Near-ultraviolet chemiluminescence from the reaction of ammonia with hypobromite in aqueous solution

The chemiluminescence arising from the oxidation of ammonium chloride by sodium hypobromite in aqueous alkaline solution includes a series of peaks in the near-ultraviolet, which is not commonly observed in liquid-phase chemiluminescence. The dominant peak in that region has an intensity maximum at 292 nm and smaller peaks are observed at 313, 334 and 356 nm. The emitted photons are of similar energy to the Vergard–Kaplan transition of molecular nitrogen, a major product of this reaction. However, the spectral distribution is different to that of previously reported gas-phase chemiluminescence attributed to the Vergard–Kaplan transition.

Transmission electron microscopy characterization of the bake-hardening behavior of transformation-induced plasticity and dual-phase steels

The effect of prestraining (PS) and bake hardening (BH) on the microstructures and mechanical properties has been studied in transformation-induced plasticity (TRIP) and dual-phase (DP) steels after intercritical annealing. The DP steel showed an increase in the yield strength and the appearance of the upper and lower yield points after a single BH treatment as compared with the as-received condition, whereas the mechanical properties of the TRIP steel remained unchanged. This difference appears to be because of the formation of plastic deformation zones with high dislocation density around the “as-quenched” martensite in the DP steel, which allowed carbon to pin these dislocations, which, in turn, increased the yield strength. It was found for both steels that the BH behavior depends on the dislocation rearrangement in ferrite with the formation of cell, microbands, and shear band structures after PS. The strain-induced transformation of retained austenite to martensite in the TRIP steel contributes to the formation of a complex dislocation structure.

Time-resolved fluorescence microscopy of gunshot residue: an application to forensic science

Time-resolved fluorescence microscopy has rapidly emerged as the technique of choice for many researchers aiming to gain specific insights into the dynamics of intricate biological systems. Although the unique advantages the technique provides over other methods have proven to be particularly useful in the biosciences, to date they have been largely unexploited by other research disciplines. In this paper, we demonstrate the capacity of time-resolved fluorescence microscopy as a practical analytical tool in the forensic sciences via the imaging of gunshot residues that are expelled when a firearm is discharged. This information may prove to be useful for determination of the true sequence of events that took place in a firearm related crime.

Transmission electron microscopy investigation of substitution reactions from carbon nanotube template to silicon carbide nanowires

Substitution reactions between multiwalled carbon nanotubes and silicon monoxide vapour have been investigated using transmission electron microscopy. Different reactions occurred inside the multiwalled nanotubes and on the nanotube external surfaces, resulting in the formation of silicon carbide nanowires with a core–shell structure. The substitution reaction process and end products are strongly affected by nanotube structures and a ball milling treatment of the starting materials.

Reducing the photocatalytic activity of zinc oxide quantum dots by surface modification

The use of zinc oxide (ZnO) nanoparticles as ultraviolet (UV) absorbers for many organic substrates is limited because of the high photocatalytic activity of ZnO. In this study, a facile and efficient technique for the preparation of a hybrid material of silica-coated ZnO nanoparticles was used to reduce the photocatalytic activity of ZnO. Monodispersed ZnO nanopartcles were prepared by wet chemistry and the particle surface was modified by tetraethylorthosilicate to form a silica coating via the Sto¨ ber method. ZnO samples, both before and after the coating process, were investigated by transmission electron microscopy, X-ray diffraction, dynamic light scanning, infrared, and UV-Vis absorption spectroscopy. The effect of the surface modification on the photocatalytic activity of ZnO was studied by monitoring the degradation of Rhodamine B caused by photo-generated free radicals. The results implied that the photo-generation of free-radicals was strongly quenched by the presence of silica on the particle surface.

Ultraviolet vision in birds: what is its function?

Although UV vision was first demonstrated in birds in the early 1970s, its function is still unknown. Here we review the evidence for UV vision in birds, discuss the special properties of UV light, lay out in detail hypotheses for the function of UV vision in birds and discuss their plausibility. The main hypotheses are that UV vision functions: (i) in orientation, (ii) in foraging and (iii) in signalling. The first receives support from studies of homing pigeons, but it would be unwise to conclude that orientation is UV's primary function in all birds. It is especially important to test the signalling hypothesis because bird plumage often reflects UV and tests of theories of sexual selection have virtually always assumed that birds perceive plumage ''colours'' as humans do. A priori this assumption is unlikely to be correct, for unlike humans, birds see in the UV, have at least four types of cones and have a system of oil droplets which filters light entering individual cones.

Ultraviolet plumage colors predict mate preferences in starlings

Avian plumage has long been used to test theories of sexual selection, with humans assessing the colors, However, many birds see in the ultraviolet (<400 nm), to which humans are blind, Consequently, it is important to know whether natural variation in UV reflectance from plumage functions in sexual signaling, We show that female starlings rank males differently when UV wavelengths are present or absent, Principal component analysis of approximate to 1300 reflectance spectra (300-700 nm) taken from sexually dimorphic plumage regions of males predicted preference under the UV+ treatment. Under UV- conditions, females ranked males in a different and nonrandom order, but plumage reflectance in the human visible spectrum did not predict choice, Natural variation in UV reflectance is thus important in avian mate assessment, and the prevailing light environment can have profound effects on observed mating preferences.

Ultraviolet vision and mate choice in zebra finches

SEXUAL selection is one of the most actively studied areas of evolutionary biology(1-3), and ever since Darwin(1) birds have been probably the most popular taxon for testing the predictions about colour variation. Humans have been used to assess 'colour', an approach which may be flawed(4,5) as many birds see in the ultraviolet (to which humans are blind), and have at least four spectral classes of retinal cone cells (humans have only three), Here we report experiments on zebra finches which test the hypothesis that the ultraviolet waveband (300-400 nm) is used in avian mate-choice decisions. We found that the ultraviolet is used, and that it probably contributes to hue perception. This finding may have,vide implications for future studies of avian sexual selection and colour, and supports one hypothesized function of avian ultraviolet vision, the role of which is largely unknown.(4,6,7)

Egg colour matching in an African cuckoo, as revealed by ultraviolet-visible reflectance spectrophotometry

Despite major differences between human and avian colour vision, previous studies of cuckoo egg mimicry have used human colour vision (or standards based thereon) to assess colour matching. Using ultraviolet-visible reflectance spectrophotometry (300-700 nm), we measured museum collections of eggs of the red-chested cuckoo and its hosts. The first three principal components explained more than 99% of the variance in spectra, and measures of cuckoo-host egg similarity derived from these transformations were compared with measures of cuckoo-host egg similarity estimated by human observers unaware of the hypotheses we were testing. Monte Carlo methods were used to simulate laying of cuckoo eggs at random in nests. Results showed that host and cuckoo eggs were very highly matched for an ultraviolet versus greenness component, which was not detected by humans. Furthermore, whereas cuckoo and host were dissimilar in achromatic brightness, humans did not detect this difference. Our study thus reveals aspects of cuckoo-host egg colour matching which have hitherto not been described. These results suggest subtleties and complexities in the evolution of host-cuckoo egg mimicry that were not previously suspected. Our results also have the potential to explain the longstanding paradox that some host species accept cuckoo eggs that are non-mimetic to the human eye.

Ultraviolet cues affect the foraging behaviour of blue tits

The function of avian ultraviolet (UV) vision is only just beginning to be understood. One plausible hypothesis is that UV vision enhances the foraging ability of birds. To test this, we carried out behavioural experiments using wild-caught blue tits foraging for cabbage moth and winter moth caterpillars on natural and artificial backgrounds. The light environment in our experiments was manipulated using either UV-blocking or UV-transmitting filters. We found that the blue tits tended to find the first prey item (out of four) more quickly when UV cues were present. This suggests that UV vision offers benefits to birds when searching for cryptic prey despite the prey and backgrounds reflecting relatively little UV Although there was no direct effect of UV on the time taken to find all four prey items in a trial, search performance in the absence of UV wavelengths tended to increase over the course of an experiment. This may reflect changes in the search tactics of the birds. To our knowledge, these are the first data to suggest that birds use UV cues to detect cryptic insect prey and have implications for our understanding of protective coloration.

Blue tits are ultraviolet tits

The blue tit (Parus caeruleus) has been classified as sexually monochromatic. This classification is based on human colour perception yet, unlike humans, most birds have four spectrally distinct classes of cone and are visually sensitive to wavelengths in the near-ultraviolet (300-400 nm). Reflectance spectrophotometry reveals that blue tit plumage shows considerable reflection of UV light. For example, the blue crest shows peak reflectance at wavelengths around 352 nm. Furthermore, the blue tit is sexually dichromatic for multiple regions of plumage, including the crest. Choice trials performed in the laboratory indicate that females prefer males with the brightest crests. This study has implications for both intra-and interspecific studies of sexual selection, as well as future classification of dichromatism, which should not ignore the possibility of variation in reflectance in the UV.