Control and modelling of continuum robots are challenging tasks for robotic researchers. Most works on modelling are limited to piecewise constant curvature. In many cases they neglect to model the ...actuators or avoid a continuum approach. In particular, in the latter case this leads to a complex model hardly implemented. In this work, a geometrically exact steady-state model of a tendon-driven manipulator inspired by the octopus arm is presented. It takes a continuum approach, fast enough to be implemented in the control law, and includes a model of the actuation system. The model was experimentally validated and the results are reported. In conclusion, the model presented can be used as a tool for mechanical design of continuum tendon-driven manipulators, for planning control strategies or as internal model in an embedded system.
This work addresses the inverse kinematics problem of a bioinspired octopus-like manipulator moving in three-dimensional space. The bioinspired manipulator has a conical soft structure that confers ...the ability of twirling around objects as a real octopus arm does. Despite the simple design, the soft conical shape manipulator driven by cables is described by nonlinear differential equations, which are difficult to solve analytically. Since exact solutions of the equations are not available, the Jacobian matrix cannot be calculated analytically and the classical iterative methods cannot be used. To overcome the intrinsic problems of methods based on the Jacobian matrix, this paper proposes a neural network learning the inverse kinematics of a soft octopus-like manipulator driven by cables. After the learning phase, a feed-forward neural network is able to represent the relation between manipulator tip positions and forces applied to the cables. Experimental results show that a desired tip position can be achieved in a short time, since heavy computations are avoided, with a degree of accuracy of 8% relative average error with respect to the total arm length.
Cephalopods (i.e., octopuses and squids) are being looked upon as a source of inspiration for the development of unmanned underwater vehicles. One kind of cephalopod-inspired soft-bodied vehicle ...developed by the authors entails a hollow, elastic shell capable of performing a routine of recursive ingestion and expulsion of discrete slugs of fluids which enable the vehicle to propel itself in water. The vehicle performances were found to depend largely on the elastic response of the shell to the actuation cycle, thus motivating the development of a coupled propulsion-elastodynamics model of such vehicles. The model is developed and validated against a set of experimental results performed with the existing cephalopod-inspired prototypes. A metric of the efficiency of the propulsion routine which accounts for the elastic energy contribution during the ingestion/expulsion phases of the actuation is formulated. Demonstration on the use of this model to estimate the efficiency of the propulsion routine for various pulsation frequencies and for different morphologies of the vehicles are provided. This metric of efficiency, employed in association with the present elastodynamics model, provides a useful tool for performing a priori energetic analysis which encompass both the design specifications and the actuation pattern of this new kind of underwater vehicle.
Despite the use of chemical fungicides, fungal diseases have a major impact on the yield and quality of plant produce globally and hence there is a need for new approaches for disease control. ...Several groups have examined the potential use of antifungal plant defensins for plant protection and have produced transgenic plants expressing plant defensins with enhanced resistance to fungal disease. However, before they can be developed commercially, transgenic plants must pass a series of strict regulations to ensure that they are safe for human and animal consumption as well as the environment. One of the requirements is rapid digestion of the transgene protein in the gastrointestinal tract to minimize the risk of any potential allergic response. Here, we examine the digestibility of two plant defensins, NaD1 from
Nicotiana alata
and SBI6 from soybean, which have potent antifungal activity against major cereal pathogens. The native defensins were not digestible in simulated gastrointestinal fluid assays. Several modifications to the sequences enhanced the digestibility of the two small proteins without severely impacting their antifungal activity. However, these modified proteins did not accumulate as well as the native proteins when transiently expressed
in planta
, suggesting that the protease-resistant structure of plant defensins facilitates their stability
in planta
.
Metformin is known to be rarely associated with lactic acidosis, a serious condition with a poor prognosis.
To review the National Pharmacovigilance Network of the Italian Medicines Agency reporting ...cases of metformin-associated lactic acidosis.
The National Pharmacovigilance Network of the Italian Medicines Agency, was searched for cases of lactic acidosis that occurred in a 10 years period (from November 2001 to October 2011). Data were analyzed, to identify associated clinical features. A systematic literature research was performed to identify other large case series on metformin associated lactic acidosis.
Metformin was the antidiabetic drug most frequently associated with lactic acidosis in the assessed period. Metformin-associated lactic acidosis was the most frequent serious adverse reaction related to metformin reported to the national authority (18.2% of all 650 adverse drug reactions reported). There were 59 cases of metformin-associated lactic acidosis (mortality rate of 25.4%). In most patients (89.8%) there was at least one risk factor for the occurrence of lactic acidosis. The predictors of death were low arterial blood pH and absence of acute renal failure. The systematic research of the literature identified only six case-series with more than 30 patients.
This is the second largest case series ever reported on metformin-associated lactic acidosis. We confirmed that this rare complication of metformin is frequently fatal. Death can be predicted when the patient arrive in the hospital with low pH and, not intuitively, if the patient has no acute kidney injury. Risk minimisation measures taken at national level to prevent this serious complication are described.
We have isolated a protein-disulfide isomerase (PDI) from Oldenlandia affinis (OaPDI), a coffee family (Rubiaceae) plant that accumulates knotted circular proteins called cyclotides. The novel plant ...PDI appears to be involved in the biosynthesis of cyclotides, since it co-expresses and interacts with the cyclotide precursor protein Oak1. OaPDI exhibits similar isomerase activity but greater chaperone activity than human PDI. Since domain c of OaPDI is predicted to have a neutral pI, we conclude that this domain does not have to be acidic in nature for PDI to be a functional chaperone. Its redox potential of -157 ± 4 mV supports a role as a functional oxidoreductase in the plant. The mechanism of enzyme-assisted folding of plant cyclotides was investigated by comparing the folding of kalata B1 derivatives in the presence and absence of OaPDI. OaPDI dramatically enhanced the correct oxidative folding of kalata B1 at physiological pH. A detailed investigation of folding intermediates suggested that disulfide isomerization is an important role of the new plant PDI and is an essential step in the production of insecticidal cyclotides.
Heterogeneous Underwater Swarm of Robotic Fish Iacoponi, S.; Hanbaly, M.; Infanti, A. ...
IOP conference series. Materials Science and Engineering,
10/2023, Letnik:
1292, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
Underwater robotics is prevalent today in the field of undersea surveys. The current single-agent approach struggles to cover surveys of large areas, especially when visual analyses are ...required. Applications of underwater multi-robots fleets need to manage the coordination of the agents, which in turn stresses the already limited capabilities of underwater localization and communication. We propose a concept for a multilayered control architecture, which leverages visual recognition and swarm behavior to negotiate the coordination requirements of the single agent while retaining a significant level of control over the fleet of vehicles as a whole. This is obtained by including multiple control layers, paired with a heterogeneous composition of vehicles.
The cyclotides are the largest family of naturally occurring circular proteins. The mechanism by which the termini of these
gene-encoded proteins are linked seamlessly with a peptide bond to form a ...circular backbone is unknown. Here we report cyclotide-encoding
cDNA sequences from the plant Viola odorata and compare them with those from an evolutionarily distinct species, Oldenlandia affinis . Individual members of this multigene family encode one to three mature cyclotide domains. These domains are preceded by
N-terminal repeat regions (NTRs) that are conserved within a plant species but not between species. We have structurally characterized
peptides corresponding to these NTRs and show that, despite them having no sequence homology, they form a structurally conserved
α-helical motif. This structural conservation suggests a vital role for the NTR in the in vivo folding, processing, or detoxification of cyclotide domains from the precursor protein.
The new and promising field of soft robotics has many open areas of research such as the development of an exhaustive theoretical and methodological approach to dynamic modeling. To help contribute ...to this area of research, this paper develops a dynamic model of a continuum soft robot arm driven by cables and based upon a rigorous geometrically exact approach. The model fully investigates both dynamic interaction with a dense medium and the coupled tendon condition. The model was experimentally validated with satisfactory results, using a soft robot arm working prototype inspired by the octopus arm and capable of multibending. Experimental validation was performed for the octopus most characteristic movements: bending, reaching, and fetching. The present model can be used in the design phase as a dynamic simulation platform and to design the control strategy of a continuum robot arm moving in a dense medium.
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