Grazing-incidence iridescence from a butterfly wing

Copyright © 2002 Optical Society of America. This paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-41-3-437. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.The Troides magellanus butterfly exhibits a specialized iridescence that is visible only when its hind wings are both illuminated and viewed at near-grazing incidence. The effect is due to the presence of a constrained bigrating structure in its wing scales that has been previously observed in only one other species of butterfly (Ancyluris meliboeus). However, whereas the Ancyluris presents wide-angle flickering iridescence, the Troides butterfly uses pigmentary coloration at all but a narrow tailored range of angles, producing a characteristic effect

War crimes prosecution – lessons learned from Bosnia and Herzegovina

Since the war ended fifteen years ago, war crimes prosecution has been the dominant tool of addressing war crimes committed during the four-year-long conflict in Bosnia and Herzegovina (1992-1995). The prosecution has been conducted at the International Criminal Tribunal for the former Yugoslavia (ICTY), the national institutions (Court of BiH, Sarajevo) and the local courts (cantonal and district in Republika Srpska, the Federation of BiH and the Brcko District – all entities established as a result of the Dayton Peace Accords). All these institutions have been criticized by various individuals in different capacities, for different reasons – some of these will be discussed in the proposed paper. The paper will also address the effectiveness of war crimes prosecution in all these institutions as a tool for combating future crimes, taking into account the accomplishments and shortcomings of the effort at all levels – international, national and local. Another important question is if war crimes prosecution can be done in combination with other complementary mechanisms to minimize the potential for future conflicts. The ICTY and the courts in BiH have conducted numerous trials in the past fifteen years; hundreds have been investigated and prosecuted but the question remains, can war crimes prosecutions, when conducted fairly and timely be an investment into the country’s future and if so what can be done to secure proper prosecution in similar situations. In that sense, this paper will be focusing on policy measures and lessons learned from the Bosnian experience. The author spent three years living in Bosnia and Herzegovina, working in war crimes prosecution and therefore, the paper will draw heavily on personal experience as an analyst in the Special War Crimes Department of the Prosecutor’s office in Sarajevo. It will also take into account the more recent experiences from the ICTY in The Hague as well as academic sources on the issue

Light manipulation principles in biological photonic systems

© 2013 Science Wise Publishing and DE GRUYTER.The science of light and colour manipulation continues to generate interest across a range of disciplines, from mainstream biology, across multiple physicsbased fields, to optical engineering. Furthermore, the study of light production and manipulation is of significant value to a variety of industrial processes and commercial products. Among the several key methods by which colour is produced in the biological world, this review sets out to describe, in some detail, the specifics of the method involving photonics in animal and plant systems; namely, the mechanism commonly referred to as structural colour generation. Not only has this theme been a very rapidly growing area of physics-based interest, but also it is increasingly clear that the biological world is filled with highly evolved structural designs by which light and colour strongly influence behaviours and ecological functions.We acknowledge the financial support of DARPA contract W911NF-10-C-0069 and of AFOSR grant FA9550-10-1-0020. We also wish to thank Caroline Pouya, Helen Ghiradella, Radislav Potyrailo, Roy Sambles, Shuichi Kinoshita and Doekele Stavenga for helpful discussions

Book Review Some Kind of Justice: The ICTY\u27s Impact in Bosnia and Serbia

In December 2017, the International Criminal Tribunal for the former Yugoslavia (ICTY) in The Hague closed, 25 years after it was set up by the United Nation\u27s Security Council (UN sc) Resolution 827. That decision by the UN SC, primarily in response to the brutality of the war in Bosnia and Herzegovina (BiH), completely changed the landscape of international law. American legal scholar Diane Orentlicher, a seasoned observer of the ICTY, provides in this book the most detailed assessment of its record to date. Countless journal articles, books, documentaries and panels, in the former Yugoslavia, The Hague and elsewhere discussed the ICTY but only in recent years has \u27impact\u27 become the focus of attention. Arguably, that was a consequence of the growing realisation that the tribunal cannot possibly do all that its numerous supporters hoped for. Now, Orentlicher has published a book that explores that, in what is obviously a result of long-term immersion in the topic, and countless interviews over the years

On sums of two Fibonacci numbers that are powers of numbers with limited Hamming weight

In 2018, Luca and Patel conjectured that the largest perfect power representable as the sum of two Fibonacci numbers is $3864^2 = F_{36} + F_{12}$. In other words, they conjectured that the equation \begin{equation}\tag{$\ast$}\label{eq:abstract} y^a = F_n + F_m \end{equation} has no solutions with $a\geq 2$ and $y^a > 3864^2$. While this is still an open problem, there exist several partial results. For example, recently Kebli, Kihel, Larone and Luca proved an explicit upper bound for $y^a$, which depends on the size of $y$. In this paper, we find an explicit upper bound for $y^a$, which only depends on the Hamming weight of $y$ with respect to the Zeckendorf representation. More specifically, we prove the following: If $y = F_{n_1}+ \dots + F_{n_k}$ and equation \eqref{eq:abstract} is satisfied by $y$ and some non-negative integers $n,m$ and $a\geq 2$, then $$y^a \leq \exp\left(C{(\varepsilon)} \cdot k^{(3+\varepsilon)k^2} \right).$$ Here, $\varepsilon >0$ can be chosen arbitrarily and $C(\varepsilon)$ is an effectively computable constant.Comment: 14 page

Double scattering of light from biophotonic nanostructures with short-range order

We investigate the physical mechanism for color production by isotropic nanostructures with short-range order in bird feather barbs. While the primary peak in optical scattering spectra results from constructive interference of singly-scattered light, many species exhibit secondary peaks with distinct characteristic. Our experimental and numerical studies show that these secondary peaks result from double scattering of light by the correlated structures. Without an analog in periodic or random structures, such a phenomenon is unique for short-range ordered structures, and has been widely used by nature for non-iridescent structural coloration.Comment: 10 pages, 4 figure

Subtle design changes control the difference in colour reflection from the dorsal and ventral wing-membrane surfaces of the damselfly Matronoides cyaneipennis.

The hind wings of males of the damselfly Matronoides cyaneipennis exhibit iridescence that is blue dorsally and green ventrally. These structures are used semiotically in agonistic and courtship display. Transmission electron microscopy reveals these colours are due to two near-identical 5-layer distributed Bragg reflectors, one placed either side of the wing membrane. Interestingly the thicknesses of corresponding layers in each distributed Bragg reflector are very similar for all but the second layer from each outer surface. This one key difference creates the significant disparity between the reflected spectra from the distributed Bragg reflectors and the observed colours of either side of the wing. Modelling indicates that modifications to the thickness of this layer alone create a greater change in the peak reflected wavelength than is observed for similar modifications to the thickness of any other layer. This results in an optimised and highly effective pair of semiotic reflector systems, based on extremely comparable design parameters, with relatively low material and biomechanical costs.Pete Vukusic acknowledges the financial support of AFOSR grant FA9550-10-1-0020. We thank D.G. Stavenga for critical reading of the manuscript

Classification of peacock feather reflectance using principal component analysis similarity factors from multispectral imaging data

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Iridescent structural colors in biology exhibit sophisticated spatially-varying reflectance properties that depend on both the illumination and viewing angles. The classification of such spectral and spatial information in iridescent structurally colored surfaces is important to elucidate the functional role of irregularity and to improve understanding of color pattern formation at different length scales. In this study, we propose a non-invasive method for the spectral classification of spatial reflectance patterns at the micron scale based on the multispectral imaging technique and the principal component analysis similarity factor (PCASF). We demonstrate the effectiveness of this approach and its component methods by detailing its use in the study of the angle-dependent reflectance properties of Pavo cristatus (the common peacock) feathers, a species of peafowl very well known to exhibit bright and saturated iridescent colors. We show that multispectral reflectance imaging and PCASF approaches can be used as effective tools for spectral recognition of iridescent patterns in the visible spectrum and provide meaningful information for spectral classification of the irregularity of the microstructure in iridescent plumage.This research was developed during a visiting research stay of Dr. José M. Medina in the Departamento de Óptica, Universidad de Granada, Spain. We thank to José Medina and Rosalía Ruiz who provided the peacock samples, to David Porcel and Juan de Dios Bueno from the Servicio de Microscopía, (Centro de Instrumentación Científica, Universidad de Granada) for technical assessment, and to the Color Imaging Group (Universidad de Granada) for their hardware partial support. JMM and JAD acknowledge the Departmento de Óptica, Universidad de Granada, Spain. PV acknowledges USAF funding (FA9550-10-1-0020)