Epsilon-Near-Zero Metamaterials

2021 ◽  
Author(s):  
Yue Li ◽  
Ziheng Zhou ◽  
Yijing He ◽  
Hao Li

This Element introduces the exotic wave phenomena arising from the extremely small optical refractive index, and sheds light on the underlying mechanisms, with a primary focus on the basic concepts and fundamental wave physics. The authors reveal the exciting applications of ENZ metamaterials, which have profound impacts over a wide range of fields of science and technology. The sections are organized as follows: in Section 2, the authors demonstrate the extraordinary wave properties in ENZ metamaterials, analyzing the unique wave dynamics and the resulting effects. Section 3 is dedicated to introducing various realization methods of the ENZ metamaterials with periodic and non-periodic styles. The applications of ENZ metamaterials are discussed in Sections 4 and 5, from the perspectives of microwave engineering, optics, and quantum physics. The authors close in Section 6 by presenting an outlook on the development of ENZ metamaterials and discussing the key challenges addressed in future works.

2009 ◽  
Vol 11 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Manasi Kumar ◽  
Erica Burman

We welcome readers to the first special issue (11.1) of the Journal of Health Management. We hope the readers find the articles and various reviews enriching and provocative, both in terms of the range of ideas and critical approaches addressed. The key theme of this double issue concerns the political limits of mega-development projects such as the Millennium Development Goals (MDGs). The primary focus of the articles collected here is to provide an insightful, constructive and in-depth critique of the United Nations (UN) MDGs along with critical deliberations on their short- and long-term implications not only for health management but also for a wide range of issues around development and social change.


2009 ◽  
Vol 5 (5) ◽  
pp. 625-627 ◽  
Author(s):  
Paul Schmid-Hempel

To Darwin, parasites were fascinating examples of adaptation but their significance as selective factors for a wide range of phenomena has only been studied in depth over the last few decades. This work has had its roots in behavioural/evolutionary ecology on the one hand, and in population biology/ecology on the other, thus shaping a new comprehensive field of ‘evolutionary parasitology’. Taking parasites into account has been a success story and has shed new light on several old questions such as sexual selection, the evolution of sex and recombination, changes in behaviour, adaptive life histories, and so forth. In the process, the topic of ecological immunology has emerged, which analyses immune defences in a framework of costs and benefits. Throughout, a recurrent theme is how to appropriately integrate the underlying mechanisms as evolved boundary conditions into a framework of studying the adaptive value of traits. On the conceptual side, major questions remain and await further study.


2021 ◽  
Author(s):  
Hervé Lethier

The World Heritage thematic study for Central Asia has been produced as a contribution to supporting the implementation of the World Heritage Convention in Central Asia. It provides a response to a Decision of the World Heritage Committee in order to identify outstanding areas with potential for future nomination to the World Heritage List with primary focus on criteria (ix) and (x) at the regional scale. The approach applied in this study, focusing on criteria (ix) and (x), follows that from the 2013 study on terrestrial biodiversity and the World Heritage List. Criteria (ix) and (x) are clearly the primary ones for recognition of extant biodiversity values, and they have been applied to a wide range of biodiversity features, including ecosystems, species, and ecological and/or biological processes. Although this study is an initial assessment, most areas and sites recommended here have appeared repeatedly as being of particular interest for biodiversity conservation during the work process, whether through literature analysis or in discussions with experts and specialists. The recommendations reflect the current level of knowledge that should be strengthened in the future, to ensure that the identified areas and sites are well supported with the necessary data and empirical evidence to address the requirements of the Operational Guidelines.


Bringing together a wide diversity of authors based on three continents and from different disciplinary backgrounds, this book offers analyses of a wide range of factors that characterize and that are shaping the future of the African Sahel. In forty chapters, organized in nine sections, the book examines this complex and rapidly changing region on multiple dimensions. Collectively, the book attempts to offer an understanding of the specificity of the Sahel, and to examine its core characteristics as shaped by the geographic, cultural, and political parameters that define it. Following a series of chapters focused on the shaping of the Sahelian space as a region, six chapters explore the distinct national trajectories of the countries of the political Sahel: Senegal, Mali, Niger, Burkina Faso, Mauritania, and Chad. The extraordinary combination of environmental, economic, and political challenges, and the ways in which Sahelian states and societies have responded, are the primary focus of the three subsequent sections, while the various parameters of the lived realities of these societies in motion are explored in the four final sections of the book. Transversally throughout, the chapters aim to offer an interdisciplinary and holistic view of the challenges and the dynamics that are shaping a region at a historical crossroads, and an understanding of the many factors that feed and perpetuate its vulnerabilities and fragilities, as well as its sources of resilience.


Author(s):  
Bernadette Baker ◽  
Clare O'Farrell

William James (1841–1910), working primarily out of the United States, and Michel Foucault (1926–1984), working primarily out of France, are two very different figures who both made an impact on current theories of education. Even if the primary focus of their work is not education, their ideas challenge what it is that makes education recognizable as education and takes issue with its very identity as a discipline. William James, who began publishing in the 1870s, is generally described as a philosopher and psychologist. He remains well-known for his work on pragmatism in the wake of Charles Sanders Peirce’s pragmaticism and for his work on religion, ethics, and mind theory, but he also devoted considerable time to the study of parapsychology and gave some attention to teacher education. Foucault has been variously described as a philosopher, historian, historian of ideas, and a social and political theorist. His work addressed an impressive array of fields across the sciences, literature, art, ethics, and institutional, political, and social history, and spanned a wide range of historical periods mainly in European and French history from the 13th century to the 20th century with later excursions into the Ancient Greek and early Christian eras. Foucault’s work has been widely, but selectively, deployed within education studies across the globe, with a strong focus on his notions of power, governmentality, surveillance, subjectivity, discourse, and ethics in their various iterations. James’s work has been relatively less deployed, with emphasis on the application of his version of pragmatism, theories of mind, and talks to teachers. The work of the two thinkers may be considered to overlap in two important ways: first, in their respective approaches to the notion of practice, namely the idea of philosophy as strategic and located in day-to-day concrete experience rather than occupying the rarefied realms of abstraction; and second, their interest in the margins of knowledge – knowledge that has been excluded by mainstream science and accepted ways of thinking. In the case of James, this interest manifests in his long-term studies in the field of parapsychology and in the case of Foucault in his interest in the meandering byways and monstrosities of the history of ideas, of long-forgotten knowledge rejected by the scientific mainstream or formulated on the margins of society.


2020 ◽  

The authors of the joint monograph "The Russo-Turkish War of 1877–1878: Hopes – Vicissitudes – Lessons", historians, culturologists and literary scholars, based on historical documents, archival materials, facts of public life and fiction writing, as well as "field work", give an updated vision of the sesquicentennial events, which played a significant role in the transformation of the geopolitical map of Europe and interethnic relations, and whose echoes are still heard today, often re-acquiring the acute relevance. The primary focus is on the Balkan policy of Russia and other major European countries; the Russian-Bulgarian military cooperation; the Russian-Bulgarian social and cultural ties; the refraction of historical realities in artistic creation, journalism and diaries. The book will be of interest to a wide range of researchers, university students and readers interested in the development of international relations, the history and culture of the Balkans, the Russian-Bulgarian dialogue.


Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2590 ◽  
Author(s):  
Huafeng Liu ◽  
Kai Luo ◽  
Shihao Tang ◽  
Danhua Peng ◽  
Fangjing Hu ◽  
...  

Metamaterial-based absorbers have been extensively investigated in the terahertz (THz) range with ever increasing performances. In this paper, we propose an all-dielectric THz absorber based on doped silicon. The unit cell consists of a silicon cross resonator with an internal cross-shaped air cavity. Numerical results suggest that the proposed absorber can operate from THz to far-infrared regimes, having an average power absorption of ∼95% between 0.6 and 10 THz. Experimental results using THz time-domain spectroscopy show a good agreement with simulations. The underlying mechanisms for broadband absorption are attributed to the combined effects of multiple cavities modes formed by silicon resonators and bulk absorption in the doped silicon substrate, as confirmed by simulated field patterns and calculated diffraction efficiency. This ultra-wideband absorption is polarization insensitive and can operate across a wide range of the incident angle. The proposed absorber can be readily integrated into silicon-based photonic platforms and used for sensing, imaging, energy harvesting and wireless communications applications in the THz/IR range.


Marine Drugs ◽  
2020 ◽  
Vol 18 (12) ◽  
pp. 634
Author(s):  
Han Xiao ◽  
Jiarui Zhao ◽  
Chang Fang ◽  
Qi Cao ◽  
Maochen Xing ◽  
...  

Fucoxanthin is a natural carotenoid derived mostly from many species of marine brown algae. It is characterized by small molecular weight, is chemically active, can be easily oxidized, and has diverse biological activities, thus protecting cell components from ROS. Fucoxanthin inhibits the proliferation of a variety of cancer cells, promotes weight loss, acts as an antioxidant and anti-inflammatory agent, interacts with the intestinal flora to protect intestinal health, prevents organ fibrosis, and exerts a multitude of other beneficial effects. Thus, fucoxanthin has a wide range of applications and broad prospects. This review focuses primarily on the latest progress in research on its pharmacological activity and underlying mechanisms.


2019 ◽  
Vol 7 (6) ◽  
pp. 186 ◽  
Author(s):  
Umberto Andriolo

Within the nearshore area, three wave transformation domains can be distinguished based on the wave properties: shoaling, surf, and swash zones. The identification of these distinct areas is relevant for understanding nearshore wave propagation properties and physical processes, as these zones can be related, for instance, to different types of sediment transport. This work presents a technique to automatically retrieve the nearshore wave transformation domains from images taken by coastal video monitoring stations. The technique exploits the pixel intensity variation of image acquisitions, and relates the pixel properties to the distinct wave characteristics. This allows the automated description of spatial and temporal extent of shoaling, surf, and swash zones. The methodology was proven to be robust, and capable of spotting the three distinct zones within the nearshore, both cross-shore and along-shore dimensions. The method can support a wide range of coastal studies, such as nearshore hydrodynamics and sediment transport. It can also allow a faster and improved application of existing video-based techniques for wave breaking height and depth-inversion, among others.


Sign in / Sign up

Export Citation Format

Share Document