Evolution of aerial spider webs coincided with repeated structural optimization of silk anchorages

Physical structures built by animals challenge our understanding of biological processes and inspire the development of smart materials and green architecture. It is thus indispensable to understand the drivers, constraints, and dynamics that lead to the emergence and modification of building behavior. Here, we demonstrate that spider web diversification repeatedly followed strikingly similar evolutionary trajectories, guided by physical constraints. We found that the evolution of suspended webs that intercept flying prey coincided with small changes in silk anchoring behavior with considerable effects on the robustness of web attachment. The use of nanofiber based capture threads (cribellate silk) conflicts with the behavioral enhancement of web attachment, and the repeated loss of this trait was frequently followed by physical improvements of web anchor structure. These findings suggest that the evolution of building behavior may be constrained by major physical traits limiting its role in rapid adaptation to a changing environment

Management of Dyslipidaemia in Real-world Clinical Practice: Rationale and Design of the VIPFARMA ISCP Project.

Dyslipidaemia plays a major role in the pathogenesis of atherosclerosis. Every year, scientific institutions publish cardiovascular prevention guidelines with updated goals and recommendations based on new evidence. However, medical barriers exist that make achieving these goals difficult and gaps between guidelines and best daily clinical practice still persist. The International Society of Cardiovascular Pharmacotherapy designed the Surveillance of Prescription Drugs in the Real World Project (VIPFARMA ISCP), a survey for physicians who manage lipid disorders in high-risk patients. Seven clusters of questions will be analysed comprising demographics, institution profile, access to continuing medical education, clinical practice profile, attitude regarding use of statins, knowledge regarding proprotein convertase subtilisin/kexin type 9 inhibitors and attitudes regarding medical decisions about triglycerides. The present study will be the first part of a larger programme and aims to shed light on barriers between lipid-lowering drug therapy recommendations in the 2019 European Society of Cardiology guidelines and clinical practice in different countries

A theoretical-numerical model for the peeling of elastic membranes

The adhesive behaviour of biological attachment structures such as spider web anchorages is usually studied using single or multiple peeling models involving "tapes", i.e. one-dimensional contacts elements. This is an oversimplification for many practical problems, since the actual delamination process requires the modelling of complex two-dimensional adhesive elements. To achieve this, we develop a numerical approach to simulate the detachment of an elastic membrane of finite size from a substrate, using a 3D cohesive law. The model is validated using existing analytical results for simple geometries, and then applied in a series of parametric studies. Results show how the pull-off force can be tuned or optimized by varying different geometrical or mechanical parameters in various loading scenarios, and the length of the detachment boundary, known as the peeling line, emerges as the key factor to maximize adhesion. The approach presented here can allow a better understanding of the mechanical behaviour of biological adhesives with complex geometries or with material anisotropies, highlighting the interaction between the stress distributions at the interface and in the membrane itself.Comment: 48 pages, 12 figure

A 3D Griffith peeling model to unify and generalize single and double peeling theories

It has been shown in recent years that many species in Nature employ hierarchy and contact splitting as a strategy to enhance the adhesive properties of their attachments. Maximizing the adhesive force is however not the only goal. Many animals can achieve a tunable adhesive force, which allows them to both strongly attach to a surface and easily detach when necessary. Here, we study the adhesive properties of 3D dendritic attachments, which are structures that are widely occurring in nature and which allow to achieve these goals. These structures exploit branching to provide high variability in the geometry, and thus tunability, and contact splitting, to increase the total peeling line and thus the adhesion force. By applying the same principles presented by A.A. Griffith 100 years ago, we derive an analytical model for the detachment forces as a function of their defining angles in 3D space, finding as limit cases 2D double peeling and 1D single peeling. We also develop a numerical model, including a nonlinear elastic constitutive law, for the validation of analytical calculations, allowing additionally to simulate the entire detachment phase, and discuss how geometrical variations influence the adhesive properties of the structure. Finally, we also realize a proof of concept experiment to further validate theoretical/numerical results. Overall, we show how this generalized attachment structure can achieve large variations in its adhesive and mechanical properties, exploiting variations of its geometrical parameters, and thus tunability. The in-depth study of similar basic structural units and their combination can in future lead to a better understanding of the mechanical properties of complex architectures found in Nature

Robust substrate anchorages of silk lines with extensible nano-fibres

Living systems are built of multiscale-composites: materials formed of components with different properties that are assembled in complex micro- and nano-structures. Such biological multiscale-composites often show outstanding physical properties that are unachieved by artificial materials. A major scientific goal is thus to understand the assembly processes and the relationship between structure and function in order to reproduce them in a new generation of biomimetic high-performance materials. Here, we tested how the assembly of spider silk nano-fibres (i.e. glue coated 0.5 μm thick fibres produced by so-called piriform glands) into different micro-structures correlates with mechanical performance by empirically and numerically exploring the mechanical behaviour of line anchors in an orb weaver, a hunting spider and two ancient web builders. We demonstrate that the anchors of orb weavers exhibit outstanding mechanical robustness with minimal material use by the indirect attachment of the silk line to the substrate through a soft domain ('bridge'). This principle can be used to design new artificial high-performance attachment systems

Fetal visceral maturation : a useful contribution to gestational age estimation in human fetuses.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=15461089International audienceWith regard to the law, estimating fetal age is essential to assess viability (after 20 weeks according to the WHO) and the proposed methods generally use long bone measurements. Here, we evaluated the accuracy of soft tissue maturational stage and compared it with long bone measurements. First, eight kinds of tissues or organs from 448 fetuses with known medical history were studied (macroscopically or histologically). We clearly demonstrated that adrenal glands and skin were very good age indicators, because some characteristics appeared only after 20 weeks. We established a linear regression with a 95% confidence interval of +/- 2.9 weeks. Second, we applied our original formula using femur measurement and we combined soft tissues and bones in a multiparametric regression. The confidence interval was reduced to +/- 2.5 weeks. We conclude that the pathologist must use both histological and anthropometric data to determine fetal age as accurately as possible