Ultraviolet Reflectance Research Articles

Partial replacement of B-site cation to stabilize the optically active cubic phase of FAPbI3 for optoelectronic applications

Due to the unique and indispensable electronic, physical and chemical properties, halide perovskites are being widely used in optoelectronic applications like solar cells and LEDs. However, the stability of halide perovskites has always been an alarming issue towards the development of these devices on an industrial scale. Specifically, Formamidinium Lead Iodide (FAPbI3), the most suitable organic halide perovskite for solar cells is very unstable due to environmental factors like humidity, temperature and ultraviolet radiation which led to poor-performing devices. Moreover, FAPbI3 is more stable in its photo-inactive hexagonal (δ-FAPbI3) phase. For photovoltaic devices, only the optically active cubic phase (α-FAPbI3) is suitable due to its proper band gap (∼1.45 eV). In this communication, we have partially substituted the Pb2+ cation in FAPbI3 with Tin (Sn2+) and Manganese (Mn2+). The structural and optical properties are analyzed using X-Ray Diffraction, Ultra-violet Diffuse Reflectance Spectroscopy and Photoluminescence (PL) spectroscopy. The results show that the α-FAPbI3 phase can be retained with successful incorporation of Sn2+ and Mn2+ at the B-site of FAPbI3 structure.

Citrus sinensis and Musa acuminata Peel Waste Extract Mediated Synthesis of TiO2/rGO Nanocomposites for Photocatalytic Degradation of Methylene Blue under Visible Light Irradiation.

Water pollution caused by various natural and artificial sources such as expansion of industrialization, rapid increment in population size, the threat of climate change, and development in urbanization takes a serious attention. Due to this fact, various protocols and techniques were adopted for the treatment of such polluted water. In the present findings, TiO2 nanoparticles (NPs) and TiO2/rGO nanocomposites (NCs) were synthesized using titanium tetra butoxide in the presence of Citrus sinensis (CS) and Musa acuminata (MA) peel waste extract as a capping, reducing, and stabilizing agent. The synthesized NPs and NCs were characterized using thermogravimetric-differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) pattern, ultraviolet diffuse reflectance spectroscopy (UV-DRS), and Fourier transform infrared (FTIR) spectroscopy. The synthesized NPs and NCs were investigated as green alternative photocatalyst for the degradation of methylene blue (MB) dye under visible light irradiation. Thermal analysis results confirmed that the green synthesized TiO2 NPs were found to be too stable above 550°C. XRD analysis result showed that the average crystalline size of CS and MA mediated synthesized TiO2 NPs with various volume ratios was in the range of 7.3–27.3 nm and 13.4–22.4 nm, respectively. The average crystalline size of CS and MA peel extract template synthesized TiO2/rGO NCs was found to be in the range of 7.5–15.3 and 11.2–12.5 nm, respectively. The band gap energy was calculated to be in the range of 3.17–3.29 eV and 3.10–3.38 eV for the CS and MA mediated synthesized TiO2 NPs, respectively. Eg of CS and MA peel extract template formed TiO2/rGO NCs was found to be in the range of 2.85–3.11 eV and 3.07–3.11 eV, respectively. SEM analysis proved that the various synthesized TiO2 NPs and TiO2/rGO NCs were spherical in shape and the absence of any other foreign materials confirmed the purity of the corresponding nanocatalysts. In addition, TEM, HRTEM, and SAED analysis confirmed that the structures of the synthesized nanocatalysts were spherical in shape and the catalysts were too crystalline and the result was found to fit with the XRD result. Among the synthesized various volume ratios of TiO2 nanocatalysts, high percentage of degradation (62% and 58.2%) was achieved using TiO2-2c and TiO2-2 m, respectively. Moreover, 94.28% and 94.25% of MB degradation were achieved in the presence of TiO2/rGO-1.5c and TiO2/rGO-1.5c nanocomposite photocatalysts, respectively.

A Comprehensive Study on the Synthesis and Characterization of TiO2 Nanoparticles Using Aloe vera Plant Extract and Their Photocatalytic Activity against MB Dye

This paper investigates the use of A. vera extract as a natural capping agent for TiO2 nanoparticles as well as a reducing agent for TiO2 nanoparticles. XRD, ultraviolet diffuse reflectance (UV-DRS), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDXA) were used to characterize the material. In their X-ray diffraction patterns, the titanium dioxide nanoparticles were found to have a high degree of crystallinity, indicating that they were synthesized. Infrared (FT-IR) spectra were used to determine the chemical composition of the plant extract. The DRS spectra in the UV-visible range reveal a high absorption peak at 356 nm, which indicates the existence of TiO2 nanoparticles in the sample. Shape of nanoparticles was revealed by SEM and TEM morphological investigations, which revealed their irregular and somewhat spherical nature. Only titanium and oxygen compounds were found in the EDX spectrum, indicating that they were present. This demonstrates that the NPs that were produced are devoid of contaminants. Using the produced nanoparticles as catalyst, we presented a photocatalytic degradation method for the dye methylene blue in this paper. The findings showed that 94 percent of the damage occurred within 120 minutes of being exposed to UV radiation.

Remarkable enhancement of the TiO2 photocatalyst activity under visible light by doping sulfur for dye photodecolorization

To enhance the photoactivity of TiO2 under visible light, doping TiO2 by sulfur atoms from sulfuric acid has been conducted by hydrothermal method, where the concentration of the acid is varied (25, 50, and 100 mmol/L) to obtain the doped TiO2-S with various S content. The doped photocatalysts obtained are characterized by using X-ray diffraction, ultraviolet specular reflectance spectrophotometer, Fourier transform infrared, and transmission electron microscope machines. The activity of the doped photocatalyst has been examined for Congo-red photo-decolorization under visible light, via batch experiment. The research results assigned that the doping sulfur into TiO2 has successfully narrowed the gap that resulted in the remarkable enhancement of the activity under visible light in the Congo red decolorization. The enhancement is influenced by S content in the photocatalyst and the highest activity is shown by TiO2-S prepared from 50 mmol/L sulfuric acids. The efficiency of the Congo-red photo-decolorization catalyzed by TiO2-S (50) is found to be controlled by reaction time, photocatalyst weight, and solution pH. By applying 50 mg of the photocatalyst weight in 50 mL of the dye solution with pH 7, within 60 min, the highest photo-decolorization of 10 mg/L Congo-red, that is 87% could be reached.

Assessment of crystallographic and electronic phase stability of shock wave loaded cubic cerium oxide nanoparticles

Rapid progress has been documented during the last couple of years in understanding the crystallographic structural features of a few functional materials that have been achieved under dynamic shock wave loaded conditions. In this context, we report the crystallographic and electronic phase stability of shock wave loaded Cerium oxide nano-crystalline (CeO 2 NPs) material and the results have been evaluated by X-ray diffraction (XRD), Raman spectroscopy and ultra-violet diffuse reflectance spectroscopy (UV-DRS). XRD and Raman spectroscopic results show that the title material doesn't undergo any crystallographic phase transitions. UV-DRS spectral results demonstrate that the Ce 4+ ionic state is not affected by the impact of shock waves. The obtained FE-SEM micrographs provide the substantiation for the stability of the sample. Based on the observed results, the title material can be suggested for the making of medical glassware, spaceship windows and technological applications of coating.

Sending private messages: Floral ultraviolet signals are correlated with pollination syndromes in Erica

The presence of ultraviolet (UV, wavelengths between 300-400 nm) reflectance in insect-pollinated flowers has been linked to pollination efficiency and pollination shifts, but little is known about its prevalence and function in other pollination systems and African species. We chose the genus Erica for studying the prevalence of UV because of its extreme radiation (c. 680 species) in the Cape, South Africa, with a diversity of pollination syndromes. This study quantified the prevalence and brightness of UV reflectance for five Erica pollination syndromes and tested pollinator preferences for UV reflectance in the two groups with the highest prevalence: sunbirds and long-proboscid flies. Our results show that UV colouration is absent or rare in Erica species pollinated by unclassified insects, rodents or wind. About 17 % of bird-pollinated species reflected UV but choice experiments revealed that free-ranging sunbirds showed no preference for UV signals. All sampled long-proboscid fly-pollinated species reflected UV and its experimental removal decreased seed set drastically, suggesting that long-proboscid flies in the Cape strongly prefer or depend on UV and thereby contributed to selecting for the evolution of this signal.

Vacuum ultraviolet high-reflectance aluminum mirrors on copper substrate for application in noble liquid time projection chamber

Enhancing vacuum ultraviolet reflection at surface of Cu electrode is key to obtain sufficient photon collection efficiency in noble liquid time projection chamber. In this work, MgF2-overcoated Al mirrors is utilized to realize the desired high reflectivity for scintillation photons of liquid xenon at 175 nm. Thermal evaporation technique is explored for the mirror preparation. The Al mirror deposited directly on Cu substrate suffers from severely absorptive and scattering losses and yields 30.3% reflectivity due to the formation of Cu–Al alloy. By prior deposition of a SiO2 intermediate layer on the Cu substrate, the alloy process is prevented and the absorptive loss is suppressed by a factor of 4 approximately. The highest reflectance 82.1% is obtained through optimizing the thickness of the SiO2 intermediate layer. The work holds potential to improve the capability of noble liquid time projection chambers for detection of dark matter and neutrinoless double beta decays.

Sunscreens effectiveness are not altered by concomitant use of moisturizing creams: An ultraviolet reflectance photography study.

Sunscreens are widely used to protect the skin against the harmful effects of solar radiation. It is not known whether solar protection factor of a sunscreen is altered by the concomitant use of other cosmetic products. The aim of this study was to analyze changes in the protective effect of different commercial and ISO standards sunscreens with high SPF applied shortly before and after application of non-sunscreens galenic formulas type moisturizing creams. ISO 24444:2019 standard sunscreens, which claimed SPF 16 and 63, as well as 4 different claimed SPF 50 and 50+ commercial sunscreens were prepared and applied in different sequential order to the back of 25 volunteers and compared with different commercial moisturizing formulas. Ultraviolet (UV) reflectance photography followed by image analysis was used to compare untreated skin and skin treated with moisturizing creams alone and combined with sunscreens. The UV reflectance analysis showed no significant changes of the skin color reflectance treated with moisturizing cream compared with untreated skin. Application of the sunscreen formulations were associated with a 35% - 70% decrease in color related to the in vivo expected SPF, indicating significant UV absorption for all sunscreen formulas. All standard and commercial sunscreens showed no significant differences in UV reflection color level when combined with the different moisturizing creams applied before or after the sunscreen. Effectiveness of low- and high-protection sunscreens were not altered by the concomitant use of a moisturizing creams applied shortly before and after the sunscreens.

Within-plant Distributions and Density of Amblyseius swirskii (Acari: Phytoseiidae) as Influenced by Interactions Between Plastic Mulch and Vegetable Crop Species

Plastic mulch of different colors and ultraviolet (UV) reflectivity individually or combined with released arthropod predators is an important component of an integrated pest management strategy. In 2015 and 2016, we evaluated the density and within-plant distribution of a released predatory mite, Amblyseius swirskii Athius-Henriot (Acari: Phytoseiidae) in snap bean (Phaseolus vulgaris L.), cucumber (Cucumis sativus L.), yellow squash (Cucurbita pepo L.), eggplant (Solanum melongena L.), Jalapeno pepper (Capsicum annuum L.), and tomato (Solanum lycopersicum L.) grown on different plastic mulches. The mulch treatments evaluated were: metalized top and black bottom, metalized top and white bottom, black-on-black, black-on-white, white-on-black, and bare soil with no mulch. Crop species had a significant effect on the density of A. swirskii. Eggplant and cucumber had higher numbers of A. swirskii than the other crops tested in 2015. In 2016, the density of A. swirskii was higher on eggplant than on cucumber. There was a variation in the distribution of A. swirskii in different strata of the plant canopies with the highest number in the bottom stratum of each crop, which was positively correlated with the population of Thrips palmi Karny (Thysanoptera: Thripidae). Mulch type had no effect on the density or distribution of A. swirskii in any strata of any of the crops tested. The results of this study indicate that releasing A. swirskii is compatible with the use of UV-reflective mulch. This information about host preference and within-plant distribution of A. swirskii should be of value in pest management programs for the crops studied.

Synthesis of visible light activated metal-organic framework coated on titania nanocomposite (MIL-53(Al)@TiO2) and dye photodegradation

Herein, MIL-53(Al)@TiO2 photocatalyst with high photocatalytic performance in the presence of visible light was favorably fabricated using a solvothermal method. Characterization of MIL-53(Al)@TiO2 was carried out by Fourier transform infrared (FTIR), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), the ultraviolet visible diffused reflectance spectra (DRS), and energy-dispersive X-ray (EDX) analyses, and its photocatalytic activity for the degradation of methylene blue (MB) dye was investigated. Compared with MIL-53(Al) and TiO2, the photocatalytic activity of MIL-53(Al)@TiO2 composite under visible light irradiation was improved. This improvement is attributed to the strategy used in composite synthesis without blocked of any hole by TiO2 nanoparticles. The synthesized MIL-53(Al)@TiO2 nanocomposite degraded 95% of the MB in 240 ​min without any electron acceptor, while the decolorization of dye by MIL-53(Al) and TiO2 was 51% and 79%, respectively. The data also indicated that the dye degradation by MIL-53(Al)@TiO2 followed first-order kinetic with high correlation coefficient (0.9927).

Enhancing the sweat resistance of sunscreens.

While sunbathing of performing outdoor sport activities, sunscreens are important for protection of uncovered skin against ultraviolet (UV) radiation. However, perspiration negatively affects the performance of a sunscreen film by weakening its substantivity and uniformity through the activation of two mechanisms, namely sunscreen wash-off and sunscreen redistribution. We used a perspiring skin simulator to investigate the effect of sunscreen formulation on its efficiency upon sweating. Specifically, we modified the sunscreen formulation by incorporating a hydrophobic film former and adding water-absorbing particles. Sunscreen performance before and after perspiration is assessed by in vitro sun protection factor measurements, direct detection of changes in the sunscreen distribution using UV reflectance imaging, and by coherent anti-Stokes Raman scattering (CARS) microscopy for microscopic characterization of the UV filter relocation. The results show that incorporating a hydrophobic film former can decrease sunscreen wash-off due to sweating, while an excessive amount of film former might negatively affect the sunscreen distribution. The addition of water-absorbing particles, on the other hand, had either a negative or positive impact on the sunscreen substantivity, depending on the particle properties. While the addition of large water-absorbing particles appeared to increase sunscreen redistribution, smaller particles that could form a gel-like structure upon contact with water, appeared to change sunscreen wetting and sweat droplet spreading, thereby decreasing sunscreen wash-off and sunscreen redistribution. We find that using a combination of hydrophobic film formers, which increase water resistance, and small water-absorbing particles, which change the wetting behavior, can make sunscreen formulations more sweat-resistant and less runny.

Effect of ITO Content on Properties of Functional Graphene Coating on Cotton Fabric

In order to investigate the effect of indium tin oxide (ITO) on the performance of graphene functional coating on cotton fabric, different contents of ITO were added to the graphene coating system, and the effects of ITO content and curing time on various properties of graphene coating were studied. The results showed that the ITO particles adsorbed on the graphene sheets and filled the gaps between the graphene sheets, forming a dense conductive network, which could further improve the conductive performance of the functional coatings. When ITO content was 1.2%, the resistivity of the coating reached the lowest 1.8 Ω·cm, and the overall ultraviolet transmittance and reflectance were the lowest. With the increase of ITO content, the infrared reflectance will first decrease and then slowly increase, but the infrared reflectance is all below 0.5%. When the curing time reached 90 s, the resistivity and UV transmittance of cotton fabric coating decreased. With the extension of curing time, the coating on infrared reflectivity gradually increased, but the infrared reflectivity of the overall < 1%.

Avian visual ecologists should consider UV absorbance and all sensory modalities: A response to Wisenden et al. (2020)

In a recent publication, Wisenden et al. (2020) examined responses of territorial male Red-winged Blackbirds (Agelaius phoeniceus) to models constructed with ultraviolet (UV)-reflective red epaulets for the purpose of determining if the addition of UV reflectance to epaulets (“UV+”) changed the effectiveness of signals to receivers relative to “control” epaulets under field conditions. The authors hypothesized that “UV+epaulet coloration represents a visual signal with increased efficacy in territorial interactions.” They presented behavioral data but no visual modeling data. Our aims in this commentary are to suggest alternative terms to those used by the authors, to express concern about the use of sunscreen to manipulate the UV condition of surfaces, and to make a plea for additional data collection in future studies of avian visual ecology. The terms UV+ and UV– should be reserved for studies that create environments free from UV radiation for comparison with environments that include UV radiation. We believe that commercial sunscreens are not an appropriate choice for altering the UV conditions of surfaces presented during behavioral trials because they potentially introduce confounding influences from other sensory inputs or irritation of peripheral nerves. Wisenden et al. altered the UV absorbance of their sunscreen-treated models but did not present absorbance spectra and may not have collected those data. We acknowledge that the lack of absorbance spectra is not unusual. We implore any such future studies to collect absorbance spectra of treated and control surfaces so that those data may be used to improve visual models for UV-sensitive animals.

Investigation of structural, morphological, and optoelectronic properties of Ga-doped TiO2 nanoparticles for electron transport layer in solar cell applications: An experimental and theoretical study

In the current work, the sol-gel synthesis method was used to synthesize both undoped and gallium (1%-Ga) doped TiO2 nanoparticles. The as-deposited materials were calcined at 400–500 °C with a temperature variation rate of 5 °C per minute. The crystallographic properties of the semiconductor materials were determined from X-ray diffraction (XRD) which showed the formation of anatase TiO2. The average crystallite sizes, determined from the widths of the XRD reflections, were 11 and 4 nm for undoped and Ga-doped TiO2, respectively. The materials were further studied by density functional theory with meta-generalized gradient approximation exchange–correlation functional. Supercell systems consisting of 24 and 48 atoms were created to form 12.5% and 6.25% Ga dopant substitution, respectively. These structures were optimized to obtain the ground state properties. Transmission electron microscopy showed polycrystalline, spherical powders, with grain sizes comparable to those found using XRD. The surface morphology of the doped TiO2 obtained from scanning electron microscopy showed an improved surface structure compared to pristine TiO2. Moreover, the electronic states of the materials were investigated using X-ray photoelectron spectroscopy. Energy dispersive X-ray spectroscopy verified the elemental composition of titanium, oxygen, and Ga present in the nanoparticles. The surface chemical bonds were analyzed by Fourier-transform infrared spectroscopy. Ultraviolet diffused reflectance spectra analysis was used to examine their optical properties. The experimentally obtained bandgaps of pristine and 1% Ga-doped TiO2 nanoparticles were 2.9 and 3.09 eV, respectively. The optical properties were further analyzed by computing the band structures and density of states using density functional theory. Similar to the experimental results, these electronic structures showed an increase in bandgap after 6.25% Ga incorporation. However, with 12.5% doping, there was a decrement in the bandgap. The analysis showed that, with an appropriate amount of substitution, Ga-doped TiO2 semiconductor material can be used in the electron transport layer and many other fields of photoelectric cells.

Visible light photocatalytic degradation of organic dyes using W‐modified TiO2/SiO2 catalyst

AbstractIn the present study, the synthesis of W‐modified TiO2/SiO2 composite and its catalytic activity in the visible light region is demonstrated. The W‐modified TiO2/SiO2 composite was obtained from the hydrolysis of a mixture containing titanium (IV) oxysulfate, ammonium metatungstate, and SiO2 powder in an alkaline medium. The obtained materials were characterized by using X‐ray diffraction (XRD), Fourier transformation‐infrared spectroscopy (FT‐IR), high‐resolution transmission electron microscopy (HRTEM), energy dispersive X‐ray elemental mapping observation, nitrogen adsorption/desorption isotherms, photoluminescence spectra (PL), and ultraviolet visible diffusive reflectance spectroscopy (UV‐Vis DRS). In this material, W‐modified TiO2 nanoparticles of about 3‐5 nm were highly dispersed on the silica network. Both W‐modified TiO2 and W‐modified TiO2 decorated on the SiO2 substrate significantly promoted the visible light absorption of the material. The photocatalytic activity of the prepared catalyst was assessed through the photodegradation of Methylene blue, Rhodamine‐B, Methyl orange, and Congo red dyes under visible light illumination. It was found that the kinetic and equilibrium data of the photocatalytic process fitted the modified Langmuir‐Hinshelwood model well. Recyclable studies have shown that the catalyst still retained its original activity after the third cycle.

The influence of ultraviolet reflectance differs between conspicuous aposematic signals in neotropical butterflies and poison frogs.

Warning signals are often characterized by highly contrasting, distinctive, and memorable colors. Greater chromatic (hue) and achromatic (brightness) contrast have both been found to contribute to greater signal efficacy, making longwave colored signals (e.g., red and yellow), that are perceived by both chromatic and achromatic visual pathways, particularly common. Conversely, shortwave colors (e.g., blue and ultraviolet) do not contribute to luminance perception yet are also commonly found in warning signals. Our understanding of the role of UV in aposematic signals is currently incomplete as UV perception is not universal, and evidence for its utility is at best mixed. We used visual modeling to quantify how UV affects signal contrast in aposematic heliconiian butterflies and poison frogs both of which reflect UV wavelengths, occupy similar habitats, and share similar classes of predators. Previous work on butterflies has found that UV reflectance does not affect predation risk but is involved in mate choice. As the butterflies, but not the frogs, have UV‐sensitive vision, the function of UV reflectance in poison frogs is currently unknown. We found that despite showing up strongly in UV photographs, UV reflectance only appreciably affected visual contrast in the butterflies. As such, these results support the notion that although UV reflectance is associated with intraspecific communication in butterflies, it appears to be nonfunctional in frogs. Consequently, our data highlight that we should be careful when assigning a selection‐based benefit to the presence of UV reflectance.

Preparation of bimetal modified HMS molecular sieve and its desulfurization performance mechanism

AbstractIn this paper, dodecylamine (DDA) is used as the template, and ethyl orthosilicate (TEOS) is used as the silicon source. The HMS molecular sieve is prepared by in situ synthesis and modified by Cu, Ce, and Cu/Ce. The Cu/Ce‐HMS molecular sieve catalyst was synthesized for the first time. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and Fourier transform infrared spectrometer (FTIR) were used to characterize the synthesized composite molecular sieve. The results showed that the metal was loaded on the HMS intact and did not change the morphology of the HMS. A mixture of n‐hexane and dibenzothiophene (DBT) was used as the model oil, and the oxidation removal of DBT in the model oil was used as a probe reaction to study the photocatalytic oxidative desulfurization performance of the composite catalyst. The results show that the desulfurization rate after modification is Cu/Ce‐HMS molecular sieve &gt; Cu‐HMS molecular sieve &gt; Ce‐HMS. Finally, we explored the reaction mechanism of catalyst desulfurization. The results of ultraviolet diffuse reflectance showed that the modified molecular sieve Cu/Ce‐HMS had a smaller band gap, greater reaction activity, and stronger photocatalytic performance, which is benefit to improve the desulfurization efficiency. We report a simple and effective preparation method of composite molecular sieve catalyst, which provides a certain reference for future desulfurization research.

Chemical defense and tonic immobility in early life stages of the Harlequin cabbage bug, Murgantia histrionica (Heteroptera: Pentatomidae)

Antipredation strategies contribute to the lifetime reproductive success of organisms, particularly in more vulnerable life stages that look to survive until reproduction. In insects, eggs and larval stages are often immobile or unable to rapidly flee and hide from predators. Understanding what alternative antipredation strategies they use, but also how these change over development time, is required to fully appreciate how species adapt to biotic threats. Murgantia histrionica is a stink bug, conspicuously colored from egg to adult, known to sequester defensive glucosinolates from its cruciferous hosts as adults. We sought to assess whether this chemical defense is also present in its eggs and early nymphal instars and quantified how it fluctuates among life stages. In parallel, we looked at an alternative antipredation strategy, described for the first time in this species: tonic immobility (i.e., death feigning). We also qualitatively investigated ultraviolet reflectance in eggs and adults as a proxy of conspicuousness against UV-absorbing leaves. Our results show that the eggs are significantly more chemically defended than the first two but not third mobile life stages, yet compound concentrations do not statistically differ across nymphal instars. Tonic immobility is favored by hatchlings, but less so by subsequent instars. Eggs also had obvious ultraviolet reflectance, suggesting that they would contrast against a leaf substrate and, considering their chemical load, that they may be aposematic. We argue that there are two possible interpretations of our results. One is that, throughout ontogeny, tonic immobility is a useful defensive strategy until adequate chemical protection is achieved over an extended feeding period. The other is that both aposematism and tonic immobility are used by this species, but variation in strategy use throughout ontogeny is decoupled.

Silicon Nanotexture Surface Area Mapping Using Ultraviolet Reflectance

The enhanced surface area of silicon nanotexture is an important metric for solar cell integration as it affects multiple properties including optical reflectance, dopant diffusion, and surface recombination. Silicon nanotexture is typically characterized by its surface-area-to-projected-area ratio or enhanced area factor (EAF). However, traditional approaches for measuring EAF provide limited statistics, making correlation studies difficult. In this article, silicon's dominant ultraviolet reflectance peak, R(E2), which is very sensitive to surface etching, is applied to EAF spatial mapping. A clear decay correlation between R(E2) and EAF is shown for multiple textures created using reactive ion etching and metal catalyzed chemical etching. This correlation is applied to R(280 nm) reflectance mapping to yield accurate, high-resolution full-wafer EAF spatial mapping of silicon nanotextures. R(280 nm) mapping is also shown to be sensitive enough to correlate the impact of nanotexture spatial variation on post-diffusion sheet resistance. Finite-difference time-domain simulations of several nanoscale pyramid textures confirm a decay band for R(E2) versus EAF, consistent with our measurements. We suggest that R(E2) mapping may prove useful for other silicon nanotexture properties and applications where EAF is important.

Patterns of Visual and Ultraviolet Reflectance in Femoral Gland Secretions of Two Desert Lizards

Femoral gland secretions in lizards convey chemical information about the health and social status of the depositing individual. These secretions influence behaviors related to female mate choice and male–male competition, but little is known about how they are first located by lizards in the environment. Secretions are visually conspicuous and can be sighted from a distance by visually adept lizards, but the specificity of secretion reflectance to the depositing species remains unknown. We examined the reflectance spectra of femoral gland secretions from two sympatric lizard species, Aspidoscelis tigris and Gambelia wislizenii, to determine whether secretions could be visually distinguished. Mean reflectance did not differ between species, but A. tigris had higher reflectance in ultraviolet wavelengths. For both species, lizards in better body condition, as determined by the residuals of the relationship between snout–vent length and body mass, had higher ultraviolet reflectance. In summary, our results indicate that femoral gland secretions can be visually discriminated between species if the discriminating lizard is ultraviolet sensitive.