Natural fibres are increasingly used as reinforcements for thermoplastic composites. Additive manufacturing, also known as 3D printing, is a common material extrusion process using (bio)polymers ...reinforced with natural fibres. However, there is a lack of understanding of the effect of printing parameters on the mechanical properties involved in this new process, and more particularly in the case of Fused Deposition Modeling (FDM). Hygromorphic biocomposites represent a novel use of natural fibres for the production of original self-bending devices that actuate in a moisture gradient. By mimicking natural actuators and their bilayer microstructure adapted for seed dispersal, hygromorphic biocomposites take advantage of the hygro-elastic behaviour of natural fibres.
The FDM of wood fibre reinforced biocomposites leads to mechanical properties that are strongly dependent on printing orientation (0 or 90°) due to fibre anisotropy. Mechanical properties depend also on printing width (overlapping of filaments), with a lower Young's modulus than in the compressed samples. Indeed, printed biocomposites have a microstructure with relatively high porosity (around 20%) that conjointly leads to damage mechanisms but also water absorption and swelling.
The FDM of hygromorphic biocomposites enables a shift towards 4D printing since the material is able to evolve over time in response to an external stimulus. Typical microstructures achieved by printing could be used advantageously to produce biocomposites with a faster moisture-induced bending response compared to compressed samples.
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•Fused Deposition Moulding (FDM) of wood biocomposites is performed.•Mechanical properties and microstructure are characterized according to printing width and orientation.•Mechanical properties are relatively low due to high porosity level located in interlayer area.•Hygromorph biocomposites are designed following bio-inspiration approach.•Porosity induced by FDM could be turned as an advantage when hygromorph biocomposites is developed.
Amyloid fibrils represent a stable form of many misfolded proteins associated with numerous diseases. Among these are Parkinson’s disease (α-synuclein), Type II diabetes (islet amyloid polypeptide), ...and Alzheimer’s disease (amyloid β-peptide, Aβ). The appearance of Aβ fibrils in neural tissue is a hallmark of Alzheimer’s disease, and many studies have been conducted to determine and analyze the structure of these protein aggregates. The principal toxic species in Alzheimer’s disease are believed to be soluble, oligomeric aggregates of Aβ, but numerous studies have found that the insoluble fibrillated form of the peptide also contributes to neurotoxicity. Thus, to design therapeutic agents to combat the progression of Alzheimer’s disease, it is worthwhile to understand the thermodynamics of destabilizing these aggregates and the features that contribute to their stability. In this work, we present a systematic study of several factors that influence the stability of Aβ42 fibrils following in silico mutation. We have employed standard molecular dynamics, as well as center-of-mass pulling and umbrella sampling, to study the thermodynamics of peptide dissociation from the core of a model protofibril at physiological temperature. Results indicate that a finite level of hydration around the Asp23−Lys28 salt bridge is crucial to protofibril stability, while mutation of Phe19 to glycine has no effect on the binding free energy of the terminal peptide. Packing between Ile32 and the aliphatic portion of the Lys28 side chain serves to regulate the level of hydration in the core of the protofibril and thus rigidify the Asp23−Lys28 salt bridge. These observations are important for designing compounds that target Aβ aggregates; interrupting these native interactions may destabilize these assemblies and ameliorate their toxicity.
The aggregation cascade and peptide-membrane interactions of the amyloid β-peptide (Aβ) have been implicated as toxic events in the development and progression of Alzheimer’s disease. Aβ42 forms ...oligomers and ultimately plaques, and it has been hypothesized that these oligomeric species are the main toxic species contributing to neuronal cell death. To better understand oligomerization events and subsequent oligomer-membrane interactions of Aβ42, we performed atomistic molecular-dynamics (MD) simulations to characterize both interpeptide interactions and perturbation of model membranes by the peptides. MD simulations were utilized to first show the formation of a tetramer unit by four separate Aβ42 peptides. Aβ42 tetramers adopted an oblate ellipsoid shape and showed a significant increase in β-strand formation in the final tetramer unit relative to the monomers, indicative of on-pathway events for fibril formation. The Aβ42 tetramer unit that formed in the initial simulations was used in subsequent MD simulations in the presence of a pure POPC or cholesterol-rich raft model membrane. Tetramer-membrane simulations resulted in elongation of the tetramer in the presence of both model membranes, with tetramer-raft interactions giving rise to the rearrangement of key hydrophobic regions in the tetramer and the formation of a more rod-like structure indicative of a fibril-seeding aggregate. Membrane perturbation by the tetramer was manifested in the form of more ordered, rigid membranes, with the pure POPC being affected to a greater extent than the raft membrane. These results provide critical atomistic insight into the aggregation pathway of Aβ42 and a putative toxic mechanism in the pathogenesis of Alzheimer’s disease.
There is a general agreement that the most valid method of measuring peak lower-body mechanical power output (LBPP) in a countermovement jump (CMJ) is by analysis of the corresponding vertical ...component of the ground reaction force (VGRF)-time history of the jump. However, there is no published standard protocol. The purpose of this study was to establish a standard protocol. The variables necessary to define a valid and reliable CMJ method were: (a) vertical force range, (b) force sampling and integration frequency, (c) method of integration, (d) determination of body weight (BW), and (e) determination of the initiation of the CMJ. Countermovement jumps off a force platform (FP) were performed by 15 male professional rugby players. The 5 variables were then optimized to maximize the reliability and validity of the measure of LBPP. Errors of <1% (p ≤ 0.05) in the measurement of LBPP were obtained using the following specification: (a) 6 times BW (using a 16-bit analog to digital converter), (b) 1,000 Hz, (c) Simpson's rule or the trapezoidal rule, (d) mean VGRF for 1 second of quiet standing immediately before jump signal, and (e) 30 ms before the instant BW ± 5 SD is exceeded after the jump signal. Peak lower-body power output was most sensitive to variables 4 and 5. It was concluded that this study has established a standard protocol for the criterion method of measuring peak power in a CMJ using an FP. As all other estimates and less reliable methods of determining LBPP in a CMJ rely on the FP method for calibration, it is proposed that this protocol be used as the basis of future criterion measures using a FP.
The role of serrated polyps (SPs) as colorectal cancer precursor is increasingly recognised. However, the true prevalence SPs is largely unknown. We aimed to evaluate the detection rate of SPs ...subtypes as well as serrated polyposis syndrome (SPS) among European screening cohorts.
Prospectively collected screening cohorts of ≥1000 individuals were eligible for inclusion. Colonoscopies performed before 2009 and/or in individuals aged below 50 were excluded. Rate of SPs was assessed, categorised for histology, location and size. Age-sex-standardised number needed to screen (NNS) to detect SPs were calculated. Rate of SPS was assessed in cohorts with known colonoscopy follow-up data. Clinically relevant SPs (regarded as a separate entity) were defined as SPs ≥10 mm and/or SPs >5 mm in the proximal colon.
Three faecal occult blood test (FOBT) screening cohorts and two primary colonoscopy screening cohorts (range 1.426-205.949 individuals) were included. Rate of SPs ranged between 15.1% and 27.2% (median 19.5%), of sessile serrated polyps between 2.2% and 4.8% (median 3.3%) and of clinically relevant SPs between 2.1% and 7.8% (median 4.6%). Rate of SPs was similar in FOBT-based cohorts as in colonoscopy screening cohorts. No apparent association between the rate of SP and gender or age was shown. Rate of SPS ranged from 0% to 0.5%, which increased to 0.4% to 0.8% after follow-up colonoscopy.
The detection rate of SPs is variable among screening cohorts, and standards for reporting, detection and histopathological assessment should be established. The median rate, as found in this study, may contribute to define uniform minimum standards for males and females between 50 and 75 years of age.
Study and design of stability in GH5 cellulases Badieyan, Somayesadat; Bevan, David R.; Zhang, Chenming
Biotechnology and bioengineering,
January 2012, Letnik:
109, Številka:
1
Journal Article
Second order Differential Power Analysis (2O-DPA) is a powerful side-channel attack that allows an attacker to bypass the widely used masking countermeasure. To thwart 2O-DPA, higher order masking ...may be employed but it implies a nonnegligible overhead. In this context, there is a need to know how efficient a 2O-DPA can be, in order to evaluate the resistance of an implementation that uses first order masking and, possibly, some hardware countermeasures. Different methods of mounting a practical 2O-DPA attack have been proposed in the literature. However, it is not yet clear which of these methods is the most efficient. In this paper, we give a formal description of the higher order DPA that are mounted against software implementations. We then introduce a framework in which the attack efficiencies may be compared. The attacks we focus on involve the combining of several leakage signals and the computation of correlation coefficients to discriminate the wrong key hypotheses. In the second part of this paper, we pay particular attention to 2O-DPA that involves the product combining or the absolute difference combining. We study them under the assumption that the device leaks the Hamming weight of the processed data together with an independent Gaussian noise. After showing a way to improve the product combining, we argue that in this model, the product combining is more efficient not only than absolute difference combining, but also than all the other combining techniques proposed in the literature.
Terpene volatiles play important roles in plant-organism interactions as attractants of pollinators or as defense compounds against herbivores. Among the most common plant volatiles are homoterpenes, ...which are often emitted from night-scented flowers and from aerial tissues upon herbivore attack. Homoterpene volatiles released from herbivore-damaged tissue are thought to contribute to indirect plant defense by attracting natural enemies of pests. Moreover, homoterpenes have been demonstrated to induce defensive responses in plant—plant interaction. Although early steps in the biosynthesis of homoterpenes have been elucidated, the identity of the enzyme responsible for the direct formation of these volatiles has remained unknown. Here, we demonstrate that CYP82G1 (At3g25180), a cytochrome P450 monooxygenase of the Arabidopsis CYP82 family, is responsible for the breakdown of the C₂₀-precursor (E,E)-geranyllinalool to the insect-induced C₁₆-homoterpene (E,E)-4,8 12-trimethyltrideca-1,3,7, 11-tetraene (TMTT). Recombinant CYP82G1 shows narrow substrate specificity for (E,E)-geranyllinalool and its C₁₅-analog (E)-nerolidol, which is converted to the respective C₁₁-homoterpene (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT). Homology-based modeling and substrate docking support an oxidative bond cleavage of the alcohol substrate via syn-elimination of the polar head, together with an allylic C-5 hydrogen atom. CYP82G1 is constitutively expressed in Arabidopsis stems and inflorescences and shows highly coordinated herbivoreinduced expression with geranyllinalool synthase in leaves depending on the F-box protein COI-1. CYP82G1 represents a unique characterized enzyme in the plant CYP82 family with a function as a DMNT/TMTT homoterpene synthase.
Semantic dementia, including the semantic variant of primary progressive aphasia (svPPA), is strongly associated with TAR-DNA binding protein 43 (TDP-43) type C pathology. It provides a useful model ...in which to test the specificity of in vivo binding of the putative tau ligand
FAV-1451, which is elevated in frontotemporal lobar degeneration tauopathies.
Seven patients (five with svPPA and two with 'right' semantic dementia) and 12 healthy controls underwent positron emission tomography brain imaging with
FAV-1451. Two independent preprocessing methods were used. For both methods, all patients had clearly elevated binding potential (BP
(non-displaceable binding potential)) in temporal lobes, lateralising according to their clinical syndrome and evident in raw images. Region of interest analyses confirmed that BP
was significantly increased in temporal regions, insula and fusiform gyrus, consistent with those areas known to be most affected in semantic dementia. Hierarchical cluster analysis, based on the distribution of
FAV-1451 binding potential, separated semantic dementia from controls with 86% sensitivity and 100% specificity.
FAV-1451 binds in vivo regions that are likely to contain TDP-43 and not significant tau pathology. While this suggests a non-tau target for
FAV-1451, the pathological regions in semantic dementia do not normally contain significant levels of recently proposed 'off target' binding sites for
FAV-1451, such as neuronal monoamine oxidase or neuromelanin. Postmortem and longitudinal data will be useful to assess the utility of
FAV-1451 to differentiate and track different types of frontotemporal lobar degeneration.
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