UV active plasmons in alkali and alkaline earth intercalated graphene

The interband pi and pi+sigma plasmons in pristine graphene and the Dirac plasmon in doped graphene are not applicable, since they are broad or weak, and weakly couple to an external longitudinal or electromagnetic probe. Therefore, the ab initio Density Function Theory is used to demonstrate that the chemical doping of the graphene by the alkali or alkaline earth atoms dramatically changes the poor graphene excitation spectrum in the ultra-violet frequency range (4 - 10 eV). Four prominent modes are detected. Two of them are the intra-layer plasmons with the square-root dispersion, characteristic for the two-dimensional modes. The remaining two are the inter-layer plasmons, very strong in the long-wavelength limit but damped for larger wave-vectors. The optical absorption calculations show that the inter-layer plasmons are both optically active, which makes these materials suitable for small organic molecule sensing. This is particularly intriguing because the optically active two-dimensional plasmons have not been detected in other materials

A Semantic Framework for Declarative and Procedural Knowledge

In any scientic domain, the full set of data and programs has reached an-ome status, i.e. it has grown massively. The original article on the Semantic Web describes the evolution of a Web of actionable information, i.e.\ud information derived from data through a semantic theory for interpreting the symbols. In a Semantic Web, methodologies are studied for describing, managing and analyzing both resources (domain knowledge) and applications (operational knowledge) - without any restriction on what and where they\ud are respectively suitable and available in the Web - as well as for realizing automatic and semantic-driven work\ud ows of Web applications elaborating Web resources.\ud This thesis attempts to provide a synthesis among Semantic Web technologies, Ontology Research, Knowledge and Work\ud ow Management. Such a synthesis is represented by Resourceome, a Web-based framework consisting of two components which strictly interact with each other: an ontology-based and domain-independent knowledge manager system (Resourceome KMS) - relying on a knowledge model where resource and operational knowledge are contextualized in any domain - and a semantic-driven work ow editor, manager and agent-based execution system (Resourceome WMS).\ud The Resourceome KMS and the Resourceome WMS are exploited in order to realize semantic-driven formulations of work\ud ows, where activities are semantically linked to any involved resource. In the whole, combining the use of domain ontologies and work ow techniques, Resourceome provides a exible domain and operational knowledge organization, a powerful engine for semantic-driven work\ud ow composition, and a distributed, automatic and\ud transparent environment for work ow execution

Analysis of DNA-Damage Response to ionizing radiation in serum-shock synchronized human fibroblasts.

Many aspects of cellular physiology, including cellular response to genotoxic stress, are related to the circadian rhythmicity induced by the molecular clock. The current study investigated if the cellular response to DNA damage is in relation to endogenous expression levels of the PER2 protein, a key component of the molecular regulatory system that confers rhythmicity in mammalian cells. Human normal fibroblasts (CCD-34Lu) were subjected to serum shock to induce circadian oscillations of the PER2 protein and then irradiated with \u3b3- rays at times corresponding to the trough and peak expression of the PER2 protein. To better examine cellular response to DNA damage, the experiments performed in this study were carried out in non-proliferating CCD-34Lu fibroblasts in order to maintain the cell and circadian cycles separated while they were being exposed to genotoxic stress. Study results demonstrated that clonogenic cell survival, double-strand break repair kinetics, and TP53 protein levels were affected in the cells irradiated at the trough than in those irradiated at peak expression of the PER2 protein

Singularities in core-level spectra near metallic surfaces

Calculations of the screening shift and dynamical singularity index of the structureless core hole placed near and inside the metallic slab are presented, where the screening mechanism is described using the quantum-mechanical response function calculated in the local density approximation. Core-hole screening shifts show oscillations which are compared with the experimental results. Spatial dependence of the static singularity index, besides experimentally observed enhancement at the surface, shows some new features (bulk oscillations) which were not yet experimentally observed. The dynamical singularity index is used to calculate complete core hole spectrum, including singular line shapes and bulk and surface plasmon losses, and the results explain very well some observed features in the experimental photoemission spectra

Surface spectral functions and excitation frequencies in thin metallic films

Surface spectral functions are calculated for very thin metal slabs, containing both collective modes and single-particle excitations. This is achieved by calculating the surface dielectric function ε_p(Q,ω) for the thin jellium slab in the density functional theory and random phase approximation, using Kohn-Sham wavefunctions within the local density approximation, from which we derive the surface spectral functions. Influence of the slab thickness on the excitation spectra is studied, and the dispersion relations of the collective modes are obtained. Slightly modified fast converging method for the calculation of the Kohn-Sham wavefunctions is presented

Propagators and spectra of surface polaritons in metallic slabs: Effects of quantum-mechanical nonlocality

A transparent and compact method for the calculation of the electromagnetic-field propagator in presence of a thin metallic slab is developed. Electron wave functions for the slab are obtained numerically by using density-functional theory within the local density approximation, and used to construct the slab conductivity tensor. Expressions for the free-photon Green’s function and photon self-energy (i.e., slab conductivity tensor) in terms of electronic wave functions are derived analytically, taking advantage of the symmetry of the problem and separating it in s and p polarizations. Dyson equation for the polariton propagator is analytically prepared to be solved in two steps: first, solving the Dyson equation with only paramagnetic (nonlocal) part of photon self-energy included, and second, renormalizing such propagator because of its interaction with diamagnetic (local) polarizations. Such approach allows us to take both polarization mechanisms into account as well as their mutual influence. Long-wavelength and quasistatic limits of our results are derived and compared with previous results. Finally, the method is used to calculate spectra of polaritons, i.e., electromagnetic excitations produced by an oscillating dipole placed in the vicinity or inside a metallic slab

Microscopic theory of the noncontact van der Waals interaction: Application to layered systems

In this paper we introduce an efficient method for the calculation of the noncontact van der Waals interaction between two metallic slabs of arbitrary thicknesses and densities. Because of the numerical resolution, the method enables the detailed examination of transition from the classical to the intermediate region of the vdW interaction. We also demonstrate how this new microscopic formulation reduces to the classical Lifshitz formula for the van der Waals interaction. This method is applied to calculate the interaction between various planar systems and compared with some previous results

Površinske spektralne funkcije i frekvencije pobuđenja u tankim metalnim slojevima

Surface spectral functions are calculated for very thin metal slabs, containing both collective modes and single-particle excitations. This is achieved by calculating the surface dielectric function εp(Q, ω) for the thin jellium slab in the density functional theory and random phase approximation, using Kohn-Sham wavefunctions within the local density approximation, from which we derive the surface spectral functions. Influence of the slab thickness on the excitation spectra is studied, and the dispersion relations of the collective modes are obtained. Slightly modified fast converging method for the calculation of the Kohn-Sham wavefunctions is presented.Izračunali smo površinske spektralne funkcije vrlo tankih metalnih slojeva koje sadrže kolektivne modove i jednočestična pobuđenja. To smo postigli računanjem površinske dielektrične funkcije εp(Q, ω) za tanak sloj elektronskog plina u teoriji funkcionala gustoće i aproksimaciji slučajnih faza, primjenom Kohn-Shamovih valnih funkcija u aproksimaciji lokalne gustoće, na osnovi koje se izvode površinske spektralne funkcije. Proučavali smo utjecaj debljine sloja na spektre pobuđenja i dobili disperzijske relacije za kolektivne modove. Izlažemo malo promijenjenu metodu za računanje Kohn-Shamovih valnih funkcija koja brzo konvergira

Površinske spektralne funkcije i frekvencije pobuđenja u tankim metalnim slojevima

Surface spectral functions are calculated for very thin metal slabs, containing both collective modes and single-particle excitations. This is achieved by calculating the surface dielectric function εp(Q, ω) for the thin jellium slab in the density functional theory and random phase approximation, using Kohn-Sham wavefunctions within the local density approximation, from which we derive the surface spectral functions. Influence of the slab thickness on the excitation spectra is studied, and the dispersion relations of the collective modes are obtained. Slightly modified fast converging method for the calculation of the Kohn-Sham wavefunctions is presented.Izračunali smo površinske spektralne funkcije vrlo tankih metalnih slojeva koje sadrže kolektivne modove i jednočestična pobuđenja. To smo postigli računanjem površinske dielektrične funkcije εp(Q, ω) za tanak sloj elektronskog plina u teoriji funkcionala gustoće i aproksimaciji slučajnih faza, primjenom Kohn-Shamovih valnih funkcija u aproksimaciji lokalne gustoće, na osnovi koje se izvode površinske spektralne funkcije. Proučavali smo utjecaj debljine sloja na spektre pobuđenja i dobili disperzijske relacije za kolektivne modove. Izlažemo malo promijenjenu metodu za računanje Kohn-Shamovih valnih funkcija koja brzo konvergira

TRENDS IN POPULATION SIZE OF OPHRYS ARGOLICA SUBSP. BISCUTELLA IN THE APPENNINO LUCANO-VAL D’AGRI-LAGONEGRESE NATIONAL PARK (ITALY)

n this study we focused on population monitoring of Ophrys argolica subsp. biscutella, an orchid endemic to the south of the Italian Peninsula belonging to the section Araniferae. The study concerned its main detected population located within the Appennino Lucano-Val d'Agri-Lagonegrese National Park (Basilicata Region, South Italy). Ten permanent plots of 10 × 10 m were annually surveyed from 2010 to 2015 using total counts of flowering plants. The following characters were measured: height of inflorescences, number of flowers, lost plants, fruiting plants and fruit set. Percentage cover of trees, shrubs, herbs and bare rocks were visually estimated in 1 × 1 m subplots and an accurate vegetation map of each plot was drawn. In regards to plant height and reproductive variables, no significant differences between the plots were detected. Similarly, with respect to population variables, no significant correlations with vegetation and environmental features (i.e. slope, aspect) emerged. On the contrary, a strong negative trend in the population size was observed (from 237 individuals in 2010 to 61 in 2015) and the number of plants per plot decreased from 23.7 individuals to 6.1 individuals. Reproductive variables (i.e. number of flowers, fruit set) showed a similar decreasing pattern. As for the lost of individuals we detected a higher incidence in 2011 (average number of lost plants per plot was 16.6) with 75% of lost spikes and fruit set amounting to zero. Although grazing management can heavily influence demographic parameters of Ophrys populations, there was no evidence of any kind of land cover or land use change. No appreciable differences were observed in vegetation cover, grazing type or grazing load. Moreover, no significant disturbance events occurred in this area. Finally, the inspection of meteorological data recorded during the monitoring interval lead to argue that the strong demographic decline of the Ophrys argolica subsp. biscutella population in the Appennino Lucano-Val d'Agri-Lagonegrese National Park must be mainly related to the late frost event that occurred in the spring of 2011