Sedimentary deposits and bioturbation in an Early Cretaceous subarctic stormy greenhouse shelf environment

This study of the Aptian lower part of the Carolinefjellet Formation in Svalbard, Norwegian high Arctic, is based on well cores and outcrop section in the Adventdalen area of Spitsbergen and reports on the deposits and bioturbation structures of an ancient subpolar marine shelf from a well-known period of global greenhouse climate. The study documents the sedimentation conditions and benthic fauna activity on a warm-water aggrading shelf subject to harsh Arctic wave climate and eurybatic base-level changes, with episodic bottom incursions of cold polar water. Lithofacies associations and 38 observed ichnotaxa represent subenvironments ranging from offshore to lower shoreface and hosting the Cruziana ichnofacies in its distal to proximal expression, with a brief mid-Aptian encroachment of middle shoreface zone with a distal expression of the Skolithos ichnofacies. The ichnofacies are variously impoverished compared to their archetypes. The sediment bioturbation intensity varies, but similar lithofacies associations show a comparable intensity throughout the stratigraphic succession, which indicates an ichnofauna ecology controlled by the seafloor hydraulic regime and oxygenation, and thus mainly by the wave climate and relative sea-level changes. Sandstone tempestites indicate high-frequency storms, commonly exceeding the magnitude of largest modern hurricane events. The study confirms that a change in global climate mode, such as the Early Cretaceous warming, entails extreme weather conditions.publishedVersio

A micro-magneto-Raman scattering study of graphene on a bulk graphite substrate

We report on a magneto-Raman scattering study of graphene flakes located on the surface of a bulk graphite substrate. By spatially mapping the Raman scattering response of the surface of bulk graphite with an applied magnetic field, we pinpoint specific locations which show the electronic excitation spectrum of graphene. We present the characteristic Raman scattering signatures of these specific locations. We show that such flakes can be superimposed with another flake and still exhibit a graphene-like excitation spectrum. Two different excitation laser energies (514.5 and 720 nm) are used to investigate the excitation wavelength dependence of the electronic Raman scattering signal.Comment: 6 pages, 5 figure

Multiple magneto-phonon resonances in graphene

Our low-temperature magneto-Raman scattering measurements performed on graphene-like locations on the surface of bulk graphite reveal a new series of magneto-phonon resonances involving both K-point and Gamma-point phonons. In particular, we observe for the first time the resonant splitting of three crossing excitation branches. We give a detailed theoretical analysis of these new resonances. Our results highlight the role of combined excitations and the importance of multi-phonon processes (from both K and Gamma points) for the relaxation of hot carriers in graphene.Comment: 20 pages, 11 figure

Novel approach for efficient predictions properties of large pool of nanomaterials based on limited set of species: nano-read-across

Creating suitable chemical categories and developing read-across methods, supported by quantum mechanical calculations, can be an effective solution to solving key problems related to current scarcity of data on the toxicity of various nanoparticles. This study has demonstrated that by applying a nano-read-across, the cytotoxicity of nano-sized metal oxides could be estimated with a similar level of accuracy as provided by quantitative structure-activity relationship for nanomaterials (nano-QSAR model(s)). The method presented is a suitable computational tool for the preliminary hazard assessment of nanomaterials. It also could be used for the identification of nanomaterials that may pose potential negative impact to human health and the environment. Such approaches are especially necessary when there is paucity of relevant and reliable data points to develop and validate nano-QSAR model

Using the fractional interaction law to model the impact dynamics in arbitrary form of multiparticle collisions

Using the molecular dynamics method, we examine a discrete deterministic model for the motion of spherical particles in three-dimensional space. The model takes into account multiparticle collisions in arbitrary forms. Using fractional calculus we proposed an expression for the repulsive force, which is the so called fractional interaction law. We then illustrate and discuss how to control (correlate) the energy dissipation and the collisional time for an individual article within multiparticle collisions. In the multiparticle collisions we included the friction mechanism needed for the transition from coupled torsion-sliding friction through rolling friction to static friction. Analysing simple simulations we found that in the strong repulsive state binary collisions dominate. However, within multiparticle collisions weak repulsion is observed to be much stronger. The presented numerical results can be used to realistically model the impact dynamics of an individual particle in a group of colliding particles.Comment: 17 pages, 8 figures, 1 table; In review process of Physical Review

Surface and electronic structure of MOCVD-grown Ga(0.92)In(0.08)N investigated by UV and X-ray photoelectron spectroscopies

The surface and electronic structure of MOCVD-grown layers of Ga(0.92)In(0.08)N have been investigated by means of photoemission. An additional feature at the valence band edge, which can be ascribed to the presence of In in the layer, has been revealed. A clean (0001)-(1x1) surface was prepared by argon ion sputtering and annealing. Stability of chemical composition of the investigated surface subjected to similar ion etching was proven by means of X-ray photoemission spectroscopy.Comment: 13 pages, 6 figure

Efficient optical activation of ion-implanted Zn acceptors in GaN by annealing under 10 kbar N2 overpressure

We continue our investigations into the optical activation of Zn-implanted GaN annealed under ever higher N2 overpressure. The samples studied were epitaxial GaN/sapphire layers of good optical quality which were implanted with a 1013 cm−2 dose of Zn+ ions at 200 keV, diced into equivalent pieces and annealed under 10 kbar of N2. The N2 overpressure permitted annealing at temperatures up to 1250°C for 1 hr without GaN decomposition. The blue Zn-related photoluminescence (PL) signal rises sharply with increasing anneal temperature. The Zn-related PL intensity in the implanted sample annealed at 1250°C exceeded that of the epitaxially doped GaN:Zn standard proving that high temperature annealing of GaN under kbar N2 overpressure can effectively remove implantation damage and efficiently activate implanted dopants in GaN. We propose a lateral LED device which could be fabricated using ion implanted dopants activated by high temperature annealing at high pressur

An ab initio and matrix isolation infrared study of the 1:1 C<SUB>2</SUB>H<SUB>2</SUB>-CHCl<SUB>3</SUB> adduct

The details of weak C-H&#183;&#183;&#183;&#960; interactions that control several inter and intramolecular structures have been studied experimentally and theoretically for the 1:1 C2H2-CHCl3 adduct. The adduct was generated by depositing acetylene and chloroform in an argon matrix and a 1:1 complex of these species was identified using infrared spectroscopy. Formation of the adduct was evidenced by shifts in the vibrational frequencies compared to C2H2 and CHCl3 species. The molecular structure, vibrational frequencies and stabilization energies of the complex were predicted at the MP2/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels. Both the computational and experimental data indicate that the C2H2-CHCl3 complex has a weak hydrogen bond involving a C-H&#183;&#183;&#183;&#960; interaction, where the C2H2 acts as a proton acceptor and the CHCl3 as the proton donor. In addition, there also appears to be a secondary interaction between one of the chlorine atoms of CHCl3 and a hydrogen in C2H2. The combination of the C-H&#183;&#183;&#183;&#960; interaction and the secondary Cl&#183;&#183;&#183;H interaction determines the structure and the energetics of the C2H2-CHCl3 complex. In addition to the vibrational assignments for the C2H2-CHCl3 complex we have also observed and assigned features owing to the proton accepting C2H2 submolecule in the acetylene dimer

A quantum chemical cluster approach to study adsorption of some nitro compounds on the {100} α-quartz surface

This quantum chemical research, carried out using the density functional theory M06-2x DFT method with the 6‑31G(d,p) basis set and the three-layer ONIOM method (Gaussian09 program package), shows that alpha-quartz can moderately adsorb some nitrogen compounds, specifically, 2,4,6-trinitrotoluene (TNT),2,4-dinitrotoluene (DNT), 2,4-dinitroanisole (DNAn), and 3-nitro-1,2,4-triazole-5-one (NTO). The adsorption mechanism for all four considered nitro compounds was found to be similar. The main kind of surface binding is physical adsorption which occurs mainly due to hydrogen bonding, stacking interactions provided additional stabilization. From the Atoms-In-Molecules analysis of the studied systems it can be concluded that the adsorption energy is proportional to the number of intermolecular interactions between the target molecule and the surface. The energetically most favored position of the adsorbates over the mineral surface was found to be the parallel one.Квантовохимическое исследование с использованием теории функционала плотности методом M06-2x/6‑31G(d,p) и методом ONIOM-3 (программа Gaussian09) показало, что α-кварц способен адсорбировать 2,4,6-тринитротолуол, 2,4-динитротолуол, 2,4‑динитро-анизол и 3-нитро-1,2,4-триазол-5. Механизм адсорбции всех четырёх исследованных нитросоединений подобный – главная роль в связывании адсорбата с поверхностью принадлежит водородным связям, а стекинг-взаимодействия способствуют дополнительной стабилизации адсорбционных комплексов. Анализ изученных систем с помощью подхода «Атомы в молекулах» показал, что рассчитанная энергия адсорбции пропорциональна количеству связей между молекулами адсорбата и поверхностью. Установлено, что параллельное расположение молекулы нитросоединения по отношению к поверхности кварца является энергетически наиболее выгодным