57 research outputs found
Substrate thermal properties influence ventral brightness evolution in ectotherms
The thermal environment can affect the evolution of morpho-behavioral adaptations of ectotherms. Heat is transferred from substrates to organisms by conduction and reflected radiation. Because brightness influences the degree of heat absorption, substrates could affect the evolution of integumentary optical properties. Here, we show that vipers (Squamata:Viperidae) inhabiting hot, highly radiative and superficially conductive substrates have evolved bright ventra for efficient heat transfer. We analyzed the brightness of 4161 publicly available images from 126 species, and we found that substrate type, alongside latitude and body mass, strongly influences ventral brightness. Substrate type also significantly affects dorsal brightness, but this is associated with different selective forces: activity-pattern and altitude. Ancestral estimation analysis suggests that the ancestral ventral condition was likely moderately bright and, following divergence events, some species convergently increased their brightness. Vipers diversified during the Miocene and the enhancement of ventral brightness may have facilitated the exploitation of arid grounds. We provide evidence that integument brightness can impact the behavioral ecology of ectotherms. Jonathan Goldenberg et al. use photographic data and ancestral state reconstruction of 126 viper species to show that substrate type influences the evolution of ventral brightness for efficient heat transfer. Their results suggest that these patterns may have been involved in the diversification of vipers during the Miocene, and highlight the importance of ventral body regions when considering behavioral ecology and evolution.</p
Modeling Structural Colors from Disordered One-Component Colloidal Nanoparticle-based Supraballs using Combined Experimental and Simulation Techniques
Bright, saturated structural colors in birds have inspired synthesis of
self-assembled, disordered arrays of assembled nanoparticles with varied
particle spacings and refractive indices. However, predicting colors of
assembled nanoparticles, and thereby guiding their synthesis, remains
challenging due to the effects of multiple scattering and strong absorption.
Here, we use a computational approach to first reconstruct the nanoparticles'
assembled structures from small-angle scattering measurements and then input
the reconstructed structures to a finite-difference time-domain method to
predict their color and reflectance. This computational approach is
successfully validated by comparing its predictions against experimentally
measured reflectance and provides a pathway for reverse engineering colloidal
assemblies with desired optical and photothermal properties.Comment: 14 pages, 3 figures, 1 ToC figur
Structural Color Production in Melanin-based Disordered Colloidal Nanoparticle Assemblies in Spherical Confinement
Melanin is a ubiquitous natural pigment that exhibits broadband absorption
and high refractive index. Despite its widespread use in structural color
production, how the absorbing material, melanin, affects the generated color is
unknown. Using a combined molecular dynamics and finite-difference time-domain
computational approach, this paper investigates structural color generation in
one-component melanin nanoparticle-based supra-assemblies (called supraballs)
as well as binary mixtures of melanin and silica (non-absorbing)
nanoparticle-based supraballs. Experimentally produced one-component melanin
and one-component silica supraballs, with thoroughly characterized primary
particle characteristics using neutron scattering, produce reflectance profiles
similar to the computational analogues, confirming that the computational
approach correctly simulates both absorption and multiple scattering from the
self-assembled nanoparticles. These combined approaches demonstrate that
melanin's broadband absorption increases the primary reflectance peak
wavelength, increases saturation, and decreases lightness factor. In addition,
the dispersity of nanoparticle size more strongly influences the optical
properties of supraballs than packing fraction, as evidenced by production of a
larger range of colors when size dispersity is varied versus packing fraction.
For binary melanin and silica supraballs, the chemistry-based stratification
allows for more diverse color generation and finer saturation tuning than does
the degree of mixing/demixing between the two chemistries.Comment: 40 pages, Figure
Mechanism of Structural Colors in Binary Mixtures of Nanoparticle-based Supraballs
Inspired by structural colors in avian species, various synthetic strategies
have been developed to produce non-iridescent, saturated colors using
nanoparticle assemblies. Mixtures of nanoparticles varying in particle
chemistry (or complex refractive indices) and particle size have additional
emergent properties that impact the color produced. For such complex
multi-component systems, an understanding of assembled structure along with a
robust optical modeling tool can empower scientists to perform intensive
structure-color relationship studies and fabricate designer materials with
tailored color. Here, we demonstrate how we can reconstruct the assembled
structure from small-angle scattering measurements using the computational
reverse-engineering analysis for scattering experiments (CREASE) method and
then use the reconstructed structure in finite-difference time-domain (FDTD)
calculations to predict color. We successfully, quantitatively predict
experimentally observed color in mixtures containing strongly absorbing melanin
nanoparticles and demonstrate the influence of a single layer of segregated
nanoparticles on color produced. The versatile computational approach presented
in this work is useful for engineering synthetic materials with desired colors
without laborious trial and error experiments.Comment: 23 Pages, 5 Figures, 1 ToC Figur
Применение метода контрольных возмущений для определения характерных узлов присоединения комплексной нагрузки при расчетах динамической устойчивости
Рассматривается влияние способа замещения комплексной нагрузки на характер электромеханических переходных процессов в электрических системах (ЭС) от действия больших возмущений. Показано, что установить общие рекомендации относительно способа замещения нагрузки в сложных ЭС затруднительно. Предлагается для определения характерных узлов нагрузки, оказывающих существенное влияние на характер динамического перехода, применять известный метод контрольных возмущений. Приводятся результаты сравнительных расчетов с использованием предлагаемой методики
Spiders do not escape reproductive manipulations by Wolbachia
<p>Abstract</p> <p>Background</p> <p>Maternally inherited bacteria that reside obligatorily or facultatively in arthropods can increase their prevalence in the population by altering their hosts' reproduction. Such reproductive manipulations have been reported from the major arthropod groups such as insects (in particular hymenopterans, butterflies, dipterans and beetles), crustaceans (isopods) and mites. Despite the observation that endosymbiont bacteria are frequently encountered in spiders and that the sex ratio of particular spider species is strongly female biased, a direct relationship between bacterial infection and sex ratio variation has not yet been demonstrated for this arthropod order.</p> <p>Results</p> <p>Females of the dwarf spider <it>Oedothorax gibbosus </it>exhibit considerable variation in the sex ratio of their clutches and were infected with at least three different endosymbiont bacteria capable of altering host reproduction i.e. <it>Wolbachia</it>, <it>Rickettsia </it>and <it>Cardinium</it>. Breeding experiments show that sex ratio variation in this species is primarily maternally inherited and that removal of the bacteria by antibiotics restores an unbiased sex ratio. Moreover, clutches of females infected with <it>Wolbachia </it>were significantly female biased while uninfected females showed an even sex ratio. As female biased clutches were of significantly smaller size compared to non-distorted clutches, killing of male embryos appears to be the most likely manipulative effect.</p> <p>Conclusions</p> <p>This represents to our knowledge the first direct evidence that endosymbiont bacteria, and in particular <it>Wolbachia</it>, might induce sex ratio variation in spiders. These findings are pivotal to further understand the diversity of reproductive phenotypes observed in this arthropod order.</p
The role of knowledge about user behaviour in demand response management of domestic hot water usage
The relationship between workplace climate, motivation and learning approaches for knowledge workers
Substrate thermal properties influence ventral brightness evolution in ectotherms
Jonathan Goldenberg et al. use photographic data and ancestral state reconstruction of 126 viper species to show that substrate type influences the evolution of ventral brightness for efficient heat transfer. Their results suggest that these patterns may have been involved in the diversification of vipers during the Miocene, and highlight the importance of ventral body regions when considering behavioral ecology and evolution
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