Academic literature on the topic 'Foldable segments'

AlphaFold2 (AF2) has created a breakthrough in biology by providing three-dimensional structure models for whole-proteome sequences, with unprecedented levels of accuracy. In addition, the AF2 pLDDT score, related to the model confidence, has been shown to provide a good measure of residue-wise disorder. Here, we combined AF2 predictions with pyHCA, a tool we previously developed to identify foldable segments and estimate their order/disorder ratio, from a single protein sequence. We focused our analysis on the AF2 predictions available for 21 reference proteomes (AFDB v1), in particular on their long foldable segments (>30 amino acids) that exhibit characteristics of soluble domains, as estimated by pyHCA. Among these segments, we provided a global analysis of those with very low pLDDT values along their entire length and compared their characteristics to those of segments with very high pLDDT values. We highlighted cases containing conditional order, as well as cases that could form well-folded structures but escape the AF2 prediction due to a shallow multiple sequence alignment and/or undocumented structure or fold. AF2 and pyHCA can therefore be advantageously combined to unravel cryptic structural features in whole proteomes and to refine predictions for different flavors of disorder.

Hybrid mobile robots with multiple locomotion modes are getting more and more popular in search and rescue (SAR) and explosive object disposal (EOD) missions because of their good terrain adaptability. Present researchers devote themselves to develop efficient and reliable transition method between different locomotion modes to make the hybrid robot more compact and flexible. In this paper, we present a novel transition mechanism for a hybrid wheel-track based on foldable rims. The wheel rim is cut into four segments so that it is foldable. And the transition between wheel and track is achieved by the folding or unfolding of the foldable rim. According to its geometrical property during the transition process, a single-freedom supporting spoke is proposed to drive the foldable rim’s transformation. We analyze the length and angle varying principles of the supporting spoke by utilizing the kinematic mode based on screw theory. According to above results, five different kinds of transition mechanism of the supporting spoke is designed, performance comparison among which is conducted by dynamic simulations. Two of the five candidate transition mechanisms are picked up for their smaller driving force requirements. Their 3D printing prototypes are also fabricated and experiments show that the hybrid wheel-track can switch between wheel and track successfully. Compared to most hybrid robots which have separate wheels, tracks and legs, this transition mechanism makes the robot own both compact structure and multimodal locomotion.

This article proposes a structural dynamics method for foldable stairs based on transfer matrix. The stairs are made up of a number of identical scissor-like elements which are supposed to be Euler–Bernoulli beams. The dynamics of each segment beam between every two adjacent revolute joints can be precisely expressed by the transfer matrix of the segment with the variables of boundary conditions of the joints. Therefore, the structural dynamics of the whole stairs is built using the least number of variables compared with the traditional methods. In addition, this method avoids the problem of the traditional transfer-matrix method that the number of variables greatly increases when there are a huge number of cross-joints within a structure.

Purpose To evaluate morphologic changes in the anterior segment using ultrasound biomicroscopic imaging (UBM) after phacoemulsification and foldable intraocular lens implantation (IOL). Methods Thirty-six patients with a mean age of 68.68 ± 8.44 years (range 51-89) who had phacoemulsification and foldable IOL implantation were included in this prospective study. Several anterior segment parameters including aqueous depth (AQD), trabecular meshwork-iris angle (TIA), ciliary body thickness (CBT), sclera thickness (ST), trabecular meshwork-ciliary process distance (T-CPD), iris-ciliary processes distance (I-CPD), and iris thickness (IT) were measured using UBM preoperatively and at postoperative month 2. Results There was a significant increase in AQD (p<0.001) and TIA (p<0.001) at postoperative month 2. However, CBT, ST, T-CPD, I-CPD, and IT did not significantly change (p>0.05) during the study period. Conclusions Removal of the crystalline lens results in change in the anterior segment parameters. Our results confirmed that UBM is a helpful option for the analysis of anterior segment structures both qualitatively and quantitatively.

This paper addresses some issues related to the deployability of a class of foldable parabolic reflectors. In particular, it is shown that, if global symmetry is maintained, the involved kinematic constraints require some of the foldable panels to pass kinematic bifurcation points in order for the deployment to complete. This constraint is pivotal in determining the deployment characteristics of parabolic and non-parabolic dishes alike. For parabolic reflectors of more than two panels per segment it is shown that the symmetric trapezoid shapes of the tessellations need to be relaxed to enable deployment.

Purpose To evaluate unexpected, acute intraocular anterior segment inflammation following uneventful cataract extraction by phacoemulsification and foldable posterior chamber intraocular lens (PCIOL) implantation. Methods This retrospective study evaluated five cases of postoperative inflammation that occurred after cataract extraction with foldable PCIOL implantation. Medical records were reviewed to analyze the unexplained postoperative inflammation. Results The five patients who developed inflammatory activity during the postoperative period responded well to corticosteroid treatment. Toxic maculopathy developed in one patient after aggressive antibacterial therapy. Vitrectomy was performed for one patient with prolonged vitreal inflammatory activity. Conclusions Noninfectious endophthalmitis developing upon surgery may be caused by a multifactorial process or an interindividual variable response to a common factor as a hypersensitivity reaction. It should be remembered in inflammatory cases after surgery in order to prevent the toxic, irreversible side effects of bacterial endophthalmitis treatment.

The case of a 29-year-old man is reported who presented with a gradually progressive, painless decrease in vision over 10 years. Anterior segment examination with a slit lamp revealed anterior lenticonus in both eyes. The patient had previously been diagnosed with bilateral sensorineural deafness, however investigations revealed microscopic haematuria and renal insufficiency that subsequently led to a diagnosis of classical Alport syndrome. Since the patient's quality of vision was severely affected by the bulging anterior lens capsule, surgical treatment was required. Clear lens phacoemulsification with continuous curvilinear capsulorhexis and foldable intraocular lens implantation were performed in each eye 2 days apart. One week after surgery, visual acuity was excellent in both eyes. Clear lens phacoemulsification with continuous curvilinear capsulorhexis and foldable intraocular lens implantation was a safe and effective therapeutic choice in this patient for the management of anterior lenticonus due to Alport syndrome.

Toxic anterior segment syndrome (TASS) developed in four cases after uneventful implantation of a foldable iris-fixated phakic intraocular lens (pIOL). Two cases occurred sequentially in one patient. The TASS subsided without complications in all cases after intensive topical steroid treatment. A multitude of possible causes is considered for the occurrence of these TASS cases. From the sterilization and cleaning of surgical instruments to the possibility of endotoxines in ophthalmic viscosurgical devices (OVD). These rare cases should alert the surgeon to the possibility of TASS after pIOL implantation.

This is a review of surgical options for posterior chamber intraocular lens (IOL) fixation in the absence of adequate capsular support. The indications, techniques, and outcomes for posterior chamber iris-sutured and scleral-fixated IOLs, including trans-scleral sutured and trans-scleral tunnel glued fixation, are reviewed. Iris-sutured IOL fixation may be appropriate in cases in which small corneal incisions with a foldable IOL are desired, but are only possible in cases of adequate iris tissue, and may be complicated by pupil ovaling and iris trauma, which can lead to prolonged inflammation in some studies. Scleral-sutured IOL fixation does not require robust iris tissue and decreases the risk for iris trauma, but is technically more demanding, may require larger incisions, and poses potentially more posterior segment complications. There are also ongoing concerns for suture exposure, erosion, and late suture breakage and IOL dislocation. Scleral tunnel-glued IOL fixation is a more recent innovation that avoids sutures and concerns for suture-related complications, and can be completed through smaller incisions with a foldable IOL. However, long-term studies are pending.

Une fraction significative des protéomes reste non annotée, laissant inaccessible une partie du répertoire fonctionnel de la vie, incluant des innovations moléculaires ayant une valeur thérapeutique ou environnementale. Le manque d'annotation fonctionnelle est en partie dû aux limites des approches actuelles pour la détection de relations cachées, ou à des caractéristiques spécifiques telles que le désordre. L'objectif de ma thèse a été de développer des approches méthodologiques reposant sur les signatures structurales des domaines repliés, afin de caractériser plus avant les séquences protéiques dont la fonction est inconnue, même en l'absence d'informations évolutives. Tout d'abord, j'ai développé un score permettant d'estimer le potentiel de repliement d'une séquence d'acides aminés, basé sur sa densité en amas hydrophobes, correspondant principalement aux structures secondaires régulières. J'ai décrit le continuum entre l'ordre et le désordre, couvrant différents états allant des conformations étendues aux globules fondus et ai caractérisé des cas d'ordre conditionnel. Ensuite, j'ai combiné ce score avec les prédictions de structure 3D d'AlphaFold2 (AF2) disponibles pour 21 protéomes de référence. Une grande fraction des acides aminés des modèles AF2 associés à un très faible index de confiance est incluse dans des segments non repliables, soutenant la qualité d'AF2 comme prédicteur du désordre. Cependant, dans chaque protéome, de longs segments repliables avec des prédictions AF2 de faible confiance présentent également des caractéristiques de domaines solubles et repliés. Cela suggère un ordre caché (conditionnel ou inconditionnel), qui n'est pas détecté par AF2 en raison du manque d'informations évolutives, ou des motifs de repliement non répertoriés. Enfin, à l'aide de ces outils, j'ai effectué une exploration préliminaire de protéines ou de régions non annotées, identifiées via le développement et l'application d'une nouvelle procédure d'annotation. Bien que ces séquences soient enrichies en désordre, une part importante d'entre elles présente des caractéristiques de type globulaire soluble. Ces séquences constituent de bons candidats pour de futures validations et caractérisations expérimentales. De plus, l'analyse de gènes de novo validés expérimentalement m'a permis de contribuer au débat encore ouvert sur les caractéristiques structurales des protéines codées par ces gènes, qui présentent un enrichissement en désordre et une grande diversité d'états structuraux
A significant fraction of the proteomes remains unannotated, leaving inaccessible a part of the functional repertoire of life, including molecular innovations with therapeutic or environmental value. Lack of functional annotation is partly due to the limitations of the current approaches in detecting hidden relationships, or to specific features such as disorder. The aim of my PhD thesis was to develop methodological approaches based on the structural signatures of folded domains, in order to further characterize the protein sequences with unknown function even in absence of evolutionary information. First, I developed a scoring system in order to estimate the foldability potential of an amino acid sequence, based on its density in hydrophobic clusters, which mainly correspond to regular secondary structures. I disentangled the continuum between order and disorder, covering various states from extended conformations (random coils) to molten globules and characterize cases of conditional order. Next, I combined this scoring system with the AlphaFold2 (AF2) 3D structure predictions available for 21 reference proteomes. A large fraction of the amino acids with very low AF2 model confidence are included in non-foldable segments, supporting the quality of AF2 as a predictor of disorder. However, within each proteome, long segments with very low AF2 model confidence also exhibit characteristics of soluble, folded domains. This suggests hidden order (conditional or unconditional), which is undetected by AF2 due to lack of evolutionary information, or unrecorded folding patterns. Finally, using these tools, I made a preliminary exploration of unannotated proteins or regions, identified through the development and application of a new annotation workflow. Even though these sequences are enriched in disorder, an important part of them showcases soluble globular-like characteristics. These would make good candidates for further experimental validation and characterization. Moreover, the analysis of experimentally validated de novo genes allowed me to contribute to the still-open debate on the structural features of proteins encoded by these genes, enriched in disorder and displaying a great diversity of structura

This study proposes and examines a novel approach to generate peristaltic locomotion gait in a segmented origami robot. Specifically, we demonstrate how to harness elastic multi-stability embedded in a soft origami skeleton to create an earthworm-like locomotion. Origami is attractive for building soft robots because it can exhibit the essential compliance and reduce the part count. Most importantly, it can work as an actuation mechanism. Moreover, embedding multi-stability into an origami skeleton allows it to remain in any of the stable states and switch between different states via a series of jumps. In this paper, we use two serially connected bistable Kresling segments, each featuring a generalized crease pattern design and a foldable anchoring mechanism, to develop a driving module for crawling soft robot. Multi-stability analysis of this dual-segment module reveals a four-phase actuation cycle, which is then used to generate the peristaltic gait. Instead of controlling the segment deformations individually like in earthworm and other crawling robots; we only control the total length of our driving module. This approach can significantly reduce the total number of actuators needed for locomotion and simplify the control requirements. The purpose of this paper is to combine the best features of multi-stable mechanisms and origami to advance the state of art of earthworm inspired crawling soft robot. Our results demonstrate the potential of using multi-stable origami mechanisms to generate locomotion gaits without the need of complex controllers.

This study presents a Ritz-type analysis for obtaining the vibration frequencies and mode shapes of beams that have a discontinuity in slope. Such structures have a wide range of applications in engineering as they often represent structural idealizations of complex structures such as robotic arms, crack modeling and foldable wings of aircraft. In the present study, the beams have been modeled using Euler Bernoulli’s theory, and the discontinuity in slope is represented by a torsional spring connecting the two segments of the beam. The beams are discretized into subdomains based on the location of the discontinuity. Legendre polynomials are used to define the displacement variation over individual uniform domains. The continuity of displacement is applied at the interface of adjacent subdomains and is enforced into the global system of equations using a condensation procedure. This procedure eliminates the dependent Ritz constant obtained from the displacement continuity. This study focuses on obtaining the vibration frequencies and mode shapes of a simply-supported beam with a discontinuity in slope and compares the results with the analytical solution. The paper would be of interest to researchers involved with the structural health monitoring of beams with cracks, robotic arms, and vibrations of folding wings like the one being considered for 777-X.

Abstract The exploration of new lands has always been a source of motivation for mankind. Despite the common idea that our planet is fully known, a huge number of inaccessible places still remains unvisited today, especially below the surface. Recent advances in robotics allow some of these locations to be explored by unmanned vehicles. This paper presents the design of a 3-modules lighter-than-air vehicle specifically conceived to autonomously explore inaccessible caves and underground environments. The design is inspired from an arthropod, scutigera coleoptrata, a long-legged centipede commonly found in our houses. Instead of crawling on walls like its biological counterpart, the robotic scutigera hovers and flies in cave tunnels. The aim is to develop a flexible semi-rigid, segmented airship that can withstand long, smooth explorations of caves while transmitting in real-time the images and sounds that it captures. To develop the model of the system, the kinematics of the modules are obtained in the inertial frame, and the dynamic derivation of the vehicle is obtained using Kane’s equations, which can also be extended for an n-bodies system. Its motion is illustrated with a couple of simplified scenarios in the horizontal plane and only having actuation in the front, or first module, of the airship. A structural design of the modules is presented and supported with a proof-of-concept prototype.

In this paper, we present a kinematic theory for Hoberman and other similar foldable linkages. By recognizing that the building blocks of such linkages can be modeled as planar linkages, different classes of possible solutions are systematically obtained including some novel arrangements. Criteria for foldability are arrived by analyzing the algebraic locus of the coupler curve of a PRRP linkage. They help explain generalized Hoberman and other mechanisms reported in the literature. New properties of such mechanisms including the extent of foldability, shape-preservation of the inner and outer profiles, multi-segmented assemblies and heterogeneous circumferential arrangements are derived. The design equations derived here make the conception of even complex planar radially foldable mechanisms systematic and easy. Representative examples are presented to illustrate the usage of the design equations and the kinematic theory.