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We examined morphological differences in cranium size and shape between closely related snake species, Natrix natrix and Natrix tessellata (Natricinae, Colubroidea), as well as variation within species. These two snake species have similar ecology and habitat preferences but differ in feeding strategies. Our hypothesis was that divergence in size and shape of cranial elements between species depends on their functional role and anatomical relationships. To analyse complex, kinetic crania, we applied computed microtomography and 3D geometric morphometrics. We analysed size and shape of six cranial elements separately. We selected two 'non-trophic' structures (akinetic braincase and mobile nasals) and four movable 'trophic' skeletal elements (maxillae, quadrates, pterygoids and compound bones) which are involved in prey capture and swallowing. Our results showed that N. natrix and N. tessellata significantly differ in size and shape of all analysed cranial elements. In both species, cranium is significantly larger in females than in males. To account for possible differences in shape due to differences in size, we estimated allometric and non-allometric component of shape variation. For all elements, except nasals, allometry accounted for a significant proportion of the variance in shape. The analysis of non-allometric component of shape variation revealed significant dimorphism in shape of the braincase and maxilla between N. tessellata females and males, and marginally significant sexual dimorphism in shape of maxilla in N. natrix. These results indicated that sexual dimorphism in skull shape is species specific and not entirely caused by selection for larger size in females. [ABSTRACT FROM AUTHOR]

The circuit-level simulation analysis of the single event transient response of an on-chip single event latchup protection switch (SPS cell), previously designed and developed in the IHP 250 nm CMOS process, is presented. The SPS cell provides the latchup protection for standard cells on the principle of power domain control. It is based on a sensing/driving PMOS transistor which acts both as a latchup sensor and a driver for the standard cells, and includes additional PMOS and NMOS transistors for controlling the sensing/driving transistor and interfacing to the external control logic. The previous work has confirmed the SPS cell's functionality in the case of single event latchup, and the experimental investigation has proven that the SPS cell is immune to single event latchup for LET values up to 74.8 MeV∙cm/mg. This case study extends the previous research by introducing the circuit-level simulation of the SPS cell's response to the single event transients (SETs). Using the square pulse current as a SET model, the amplitude and duration of the SET-induced voltage pulses at the SPS cell's outputs have been analyzed with respect to the injected charge, operating temperature, supply voltage, load (number of standard cells connected to the SPS cell) and sensing/driving transistor's channel width. The results have shown that the immunity of the SPS cell to SETs can be significantly enhanced by connecting a larger number of standard cells to the SPS cell and increasing the sensing/driving transistor's size, without any area overhead. An analytical expression for calculating the critical charge in terms of the transistor size and the number of standard cells connected to the SPS cell has been derived. Moreover, the SPS cell can be used as a SET sensor for detecting the levels of injected charge which cannot be mitigated by the increase of transistor size and load, and in conjunction with the external control logic it could be possible to measure the SET duration and perform online corrections of the SET-induced faults in the standard cells supplied by the SPS cell. [ABSTRACT FROM AUTHOR]

Dense vegetation cover undoubtedly offers certain advantages for small and slow-moving animals, but its disadvantages concerning some aspects of spatial ecology (e.g. movements) were neglected in previous studies. Tortoises could get stuck in vegetation by protuberant part of the shell and thus succumb to overheating, dehydration or predators. To examine how vegetation cover shapes behavioural responses of 'trapped' tortoises, we tested adults of six populations from habitats with contrasting vegetation cover. The tortoises were fitted with a non-stretchable rope, representing a piece of vegetation, stuck on the protruding front part of the plastron. Results suggested the existence of two distinct releasing techniques. First, and only successful in this study, is frequent changing of the movement direction, with a minimal pulling force, until the obstacle detached. The other involved the maximal pulling force aimed at ripping out the constraint. Tortoises from shrub habitats had more releasing success, used less pulling force and needed shorter time period to release, contrary to tortoises from herbaceous habitats. Although sexes showed similar releasing success, females obtained lower number of direction changes and higher yanking force compared to males, suggesting slightly different liberating strategies between the sexes. For immobilized tortoises without suitable shelter from overheating and dehydration, appropriate behavioural response could be vital, especially during drought years, due to increased physiological stresses. Variability of behavioural patterns among tortoise populations, described in this study, could have an adaptive significance. [ABSTRACT FROM AUTHOR]