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Forensic Sciences Research 2021Signature examination is the most common examination performed by any document examiner. Determination of the authenticity of a handwritten signature on a questioned...
Signature examination is the most common examination performed by any document examiner. Determination of the authenticity of a handwritten signature on a questioned document is an important task for forensic document examiners in the forensic science field. As a result of continuous developments in technology, a signature stamp can now be created using a photosensitive seal to enable the reproduction of a handwritten signature. These stamps are commonly used in China and several other countries. In this study, 10 types of black photosensitive stamp-pad ink, 10 brands of fountain pen ink, 15 types of black gel ink and six types of black erasable gel ink found on the Chinese domestic market were collected and 10 photosensitive signature stamps were created using the signatures of 10 people. Microscopic analysis, infrared (IR) and fluorescence analyses and microspectrophotometry (MSP) techniques were used to examine the resulting photosensitive signature stamp impressions when applied to printing papers, writing papers and invoice papers. By comparing the printing and spectral characteristics of the photosensitive signature stamp impressions with those of the signatures executed using the fountain pens, gel pens and erasable gel pens, it was possible to determine whether each signature was written or stamped using a photosensitive signature stamp. To validate these results, a 96.7% absolute accuracy and a 99.3% detection rate were achieved over a total of 150 blind tests conducted by five forensic document examiners, thus demonstrating that a combination of the four analysis methods used in this work can provide a more scientific approach and improve the accuracy and the detection rate of the examination process.KEY POINTSA signature stamp is a photosensitive seal made in the style of a handwritten signature.Although microscopic analysis can usually provide better examination results, a comprehensive examination method that includes microscopic analysis and ink composition analysis is required to improve the accuracy and the detection rate of the examination process.This study collected and tested photosensitive stamp-pad inks, fountain pen inks, gel inks and erasable inks.Infrared and fluorescence analyses and microspectrophotometry were able to distinguish the photosensitive ink from both erasable ink and fountain pen ink. Supplemental data for this article are available online at https://doi.org/10.1080/20961790.2021.1898755.
PubMed: 34377575
DOI: 10.1080/20961790.2021.1898755 -
Scientific Reports May 2022Fishes often have cone photoreceptors organized in lattice-like mosaic formations. In flatfishes, these lattices undergo dramatic changes during metamorphosis whereby a...
Fishes often have cone photoreceptors organized in lattice-like mosaic formations. In flatfishes, these lattices undergo dramatic changes during metamorphosis whereby a honeycomb mosaic of single cones in the larva is replaced by a square mosaic of single and double cones in the adult. The spatio-temporal dynamics of this transition are not well understood. Here, we describe the photoreceptors and mosaic formations that occur during the larva to juvenile transition of Atlantic halibut from the beginning of eye migration to its completion. To gauge the possibility of colour vision, visual pigments in juveniles were measured by microspectrophotometry and the opsin repertoire explored using bioinformatics. At the start of eye migration, the larva had a heterogeneous retina with honeycomb mosaic in the dorsonasal and ventrotemporal quadrants and a square mosaic in the ventronasal and dorsotemporal quadrants. By the end of metamorphosis, the square mosaic was present throughout the retina except in a centrodorsotemporal area where single, double and triple cones occurred randomly. Six cone visual pigments were found with maximum absorbance (λ, in nm) in the short [S(431) and S(457)], middle [M(500), M(514) and M(527)], and long [L(550)] wavelengths, and a rod visual pigment with λ at 491 nm. These pigments only partially matched the opsin repertoire detected by query of the Atlantic halibut genome. We conclude that the Atlantic halibut undergoes a complex re-organization of photoreceptors at metamorphosis resulting in a multi-mosaic retina adapted for a demersal life style.
Topics: Animals; Flatfishes; Flounder; Larva; Opsins; Retinal Cone Photoreceptor Cells; Retinal Pigments; Rod Opsins
PubMed: 35577858
DOI: 10.1038/s41598-022-11998-9 -
Polymers Jan 2022Bamboo is a natural fibre reinforced composite with excellent performance which is, to a certain extent, an alternative to the shortage of wood resources. The...
Bamboo is a natural fibre reinforced composite with excellent performance which is, to a certain extent, an alternative to the shortage of wood resources. The heterogeneous distribution and molecular structure of lignin is one of the factors that determines its performance, and it is the key and most difficult component in the basic research into the chemistry of bamboo and in bamboo processing and utilization. In this study, the distribution of lignin components and lignin content in micro-morphological regions were measured in semi-quantitative level by age and radial location by means of visible-light microspectrophotometry (VLMS) coupled with the Wiesner and Maule reaction. There as guaiacyl lignin and syringyl lignin in the cell wall of the fibre. Lignin content of the secondary cell wall and cell corner increased at about 10 days, reached a maximum at 1 year, and then decreased gradually. From 17 days to 4 years, the lignin content of the secondary cell wall in the outer part of bamboo is higher than that in the middle part (which is, in turn, higher than that in the inner part of the bamboo). VLSM results of the micro-morphological regions showed that bamboo lignification developed by aging. Guaiacyl and syringl lignin units can be found in the cell wall of the fibre, parenchyma, and vessel. There was a difference in lignin content among different ages, different radial location, and different micro-morphological regions of the cell wall. The fibre walls were rich in guaiacyl lignin in the early stage of lignification and rich in syringyl units in the later stage of lignification. The guaiacyl and syringyl lignin deposition of bamboo green was earlier than that of the middle part of bamboo culm, and that of the middle part of bamboo culm was earlier than that of bamboo yellow. The single molecule lignin content of the thin layer is higher than that of thick layers, while the primary wall is higher than the secondary cell wall, showing that lignin deposition is consistent with the rules of cell wall formation. The obtained cytological information is helpful to understand the origin of the anisotropic, physical, mechanical, chemical, and machining properties of bamboo.
PubMed: 35054725
DOI: 10.3390/polym14020312 -
Journal of the Royal Society, Interface Oct 2019Insect colour is extremely diverse and produced by a large number of pigmentary and nanostructural mechanisms. Considerable research has been dedicated to these optical...
Insect colour is extremely diverse and produced by a large number of pigmentary and nanostructural mechanisms. Considerable research has been dedicated to these optical mechanisms, with most of it focused on chromatic colours, such as blues and greens, and less on achromatic colours like white and gold. Moreover, studies on the evolution of these colours are less common and largely limited to inferences from extant organisms, in part because of the limited amount and types of available fossil material. Here, we directly compare nanostructure and colour of extant and amber-preserved (approx. 15 and 99 Myr old, respectively) gold-coloured representatives of micromoths (Lepidoptera: Micropterigidae) and springtails (Collembola: Tomoceridae). Using electron microscopy, microspectrophotometry and finite domain time difference optical modelling, we show that golden coloration in the extant micromoth is produced by nanometre-scale crossribs that function as zero-order diffraction gratings and in the springtail by a diffraction grating without crossribs. Surprisingly, nanostructure and thus predicted colour of the amber-preserved specimens were nearly identical to those of their extant counterparts. Removal of amber enabled direct colour measurement of the fossil micromoth and further revealed that its colour matched both that of the extant specimen and the predicted colour, providing further support for our optical models. Our data thus clearly show an early origin and striking conservation of scale nanostructures and golden coloration, suggesting strong selection pressure either on the colour itself or on the mechanisms that produce the colour. Furthermore, we show the thus-far untapped potential for the use of amber-preserved specimens in studies on the evolution of organismal coloration.
Topics: Animals; Arthropods; Biological Evolution; Fossils; Pigmentation
PubMed: 31575346
DOI: 10.1098/rsif.2019.0366 -
The Journal of Experimental Biology Dec 2019Nature's nanostructures can bring about vivid and iridescent colours seen in many insects, notably in beetles and butterflies. While the intense structural colours can...
Nature's nanostructures can bring about vivid and iridescent colours seen in many insects, notably in beetles and butterflies. While the intense structural colours can be advantageous for display purposes, they may also be appealing to predators and therefore constitute an evolutionary disadvantage. Animals often employ absorption and scattering in order to reduce the directionality of the reflected light and thereby enhance their camouflage. Here, we investigated the monkey beetle using microspectrophotometry, electron microscopy, fluorimetry and optical modelling. We show that the dull green dorsal colour comes from the nanostructured scales on the elytra. The nanostructure consists of a multi-layered photonic structure covered by a filamentous layer. The filamentous layer acts as a spatial diffuser of the specular reflection from the multilayer and suppresses the iridescence. This combination leads to a colour-stable and angle-independent green reflection that probably enhances the camouflage of the beetles in their natural habitat.
Topics: Animals; Coleoptera; Color; Female; Fluorometry; Male; Microscopy, Electron, Scanning; Microspectrophotometry; Models, Biological
PubMed: 31767735
DOI: 10.1242/jeb.213306 -
Journal of the Royal Society, Interface May 2022While the specific mechanisms of colour production in biological systems are diverse, the mechanics of colour production are straightforward and universal. Colour is...
While the specific mechanisms of colour production in biological systems are diverse, the mechanics of colour production are straightforward and universal. Colour is produced through the selective absorption of light by pigments, the scattering of light by nanostructures or a combination of both. When copepods were fed a carotenoid-limited diet of yeast, their orange-red body coloration became faint, but their eyespots remained unexpectedly bright red. Raman spectroscopy indicated a clear signature of the red carotenoid pigment astaxanthin in eyespots; however, refractive index matching experiments showed that eyespot colour disappeared when placed in ethyl cinnamate, suggesting a structural origin for the red coloration. We used transmission electron microscopy to identify consecutive nanolayers of spherical air pockets that, when modelled as a single thin film layer, possess the correct periodicity to coherently scatter red light. We then performed microspectrophotometry to quantify eyespot coloration and confirmed a distinct colour difference between the eyespot and the body. The observed spectral reflectance from the eyespot matched the reflectance predicted from our models when considering the additional absorption by astaxanthin. Together, this evidence suggests the persistence of red eyespots in copepods is the result of a combination of structural and pigmentary coloration.
Topics: Animals; Carotenoids; Copepoda; Microscopy, Electron, Transmission; Organelles; Pigmentation
PubMed: 35611618
DOI: 10.1098/rsif.2022.0169 -
Journal of Comparative Physiology. A,... Jan 2020Retinas of the river lamprey Lampetra fluviatilis were studied by microspectrophotometry, electroretinography and single-photoreceptor electrophysiology to reconcile the...
Retinas of the river lamprey Lampetra fluviatilis were studied by microspectrophotometry, electroretinography and single-photoreceptor electrophysiology to reconcile the apparently contradictory conclusions on the nature of lamprey photoreceptor cells drawn in the early work by Govardovskii and Lychakov (J Comp Physiology A 154:279-286, 1984) and in recent studies. In agreement with recent works, we confirmed former identification of short photoreceptors as rods and of long photoreceptors as cones. In line with the results of 1984, we show that within a certain range of light intensities the lamprey retina exhibits "color discrimination". We found that the overlap of working intensity ranges of rods and cones is not a unique feature of lamprey short receptors, and suggest that rod-cone (possibly color) vision may be common among vertebrates. We show that the decay of meta-intermediates in lamprey cones occurs almost 100 times faster than in typical rod metarhodopsins. Rate of decay of metarhodopsins of lamprey rods take an intermediate position between typical rods and cones. This makes lamprey rhodopsin similar to transmuted cone visual pigment in "rods" of nocturnal geckos. We argue that defining various types of photoreceptors as simply "rods" and "cones" may be functionally correct, but neglects their genetic, biochemical and morphological features and evolutionary history.
Topics: Animals; Biological Evolution; Color Vision; Electroretinography; Lampreys; Retinal Cone Photoreceptor Cells; Retinal Pigments; Retinal Rod Photoreceptor Cells; Rhodopsin
PubMed: 31942647
DOI: 10.1007/s00359-019-01395-5 -
BMC Biology Jun 2022Differences in morphology, ecology, and behavior through ontogeny can result in opposing selective pressures at different life stages. Most animals, however, transition...
BACKGROUND
Differences in morphology, ecology, and behavior through ontogeny can result in opposing selective pressures at different life stages. Most animals, however, transition through two or more distinct phenotypic phases, which is hypothesized to allow each life stage to adapt more freely to its ecological niche. How this applies to sensory systems, and in particular how sensory systems adapt across life stages at the molecular level, is not well understood. Here, we used whole-eye transcriptomes to investigate differences in gene expression between tadpole and juvenile southern leopard frogs (Lithobates sphenocephalus), which rely on vision in aquatic and terrestrial light environments, respectively. Because visual physiology changes with light levels, we also tested the effect of light and dark exposure.
RESULTS
We found 42% of genes were differentially expressed in the eyes of tadpoles versus juveniles and 5% for light/dark exposure. Analyses targeting a curated subset of visual genes revealed significant differential expression of genes that control aspects of visual function and development, including spectral sensitivity and lens composition. Finally, microspectrophotometry of photoreceptors confirmed shifts in spectral sensitivity predicted by the expression results, consistent with adaptation to distinct light environments.
CONCLUSIONS
Overall, we identified extensive expression-level differences in the eyes of tadpoles and juveniles related to observed morphological and physiological changes through metamorphosis and corresponding adaptive shifts to improve vision in the distinct aquatic and terrestrial light environments these frogs inhabit during their life cycle. More broadly, these results suggest that decoupling of gene expression can mediate the opposing selection pressures experienced by organisms with complex life cycles that inhabit different environmental conditions throughout ontogeny.
Topics: Animals; Anura; Larva; Life Cycle Stages; Metamorphosis, Biological; Rana pipiens; Transcriptome
PubMed: 35761245
DOI: 10.1186/s12915-022-01341-z -
The Journal of Experimental Biology Apr 2024In many animals, ultraviolet (UV) vision guides navigation, foraging, and communication, but few studies have addressed the contribution of UV signals to colour vision,...
In many animals, ultraviolet (UV) vision guides navigation, foraging, and communication, but few studies have addressed the contribution of UV signals to colour vision, or measured UV discrimination thresholds using behavioural experiments. Here, we tested UV colour vision in an anemonefish (Amphiprion ocellaris) using a five-channel (RGB-V-UV) LED display. We first determined that the maximal sensitivity of the A. ocellaris UV cone was ∼386 nm using microspectrophotometry. Three additional cone spectral sensitivities had maxima at ∼497, 515 and ∼535 nm. We then behaviourally measured colour discrimination thresholds by training anemonefish to distinguish a coloured target pixel from grey distractor pixels of varying intensity. Thresholds were calculated for nine sets of colours with and without UV signals. Using a tetrachromatic vision model, we found that anemonefish were better (i.e. discrimination thresholds were lower) at discriminating colours when target pixels had higher UV chromatic contrast. These colours caused a greater stimulation of the UV cone relative to other cone types. These findings imply that a UV component of colour signals and cues improves their detectability, which likely increases the prominence of anemonefish body patterns for communication and the silhouette of zooplankton prey.
Topics: Animals; Color; Color Vision; Retinal Cone Photoreceptor Cells; Color Perception; Perciformes; Ultraviolet Rays
PubMed: 38586934
DOI: 10.1242/jeb.247425 -
Scientific Reports Jan 2020Coloration in insects provides a fruitful opportunity for interdisciplinary research involving both physics and biology, and for a better understanding of the design...
Coloration in insects provides a fruitful opportunity for interdisciplinary research involving both physics and biology, and for a better understanding of the design principles of biological structures. In this research we used nanometric and micrometric analyses to investigate the morphological and mechanical properties of the black-orange-black (BOB) color pattern in scelionid wasps, which has never been studied. The primary objective of the present investigation was to explore the structural and mechanical differences in the mesoscutum of four species: Baryconus with an orange mesosoma (i.e. BOB pattern), all black Baryconus, Scelio with an orange mesosoma (i.e. BOB pattern), and all black Scelio. The most outstanding findings include the absence of multilayer structures that generate structural color, a pigment concentrated in the upper surface of the epicuticle, and surprising differences between the four species. Three of the four species showed an accordion-like structure in the furrow (notaulus), whereas the adjacent mesoscutum was different in each species. Moreover, the normalized color component spectra for blue, green and red colors of the black mesoscutum of each genus showed the same spectral dependence while the orange color manifested small changes in the dominant wavelength, resulting in slightly different orange tones.
Topics: Animals; Biotechnology; Color; Interdisciplinary Communication; Microscopy, Electron, Scanning; Microspectrophotometry; Nanotechnology; Optics and Photonics; Wasps
PubMed: 31996729
DOI: 10.1038/s41598-020-58301-2