eyes matched for age and gender. The total macular volume (TMV) and the volumes of individual neurosensory layers in the macula were analysed from spectral domain optical coherence tomography using automated layer segmentation. Cardiovascular autonomic regulation was assessed by short‐term power spectrum analysis of heart rate variability (HRV) before, during and after an orthostatic challenge.
Results
The patients had an age of 46 ± 12 years and diabetes since 28 ± 9 years. Diastolic and mean arterial pressure was lower in the patients compared to HCs. TMV (r = 0.58, p = 0.002), inner plexiform layer volume (IPLV; r = 0.39, p = 0.047) and inner nuclear layer volume (INLV; r = 0.60, p = 0.001) were associated with reduced recovery of low‐frequency (LF) spectral power of HRV after orthostatic load in diabetic patients but not in HCs. The response of LF spectral power during the orthostatic manoeuvre was blunted in patients compared to HCs (p = 0.02). Diabetes duration was negatively associated with TMV and INLV, whereas IPLV was significantly reduced in eyes with moderate NPDR compared to HCs.
Conclusion
The results indicate a correlation between inner retinal tissue loss and diminished autonomic regulation in type 1 diabetic patients with mild‐to‐moderate NPDR. The observed changes can be interpreted as congruent early signs of retinal and systemic neuropathy in diabetes.
Agarose hydrogels filled with cellulose nanowhiskers were strained in uniaxial stretching under different humidity conditions. The orientation of the cellulose whiskers was examined before and after ...testing with an X-ray laboratory source and monitored in situ during loading by synchrotron X-ray diffraction. The aim of this approach was to determine the process parameters for reorienting the cellulose nanowhiskers toward a preferential direction. Results show that a controlled drying of the hydrogel is essential to establish interactions between the matrix and the cellulose nanowhiskers which allow for a stress transfer during stretching and thereby promote their alignment. Rewetting of the sample after reorientation of the cellulose nanowhiskers circumvents a critical increase of stress. This improves the extensibility of the hydrogel and is accompanied by a further moderate alignment of the cellulose nanowhiskers. Following this protocol, cellulose nanowhiskers with an initial random distribution can be reoriented toward a preferential direction, creating anisotropic nanocomposites.
We report a facile one-step route to graft poly(ionic liquid)s (PILs) onto cellulose nanofibrils (CNFs). The dispersibility of the PIL-functionalized CNFs in water and various organic solvents could ...be tuned by the choice of the PIL-binding anion. We demonstrate that such omnidispersible PIL@CNF hybrids can be used to reinforce porous poly(ionic liquid) membranes.
To assess the effect of on-demand intranasal oxytocin administration on female sexual function and activity.
Randomized, prospective, double-blind, placebo-controlled, crossover trial with duration ...of 22 weeks.
Academic medical center.
Thirty pre-and postmenopausal women with sexual dysfunction.
Over 8 weeks, intranasal oxytocin (32 IU) or placebo self-administered by women within 50 minutes before sexual intercourse; after a washout period of 2 weeks, crossover with patients switched to the alternate group for another 8 weeks.
Primary outcome parameter: Female Sexual Function Index (FSFI); secondary outcome parameters: Female Sexual Distress Scale (FSDS), Sexual Quality of Life-Female (SQOL-F), Sexual Interest and Desire Inventory-Female (SIDI-F), and Hamilton depression scale (HDS).
After oxytocin and placebo, the FSFI score increased by 26% and 31%, SQOL-F score by 144% and 125%, and SIDI-F score by 29% and 23%, respectively (repeated measures analysis of variance between groups). After oxytocin and placebo, the FSDS score decreased by 36% and 45%, respectively (repeated measures analysis of variance between groups). There was no statistically significant treatment, sequence (placebo first/second), or interaction effect.
Long-term intranasal oxytocin and placebo administration both improved sexual function and symptoms of depression in women over time with no treatment, sequence (placebo first/second), or interaction effect.
NCT02229721.
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