Active Structural Elements Research Articles

Search for optimal parameters of active structural suspension elements by determining their integral stiffness and damping characteristics

Search for optimal parameters of active structural suspension elements by determining their integral stiffness and damping characteristics

Cobalt-phenolic nanoparticles-driven self-assembly of hyaluronic acid hydrogels providing a multifactorial approach for chronic wound management

Chronic wounds are persistent non-healing lesions whose complex management is due to the interplay of multiple factors promoting chronicity, such as oxidative stress, overexpressed enzyme activities impeding the tissue repair and bacterial contamination. Currently marketed chronic wound dressings are designed mainly to absorb wound exudate, and at most to release antimicrobial agents, usually ionic silver. However, an effective wound repair requires addressing the multifactorial nature of the wound in a holistic approach. This study explores the potential of metal phenolic network (MPN) nanoparticles (NPs), comprised of epigallocatechin gallate (EGCG) and cobalt, as active agents and structural elements in wound dressings. The MPN NPs were able to generate reactive oxygen species (ROS), disturb bacterial membrane, and inhibit the biofilm of both gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa. Owing to the high interfacial activity of their phenolic shells, the NPs drove the self-assembly of thiolated hyaluronic acid (THA) hydrogels featuring injectability, self-healing, stimuli-responsive NPs delivery in wound microenvironment, and control over deleterious enzyme activities, oxidative stress and bacterial colonisation. Specifically, the hydrogels inhibited matrix metalloproteinases (MMPs) and myeloperoxidase (MPO) by 60 and 80 %, respectively, and achieved 4-log reduction of S. aureus and 2-log reduction of P. aeruginosa concentrations. Finally, the hydrogels were in-vivo validated in a mouse animal model, showing lack of toxicity and similar wound healing efficiency as an antibiotic-containing commercial product.

Definition of the most commonly used ceramic brick for construction in Ecuador: Type and dimensions

In Ecuador, 95.9% of housing is built with the use of masonry. Current construction practice in Ecuador shows that masonry is mainly used as enclosing or partition elements and they are not considered as part of the resistant structural system even though masonry walls can work as an active structural element and their work is defined by their geometry and the mechanical properties of the bricks, mortar and their contact interaction. The aim of this work is to characterise the type and geometry of the most commonly used ceramic brick for construction in Ecuador and the particularities of its production. For this propose, field data were collected in 48.9% of the Ecuadorian territory, where 79.19% of the country's population is concentrated and statistical data processing was performed. The results show that the production of bricks in Ecuador is mainly artisanal and 92% of the factories produce solid bricks. The research showed that there are no scientific works on the geometrical characterisation of bricks in Ecuador. The data analysis shows that there is a regional influence in the average brick dimensions, where bricks produced in the coastal region are 35 × 19 × 7 cm; in the central-northern Andes 28.0 × 11.0 × 9.0 cm; in the southern Andes 25.7 × 13.0 × 7. 5 cm with CVlength = 1.21%, CVwidth = 1.31%, CVheight = 3.07%; and, in the Amazon region 25.1 × 11.8 × 7.2 cm, with CVlength = 0.92%, CVwidth = 1.27 %, CVheight = 2.36%. An important identified fact is that only 4.8% of brick manufacturers in Ecuador comply with the national standard dimensions.

Antarctic aldehyde dehydrogenase from Flavobacterium PL002 as a potent catalyst for acetaldehyde determination in wine

Latest solutions in biotechnologies and biosensing targeted cold-active extremozymes. Analysis of acetaldehyde as a relevant quality indicator of wine is one example of application that could benefit from using low-temperatures operating catalysts. In search of novel aldehyde dehydrogenases (ALDH) with high stability and activity at low temperatures, the recombinant S2-ALDH from the Antarctic Flavobacterium PL002 was obtained by cloning and expression in Escherichia coli BL21(DE3). Structural and phylogenetic analyses revealed strong protein similarities (95%) with psychrophilic homologs, conserved active residues and structural elements conferring enzyme flexibility. Arrhenius plot revealed a conformational shift at 30 °C, favoring catalysis (low activation energy) at lower temperatures. In addition to a broad substrate specificity with preference for acetaldehyde (Km = 1.88 mM), this enzyme showed a high tolerance for ethanol (15%) and several salts and chelators (an advantage for wine analysis), while being sensitive to mercury (I50 = 1.21 µM). The neutral optimal pH (7.5) and the stability up to 40 °C and after lyophilization represent major assets for developing S2-ALDH-based sensors. An enzymatic electrochemical assay was developed for acetaldehyde detection in wines with proven accuracy in comparison with the reference spectrophotometric method, thus evidencing the potential of S2-ALDH as effective biocatalyst for industry and biosensing.

Similarity-Based Virtual Screen Using Enhanced Siamese Deep Learning Methods.

Traditional drug production is a long and complex process that leads to new drug production. The virtual screening technique is a computational method that allows chemical compounds to be screened at an acceptable time and cost. Several databases contain information on various aspects of biologically active substances. Simple statistical tools are difficult to use because of the enormous amount of information and complex data samples of molecules that are structurally heterogeneous recorded in these databases. Many techniques for capturing the biological similarity between a test compound and a known target ligand in LBVS have been established. However, despite the good performances of the above methods compared to their prior, especially when dealing with molecules that have homogeneous active structural elements, they are not satisfied when dealing with molecules that are structurally heterogeneous. Deep learning models have recently achieved considerable success in a variety of disciplines due to their powerful generalization and feature extraction capabilities. Also, the Siamese network has been used in similarity models for more complicated data samples, especially with heterogeneous data samples. The main aim of this study is to enhance the performance of similarity searching, especially with molecules that are structurally heterogeneous. The Siamese architecture will be enhanced using two similarity distance layers with one fusion layer to further improve the similarity measurements between molecules and then adding many layers after the fusion layer for some models to improve the retrieval recall. In this architecture, several methods of deep learning have been used, which are long short-term memory (LSTM), gated recurrent unit (GRU), convolutional neural network-one dimension (CNN1D), and convolutional neural network-two dimensions (CNN2D). A series of experiments have been carried out on real-world data sets, and the results have shown that the proposed methods outperformed the existing methods.

A pH-powered mechanochemical engine regulates the buoyancy of Chaoborus midge larvae

The freshwater aquatic larvae of the Chaoborus midge are the world's only truly planktonic insects, regulating their buoyancy using two pairs of internal air-filled sacs, one in the thorax and the other in the seventh abdominal segment. In 1911, August Krogh demonstrated the larvae's ability to control their buoyancy by exposing them to an increase in hydrostatic pressure.1 However, how these insects control the volume of their air-sacs has remained a mystery. Gas is not secreted into the air-sacs, as the luminal gas composition is always the same as that dissolved in the surrounding water.1,2 Instead, the air-sac wall was thought to play some role.3-6 Here we reveal that bands of resilin in the air-sac's wall are responsible for the changes in volume. These bands expand and contract in response to changes in pH generated by an endothelium that envelops the air-sac. Vacuolar type H+ V-ATPase (VHA) in the endothelium acidifies and shrinks the air-sac, while alkalinization and expansion are regulated by the cyclic adenosine monophosphate signal transduction pathway. Thus, Chaoborus air-sacs function as mechanochemical engines, transforming pH changes into mechanical work against hydrostatic pressure. As the resilin bands interlaminate with bands of cuticle, changes in resilin volume are constrained to a single direction along the air-sac's longitudinal axis. This makes the air-sac functionally equivalent to a cross-striated pH muscle and demonstrates a unique biological role for resilin as an active structural element.

Anomaly detection via blockchained deep learning smart contracts in industry 4.0

The complexity of threats in the ever-changing environment of modern industry is constantly increasing. At the same time, traditional security systems fail to detect serious threats of increasing depth and duration. Therefore, alternative, intelligent solutions should be used to detect anomalies in the operating parameters of the infrastructures concerned, while ensuring the anonymity and confidentiality of industrial information. Blockchain is an encrypted, distributed archiving system designed to allow for the creation of real-time log files that are unequivocally linked. This ensures the security and transparency of transactions. This research presents, for the first time in the literature, an innovative Blockchain Security Architecture that aims to ensure network communication between traded Industrial Internet of Things devices, following the Industry 4.0 standard and based on Deep Learning Smart Contracts. The proposed smart contracts are implementing (via computer programming) a bilateral traffic control agreement to detect anomalies based on a trained Deep Autoencoder Neural Network. This architecture enables the creation of a secure distributed platform that can control and complete associated transactions in critical infrastructure networks, without the intervention of a single central authority. It is a novel approach that fuses artificial intelligence in the Blockchain, not as a supportive framework that enhances the capabilities of the network, but as an active structural element, indispensable and necessary for its completion.

Multidisciplinary multi-objective design optimization of an active morphing wing section

Design and optimization of morphing wings are of current research interest as they promise increasing efficiency and flexibility of future aircraft. A challenging task is to find structural layouts of morphing wings that enable aerodynamically optimized shape changes without defining the target shape a priori. The current paper addresses this task and presents a method that combines the optimization of the active structure of a wing section, parameterized by Lindenmayer cellular systems, with an aerodynamic evaluation. Neither the structural layout nor the target shape has to be defined a priori. This aim is achieved by a multidisciplinary optimization using evolutionary algorithms with aerodynamic and structural objectives. The developed method allows to optimize the topology of the internal structure, the placement of linear contraction, and expansion actuators as well as the setting of their actuation degree concurrently. It is shown that the present approach allows to find optimized internal layouts containing active structural elements for morphing wing sections.

Analysis of high-resolution aeromagnetic (HRAM) data of Lower Benue Trough, Southeastern Nigeria, for hydrocarbon potential evaluation

ABSTRACT The analyses of high-resolution aeromagnetic (HRAM) data of lower Benue Trough in southeastern Nigeria have delineated sections of the basin with requisite sedimentary thickness that could support the generation of oil and gas from right-type organic-matter rich source rock as well as identified intra-sedimentary structural framework that could aid hydrocarbon migration and restrain generated hydrocarbon within available reservoirs. The susceptibility and Analytic Signal (AS) maps derived from processed Gaussian-filtered and Reduced to Pole at Low Latitude (RTPLL) aeromagnetic data discriminate crystalline basement rocks from the sedimentary units. Likewise, many relatively shallow, short (900–1600 m) intra-geologic terrain linear structures and fewer long, deeper (>1.5–43 km) inter-geologic terrains crustal linear structures which reduce in population but increase in lateral extent and depth with increasing continuation distances were delineated from the processed Tilt Derivative (TDR) and the Horizontal components of the Tilt Derivatives grids at different Upward Continuation distances. Euler Deconvolution depth-weighting analyses determined depth to magnetic sources which ranges in value from 120 m above to 5 km below the Minna reference datum. Regions having sedimentary thickness in excess of 3 km with active intra-sedimentary structural elements qualify for further petroleum exploration campaign using other detailed geological and geophysical tools.

ROLE OF ACTIVE STRUCTURAL ELEMENTS IN LIFE CYCLE OF BUILDING CONSTRUCTIONS

During the life cycle of building constructions, a complex of interconnected and interdependent processes and stages of structural changes are implemented that ensure the safety of their functioning. The structural elements that determines through their existence in the structure of any composite, the conditions of the life history of the construction-system are cracks, inner surfaces of partition and residual deformations. The selected elements belong to the conditionally invisible parts of the material structure. Cracks, internal interfaces and residual deformations can be distinguished as active structural elements, as they are able to react to any influences in the same tempo-rhythm, predeterminations the timely manifestation of structural adaptation (self-organization). This ensures external and internal safety of constructions during operation. However, cracks, inner surfaces of partition and deformities can shorten the life history of the construction, taking it to the path of degradation and death. Thus, cracks, inner surfaces of partition and deformations perform both a structural and destructive role in the life cycle of a construction. Therefore, an important task should be considered an analysis of the role of active elements in the life cycle of building constructions. The carried out analysis contributes to solving the problems related to improvement of safety of structures and products functioning due to directed guidance of active elements in the form of cracks and internal interfaces with mandatory consideration of the influence of residual deformations. To quantify the change of total length of cracks and inner surfaces of partition can be through the coefficients of damage Kd and Kd1. Increasing structural diversity of concrete and expanded clay concrete contributes to the organization of structures in which the distribution of initial cracks prevents them from growing to dimensions dangerous to the structure.

Optimal Actuator Placement and Static Load Compensation for Euler-Bernoulli Beams with Spatially Distributed Inputs

Adaptive structures in civil engineering are based on active structural elements. In this paper, an active beam element is considered with potentially multiple fluidic inputs spatially distributed over the beam’s length. It is modeled by a one-dimensional beam equation. The inputs are realized as torque inputs, where the torque is proportional to the pressure of the fluid. A method to calculate the optimal input values analytically depending on a given static load case is presented in the first part of the paper. In the second part, by generalizing the static load using a sufficient number of discrete loads evenly distributed along the beam, optimal actuator positions can be calculated for a given number of actuators. The cost function is based on extending the idea of the Gramian compensability matrix to systems governed by spatially distributed ordinary differential equations. Since the number of actuators can be a design variable, this yields a Pareto front supporting the user in selecting an appropriate number. A fluidic actuator serves as example to illustrate the potential of the proposed placement algorithm.

Bottom-up Layer-by-Layer Assembling of Antibacterial Freestanding Nanobiocomposite Films.

In this study, freestanding nanobiocomposite films were obtained by the sequential deposition of biopolymer-capped silver nanoparticles (AgNPs) and hyaluronic acid (HA). At first, dispersions of AgNPs decorated with chitosan (CS) or aminocellulose (AC) were synthesized by applying high intensity ultrasound. These polycationic nanoentities were layer-by-layer assembled with the HA polyanion to generate stable 3D supramolecular constructs, where the biopolymer-capped AgNPs play the dual role of active agent and structural element. SEM images of the assemblies revealed gradual increase of thickness with the number of deposited bilayers. The composites of ≥50 bilayers were safe to human cells and demonstrated 100% antibacterial activity against Staphylococcus aureus and Escherichia coli. Moreover, the films containing CSAgNPs brought about the total prevention of biofilm formation reducing the cells surface adherence by up to 6 logs. Such nanobiocomposites could serve as an effective barrier to control bacterial growth on injured skin, burns, and chronic wounds.

Spatial instability of the rift in the St. Paul multifault transform fracture system, Atlantic Ocean

The structure of the acoustic basement of the eastern part of the St. Paul multifault transform fracture system hosts rift paleovalleys and a paleonodal depression that mismatch the position of the currently active zones. This displacement zone, which is composed of five fault troughs, is unstable in terms of the position of the rift segments, which jumped according to redistribution of stresses. The St. Paul system is characterized by straightening of the transform transition between two remote segments of the Mid-Atlantic Ridge (MAR). The eastern part of the system contains anomalous bright-spot-like reflectors on the flattened basement, which is a result of atypical magmatism, that forms the standard ridge relief of the acoustic basement. Deformations of the acoustic basement have a presedimentation character. The present-day deformations with lower amplitude in comparison to the basement are accompanied by acoustic brightening of the sedimentary sequence. The axial Bouguer anomalies in the east of the system continue to the north for 120 km from the active segments of the St. Paul system. Currently seismically active segments of the spreading system are characterized by increasing amplitudes of the E–W displacement along the fault troughs. Cross-correlation of the lengths of the active structural elements of the MAR zone (segments of the ridge and transform fracture zones of displacement) indicates that, statistically, the multifault transform fracture system is a specific type of oceanic strike-slip faults.

In vitro structure-toxicity relationship of chalcones in human hepatic stellate cells.

Xanthohumol (XN), the major prenylated chalcone from hops (Humulus lupulus L.), has received much attention within the last years, due to its multiple pharmacological activities including anti-proliferative, anti-inflammatory, antioxidant, pro-apoptotic, anti-bacterial and anti-adhesive effects. However, there exists a huge number of metabolites and structurally-related chalcones, which can be expected, or are already known, to exhibit various effects on cells. We have therefore analyzed the effects of XN and 18 other chalcones in a panel, consisting of multiple cell-based assays. Readouts of these assays addressed distinct aspects of cell-toxicity, like proliferation, mitochondrial health, cell cycle and other cellular features. Besides known active structural elements of chalcones, like the Michael system, we have identified several moieties that seem to have an impact on specific effects and toxicity in human liver cells in vitro. Based on these observations, we present a structure-toxicity model, which will be crucial to understand the molecular mechanisms of wanted effects and unwanted side-effects of chalcones.

Reversible gelation of cells using self-assembling hydrophobically-modified biopolymers: towards self-assembly of tissue.

Polymer hydrogels have long been used to hold and culture biological cells within their three-dimensional (3-D) matrices. Typically, in such cases, the cells are passively entrapped in a mesh of polymer chains. Here, we demonstrate an alternate approach where cells serve as active structural elements (crosslinks) within a polymer gel network. The polymers used in this context are hydrophobically modified (hm) derivatives of common biopolymers such as chitosan and alginate. We show that hm-polymers rapidly transform a liquid suspension of cells into an elastic gel. In contrast, the native biopolymers (without hydrophobes) do not cause such gelation. Gelation occurs because the hydrophobes on the polymer get embedded within the hydrophobic interiors of cell bilayer membranes. The polymer chains thus connect the cells into a 3-D sample-spanning network, with the cells serving as the junctions in the network. We demonstrate that a variety of cell types, including blood cells, endothelial cells, and breast cancer cells can be gelled by this approach. Cells gelled by hm-alginate are shown to remain viable within the network. Also, since the crosslinking mechanism is based on hydrophobic interactions, we show that the addition of supramolecules with hydrophobic binding pockets can reverse the gelation and release the cells. Cell-gels can be employed as injectable biomaterials since the connections in the network are susceptible to shear, but recover rapidly once shear is stopped. The overall approach provides a simple route towards the directed assembly of cell clusters and potentially to living tissue.

Structural limits on force production and shortening of smooth muscle

This study determined the factors that limit force production and shortening in two smooth muscles having very different relationships between active and passive force as a function of muscle length. The rat anococcygeus muscle develops active force over the range of lengths 0.2-2.0× the optimum length for force production (Lo). Passive tension due to extension of the resting muscle occurs only at lengths exceeding Lo. In contrast, the rabbit taenia coli develops force in the range of lengths 0.4-1.1 Lo, and passive force which is detectable at 0.56 Lo, increases to ~0.45 maximum active force at Lo, and increases sharply with further extension. The anococcygeus muscle can shorten to 0.2 Lo and the taenia coli to 0.4 Lo. Dynamic stiffness and energy usage at short muscle lengths suggest that the limit of shortening in the taenia coli, in contrast to the anococcygeus muscle, is not due to a failure of cross bridge interaction. Phosphorylation of the regulatory myosin light chains in intact muscles decreased to a small extent at short lengths compared to the decrease in force production. The differences in force production and the extent of shortening in the two muscles was maintained even when, following permeabilization, the myosin light chains were irreversibly phosphorylated with ATPγS, indicating that differences in activation played little, if any role. Ultrastructural studies on resting and activated muscles show that the taenia coli, which is rich in connective tissue (unlike the anococcygeus muscle) undergoes marked cellular twisting and contractile filament misalignment at short lengths with compression of the extracellular matrix. As a result, force is not transmitted in the longitudinal axis of the muscle, but is dissipated against an internal load provided by the compressed extracellular matrix. These observations on two very different normal smooth muscles reveal how differences in the relative contribution of active and passive structural elements determine their mechanical behavior, and how this is potentially modified by remodeling that occurs in disease and in response to changes in functional demand.

Structural Basis for the Regulation of Protein Kinase A by Activation Loop Phosphorylation

The catalytic subunit of cAMP-dependent protein kinase (PKA) is a member of the AGC group of protein kinases. Whereas PKA has served as a structural model for the protein kinase superfamily, all previous structures of the catalytic subunit contain a phosphorylated activation loop. To understand the structural effects of activation loop phosphorylation at Thr-197 we used a PKA mutant that does not autophosphorylate at Thr-197. The enzyme crystallized in the apo-state, and the structure was solved to 3.0 Å. The N-lobe is rotated by 18° relative to the wild-type apoenzyme, which illustrates that the enzyme likely exists in a wide range of conformations in solution due to the uncoupling of the N- and C-lobes. Several regions of the protein including the activation loop are disordered in the structure, and there are alternate main chain conformations for the magnesium positioning loop and catalytic loop causing a complete loss of hydrogen bonding between these two active site structural elements. These alterations are reflected in a 20-fold decrease in the apparent phosphoryl transfer rate as measured by pre-steady-state kinetic methods.

Damping Behaviour of Vibrating Shape Memory Alloy Rods Investigated by a Novel Constitutive Model

AbstractHysteretic behaviour of shape memory alloys (SMAs) is highly important for design and applicability of these materials in active structural elements like rods. Especially the damping performance of SMAs depend strongly on their hysteretic characteristics. Experimental investigations show the influences of stress on the hysteretic cycle. The current study shows some computational results of a constitutive model which is capable to investigate the effect of an external applied stress field on the hysteretic cycle according to a recently developed method on the basis of statistical mechanics method. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Optimal Placement of Active Elements in Space Truss Structures with Random Parameters Using Simulated Annealing

Piezoelectric active structural elements with built-in sensing and actuation function and feedback control are used to suppress vibration in adaptive truss structures. The problems of optimal placement and feedback gain of these active members are two important issues, which should be addressed in the design of adaptive truss structures. An efficient optimal placement strategy has been developed using minimum control energy dissipating over an infinite time interval. The nearly optimal placement of active members is consistently treated through the use of the control energy dissipating over an infinite time interval within the framework of the simulated annealing algorithm. Moreover, considering the material characteristics (modulus of elasticity and density of material), the geometric characteristics (the length and cross-sectional area of truss members), and external force such as the random variables, a mathematical model with reliability constraints on stress and displacement has been developed and using a probabilistic optimization technique the optimal velocity feedback gain of active members has been obtained. Illustrative examples are used to demonstrate the effectiveness of this methodology. It has been shown that the deterministic approach cannot provide reliable optimum design values.

Analog Controller Design for an Active Damping Element

The ‘Smart Disc’ is an active structural element to be used for damping vibrations in high-precision machines. It is based on a piezoelectric position actuator and a collocated piezoelectric force sensor. Active damping is realised by a feedback loop. In order to miniaturise the electronics involved in the Smart Disc concept, the sensor amplifier, the controller electronics, and the actuator amplifier may be integrated into an analog circuit based on a single operational amplifier. Controller design then boils down to proper dimensioning of a first-order lowpass filter with three electric components: one capacitor and two resistors.