Unusual Permutation Groups in Negative Curvature Carbon and Boron Nitride Structures

The concept of symmetry point groups for regular polyhedra can be generalized to special permutation groups to describe negative curvature polygonal networks that can be expanded to possible carbon and boron nitride structures through leapfrog transformations, which triple the number of vertices. Thus a D surface with 24 hep-tagons and 56 hexagons in the unit cell can be generated by a leapfrog transformation from the Klein figure consisting only of the 24 heptagons. The permutational symmetry of the Klein figure can be described by the simple PSL(2,7) (or heptakisoctahedral) group of order 168 with the conjugacy class structure E + 24C7 + 24C73 + 56C3 + 21C2 + 42C4. Analogous methods can be used to generate a D surface with 12 octagons and 32 hexagons by a leapfrog transformation from the Dyck figure consisting only of the 12 octagons. The permutational symmetry of the Dyck figure can be described by a group of order 96 and the conjugacy class structure E + 24S8 + 6C4 + 3C42 + 32C3 + 12C2 + 18S4. This group is not a simple group since it has a normal subgroup chain leading to the trivial group C1 through subgroups of order 48 and 16 not related to the octahedral or tetrahedral groups

Unusual Permutation Groups in Negative Curvature Carbon and Boron Nitride Structures

The concept of symmetry point groups for regular polyhedra can be generalized to special permutation groups to describe negative curvature polygonal networks that can be expanded to possible carbon and boron nitride structures through leapfrog transformations, which triple the number of vertices. Thus a D surface with 24 hep-tagons and 56 hexagons in the unit cell can be generated by a leapfrog transformation from the Klein figure consisting only of the 24 heptagons. The permutational symmetry of the Klein figure can be described by the simple PSL(2,7) (or heptakisoctahedral) group of order 168 with the conjugacy class structure E + 24C7 + 24C73 + 56C3 + 21C2 + 42C4. Analogous methods can be used to generate a D surface with 12 octagons and 32 hexagons by a leapfrog transformation from the Dyck figure consisting only of the 12 octagons. The permutational symmetry of the Dyck figure can be described by a group of order 96 and the conjugacy class structure E + 24S8 + 6C4 + 3C42 + 32C3 + 12C2 + 18S4. This group is not a simple group since it has a normal subgroup chain leading to the trivial group C1 through subgroups of order 48 and 16 not related to the octahedral or tetrahedral groups

Unconventional van der Waals heterostructures beyond stacking

Two-dimensional crystals provide exceptional opportunities for integrating dissimilar materials and forming interfaces where distinct properties and phenomena emerge. To date, research has focused on two basic heterostructure types: vertical van der Waals stacks and laterally joined monolayer crystals with in-plane line interfaces. Much more diverse architectures and interface configurations can be realized in the few-layer and multilayer regime, and if mechanical stacking and single-layer growth are replaced by processes taking advantage of self-organization, conversions between polymorphs, phase separation, strain effects, and shaping into the third dimension. Here, we highlight such opportunities for engineering heterostructures, focusing on group IV chalcogenides, a class of layered semiconductors that lend themselves exceptionally well for exploring novel van der Waals architectures, as well as advanced methods including in situ microscopy during growth and nanometer-scale probes of light-matter interactions. The chosen examples point to fruitful future directions and inspire innovative developments to create unconventional van der Waals heterostructures beyond stacking

Complejos supramoleculares dador-aceptor basados en éteres corona

Afin d'obtenir une meilleure compréhension de l'étape clé du système photosynthétique (la formation d’un état à charges séparées), une nouvelle famille de systèmes donneur-accepteur supramoléculaires a été préparée.Nous avons notamment acquis une meilleure compréhension de la nature des interactions π-π entre le C60 et les porphyrines (résultant d'un processus régi principalement par des forces de van der Waals) et de l'affinité des éthers couronnes vis-à-vis des fullerènes (résultant d'une combinaison entre interactions π-π, n-π et CH-π). Les propriétés supramoléculaires des dimères de porphyrines ont été aussi explorées, prouvant leur communication électronique à travers leurs sous-unités. Finalement, la coopérativité chélate d'un de nos systèmes a été évaluée par la molarité efficace.In order to gain a better understanding of the key step of the photosynthetic system (formation of a charged separated stated), a series of new supramolecular crown ether containing donnor-aceptor ensembles have been obtained.Notably we have gained further insight in the nature of π-π stacking between C60 and porphyrins (arising from a process mainly governed by van der Waals forces) and the affinity of crown ethers towards fullerenes(arising from an interplay of π-π, n-π and CH-π interactions). The properties of porphyrin arrays have been explored, evidencing the electronic communication through subunits. Finally, the chelate cooperativity of one our systems has also been assessed through the effective molarity

An integrated ecotoxicological assessment of the engineered nanoparticles, C60 fullerenes in different life stages of marine mussels, Mytilus edulis

Studies were undertaken to determine ecotoxicological effects of model manufactured or engineered nanoparticles (ENPs), either alone or in combination with a representative polycyclic aromatic hydrocarbon (i.e. PAHs: fluoranthene) at different levels of biological organisation (viz. biochemical, histological and behavioural levels) in a sentinel, widely distributed marine invertebrate species, Mytilus edulis. With the current and predicted levels of pollution in the marine and coastal environment, there is an urgent need to establish the potential effects of persistent and emerging contaminants which includes ENPs and PAHs, to protect human and environmental health. In this study, initially, it was aimed to optimise the induction of biotransformation enzyme P-450 as a robust biochemical tool and good progress (chapter 3) was made to standardise P-450 in mussel. Due to certain technical and logistic limitations however we could not apply measurement of P-450 as potential biochemical biomarkers in this species. The possibility of using glutathione levels instead in the cell-free component of haemolymph samples as an indicator of oxidative stress, in an analogous way to that used in mammals was evaluated (chapter 4). The evidence suggested that cell-free haemolymph samples collected from adductor muscle of Mytilus edulis may be significantly contaminated with intracellular contents of myocytes of this organ (i.e. adductor muscle) and adductor muscle tissue is more generally useful to determine glutathione system responses. The validation study of different assays using copper as a relevant environmental contaminant (chapter 5) suggested the existence of clear relationships between genotoxic (as determined by induction of DNA strand breaks using the Comet assay) and higher level effects. The results further suggested the feasibility of adoption of an integrated approach and robustness of selected biomarkers to evaluate short and long-term toxic effects of pollutants. A multiple biomarker approach was then used to determine the potential interactive effect of C60 fullerenes in combination with fluoranthene. Where appropriate analytical tools (i.e. ICP-MS, GC-MS) were used to determine the levels of contaminant exposure and characterise the properties of the ENPs. The combined exposure of fluoranthene and C60 fullerenes produced enhanced biological damage at approximately at an- “additive” rather than synergistic level, which appeared to be as a result of oxidative stress (chapter 6). The final experiments were carried out in both the early and adult life stages to test the potential toxicity resulting from photochemical transformation of C60 fullerenes in Mytilus edulis (chapter 7). In general, the results showed, for the first time, genotoxic and developmental impact of the photochemically transformed C60 fullerenes at different life stages of marine mussel. Further research is required to identify the degraded products of C60 fullerenes and to understand the mechanism by which fresh and aged C60 fullerenes induces biological responses including oxidative stress and affect ecologically relevant aquatic organisms at different life stages. The thesis has taken the opportunity to discuss (chapter 8) the importance of applications of biological responses in hazard and risk assessment posed by anthropogenic chemicals in a broader context

Evolution: From Big Bang to Nanorobots

The present volume is the fourth issue of the Yearbook series entitled ‘Evolution’. The title of the present volume is ‘From Big Bang to Nanorobots’. In this way we demonstrate that all phases of evolution and Big History are covered in the articles of the present Yearbook. Several articles also present the forecasts about future development. The main objective of our Yearbook as well as of the previous issues is the creation of a unified interdisciplinary field of research in which the scientists specializing in different disciplines could work within the framework of unified or similar paradigms, using the common terminology and searching for common rules, tendencies and regularities. At the same time for the formation of such an integrated field one should use all available opportunities: theories, laws and methods. In the present volume, a number of such approaches are used

Evolution: From Big Bang to Nanorobots

The present volume is the fourth issue of the Yearbook series entitled ‘Evolution’. The title of the present volume is ‘From Big Bang to Nanorobots’. In this way we demonstrate that all phases of evolution and Big History are covered in the articles of the present Yearbook. Several articles also present the forecasts about future development. The main objective of our Yearbook as well as of the previous issues is the creation of a unified interdisciplinary field of research in which the scientists specializing in different disciplines could work within the framework of unified or similar paradigms, using the common terminology and searching for common rules, tendencies and regularities. At the same time for the formation of such an integrated field one should use all available opportunities: theories, laws and methods. In the present volume, a number of such approaches are used

LDEF: 69 Months in Space. Second Post-Retrieval Symposium, part 2

This document is a compilation of papers presented at the Second Long Duration Exposure Facility (LDEF) Post-Retrieval Symposium. The papers represent the data analysis of the 57 experiments flown on the LDEF. The experiments include materials, coatings, thermal systems, power and propulsion, science (cosmic ray, interstellar gas, heavy ions, micrometeoroid, etc.), electronics, optics, and life science

Globalistics and globalization studies big history and global history

This yearbook is the fourth in the series with the title Globalistics and Globalization Studies. The subtitle of the present volume is Global History & Big History. The point is that today our global world really demands global knowledge. Thus, there are a few actively developing multidisciplinary approaches and integral disciplines among which one can name Global Studies, Global History and Big History. They all provide a connection between the past, present, and future. Big History with its vast and extremely heterogeneous field of research encompasses all the forms of existence and all timescales and brings together constantly updated information from the scientific disciplines and the humanities. Global History is transnational or world history which examines history from a global perspective, making a wide use of comparative history and of the history of multiple cultures and nations. Global Studies express the view of systemic and epistemological unity of global processes. Thus, one may argue that Global Studies and Globalistics can well be combined with Global History and Big History and such a multidisciplinary approach can open wide horizons for the modern university education as it helps to form a global view of various processes