1,721,326 research outputs found
Multispectral satellite imaging improves detection of large individual fossils
Full text linkPalaeontological field surveys in remote regions are a challenge, because of uncertainty in finding new specimens, high transportation costs, risks for the crew and a long time commitment. The effort can be facilitated by using high-resolution satellite imagery. Here we present a new opportunity to investigate remote fossil localities in detail, mapping the optical signature of individual fossils. We explain a practical workflow for detecting fossils using remote-sensing platforms and cluster algorithms. We tested the method within the Petrified Forest National Park, where fossil logs are sparse in a large area with mixed lithologies. We ran both unsupervised and supervised classifications, obtaining the best estimations for the presence of fossil logs using the likelihood and spectral angle mapper algorithms. We recognized general constraints and described logical and physical pros and cons of each estimated map. We also explained how the outcomes should be critically evaluated with consistent accuracy tests. Instead of searching for fossiliferous outcrops, our method targets single fossil specimens (or highly condensed accumulations), obtaining a significant increase in potential efficiency and effectiveness of field surveys. When repeatedly applied to the same region over time, it could also be useful for monitoring palaeontological heritage localities. Most importantly, the method here described is feasible, easily applicable to both fossil logs and bones, and represents a step towards standard best practices for applying remote sensing in the palaeontological field
An explorative study of peculiar cue of relative distance in perceptual folding.
No full textABSTRACT: This work is a widening of findings concerning a peculiar case of amodal completion, the completion by folding. It occurs when four quadrilaterals look like a rectangular sheet of paper folded around an interposed rectangle, even when there are not the conditions for a geometric folding (Massironi & Bressanelli, 2002). In this work a simple geometric measure, the lateral separation between the left and right visible parts of the strip, was considered as a possible cue to distance, that is, the measure might be a cue to separation in depth between the two parts of the strip. Two experiments were conducted in order to verify the presence of perceived depth separation between the two parts of the strip and the role of the different lateral separations on the depth perception. In experiment 1 we used an indirect measure of depth: the size constancy effect. In experiment 2 we directly rated the apparent separation in depth between the two parts of the folded strip. Results lent support to the experimental hypothesis
A reliable indicator of female fecundity: the case of the yellow belly in Knipowitschia panizzae (Teleostei: Gobiidae)
No full textA large body of research has developed on
male ornaments and their role in sexual selection while
female ornaments have been less investigated. This
study focused on the presence, function, and possible
role of a sexually dimorphic nuptial trait as an indicator
of female quality in a fish species presenting
‘‘conventional’’ sex roles: the yellow patch on the belly
of Knipowitschia panizzae females. Aquarium spawning
experiments demonstrated that this ornament is due to
dermal pigments, is displayed only when the female is
ready to spawn, and is switched off within minutes
from the end of egg deposition. This sexual trait is
variable in size among females and indicates female
fecundity relative to her own body size. As a consequence,
female yellow belly appears to be a reliable
indicator of female quality as measured by current
fecundity. Field data on natural nests highlights that
males usually perform parental care on only one egg
batch at a time. The modality of egg deposition suggests
that males may be limited in their potential
reproductive rates by environmental factors. Male
limitations in egg care could favour male choosiness
and the evolution of female nuptial displays
Yellow belly as honest signal of female quality in Knipowitschia panizzae (Gobiidae)
No full textSexually dimorphic traits are common in fish species, and examples from both males
and females have been described. The function of these traits has been widely investigated
in males. On the contrary, female ornaments have been studied mainly in sex role
reversed species, such as pipefish, while their role in species with ‘conventional’ sex
roles remain to be investigated.
This study focused on the presence, function, and possible role as indicator of female
quality of a sexually dimorphic nuptial trait in the lagoon goby, Knipowitschia panizzae.
In this species, that present conventional sex roles, females show a yellow spot on the
belly. Aquarium spawning experiments demonstrated that the coloration on the belly is
due to dermal pigments, is displayed only when female is ready to spawn and is switched
off within few minutes from the end of egg deposition. This sexual trait presents
variability in size among females and indicates female fecundity relatively to her own
body size. As a consequence, female yellow belly appears to be an honest signal of female
quality. Field data on natural nests highlighted that males perform parental cares mostly
only on one egg batch at a time and the modality of egg deposition suggested that males
are limited in their potential reproductive rates by environmental factors. Male limitation
in egg care could constitute the basis for a female biased operational sex ratio, favouring
male choosiness and the evolution of female nuptial displays
A new cue to distance in a case of amodal completion
No full textABSTRACT: We studied a well-defined set of line drawings that we call `completion by folding'. Such completion occurs when four quadrilaterals are arranged in such a way that two of them (called visible tails) look like a sheet of paper folded around an interposed rectangle. This is a type of amodal completion with unification which is produced even when current models do not foresee such a perceptual solution.We advance the hypothesis that such amodal completion depends on a 3-D interpretation. That is, the interposed rectangle may be seen as a parallelepiped. This hypothesis can account for those figures where the amodal unification occurs without the classical amodal completion constraints. In two experiments, we investigated the possibility that the geometrical horizontal distance between the two visible tails could be a new cue to relative distance. In experiment 1 we used the size-constancy effect to test the plausibility of the 3-D hypothesis. In experiment 2 we investigated the effect of the distances between the two tails on the degree of perceived depth. Experiment 1 confirmed the presence of the perceived depth, while results from experiment 2 confirmed a direct dependence of perceived depth on the physical distances of the two tails
La piegatura di parallelogrammi: una ricerca sperimentale in condizioni statiche e dinamiche.
No full text- …
