Insect exoskeleton (cuticle) has a broad range of mechanical properties depending on the function of a particular structure of the skeleton. Structure and mechanical properties of the specialised cuticle of insect joints remain largely unknown to date. We used scanning (SEM) and transmission electron microscopy (TEM) to obtain information about the material structure of the gula plate, the head part of the head-to-neck articulation system in the beetle Pachnoda marginata. The surface of this cuticle appears rather smooth in SEM. The fibers of the exocuticle are partly oriented almost perpendicular to the surface, which is rather unusual for arthropod cuticle. Nanoindentation experiments were performed to determine the local mechanical properties (hardness and elastic modulus) of the gula material. To understand the effect of desiccation and the influence of an outer wax layer on the mechanical behavior of the material, the samples were tested in fresh, dry and chemically treated (lipid extraction in organic solvents) conditions. Nanoindentation results were found to be strongly influenced by desiccation but only slightly by lipid extraction. Decreasing water content ( approximately 15-20% of the cuticle mass) led to an increase in hardness (from 0.1 to 0.49 GPa) and elastic modulus (from 1.5 to 7.5 GPa). The lipid extraction caused a slight further hardening (to 0.52 GPa) as well as stiffening (to 7.7 GPa) of the material. The results are discussed in relation to the mechanical function of the gula plate.
We propose a probabilistic Monte Carlo
Approach to the distributed modeling of shallow rainfall-induced landslides.
For the purpose, we have modified the TRIGRS code. The new code (TRIGRS-P)
Adopts a stochastic approach to compute, on a cell-by-cell basis, transient
Pore-pressure changes and related...
We study a problem where a group of agents has to decide how a joint reward
Should be shared among them. We focus on settings where the share that each
Agent receives depends on the subjective opinions of its peers concerning that
Agent's contribution to the group. To this end, we introduce a mechan...
While observations in the radio band are providing essential information on
the innermost structures of relativistic jets in active galactic nuclei (AGN),
the recent detection by Fermi of gamma-ray emission from many hundreds of
blazars shows that the maximum jet power is emitted at high energies....
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