Stochastic growth equations on growing domains

The dynamics of linear stochastic growth equations on growing substrates is studied. The substrate is assumed to grow in time following the power law $t^\gamma$, where the growth index $\gamma$ is an arbitrary positive number. Two different regimes are clearly identified: for small $\gamma$ the interface becomes correlated, and the dynamics is dominated by diffusion; for large $\gamma$ the interface stays uncorrelated, and the dynamics is dominated by dilution. In this second regime, for short time intervals and spatial scales the critical exponents corresponding to the non-growing substrate situation are recovered. For long time differences or large spatial scales the situation is different. Large spatial scales show the uncorrelated character of the growing interface. Long time intervals are studied by means of the auto-correlation and persistence exponents. It becomes apparent that dilution is the mechanism by which correlations are propagated in this second case.Comment: Published versio

Planetary nebulae in the inner Milky Way

New abundances of planetary nebulae located towards the bulge of the Galaxy are derived based on observations made at LNA (Brazil). We present accurate abundances of the elements He, N, S, O, Ar, and Ne for 56 PNe located towards the galactic bulge. The data shows a good agreement with other results in the literature, in the sense that the distribution of the abundances is similar to those works. From the statistical analysis performed, we can suggest a bulge-disk interface at 2.2 kpc for the intermediate mass population, marking therefore the outer border of the bulge and inner border of the disk.Comment: 2 pages, 1 figure, uses iaus.cls, in press, IAU Symp. 265, Chemical abundances in the Universe: Connecting the first Stars to Planets, Ed. K. Cunha, M. Spite, B. Barbu

Exploring the Triplet Excited State Potential Energy Surfaces of a Cyclometalated Pt(II) Complex: Is There Non-Kasha Emissive Behavior?

In this Article, we address the complexity of the emissive processes of a square-planar heteroleptic Pt(II) complex bearing 2-phenylpyridine (ppy) as cyclometalated ligand and an acetylacetonate derivative (dbm) as ancillary ligand. The origins of emission were identified with the help of density functional theory (DFT) and quadratic response (QR) time-dependent (TD)-DFT calculations including spin–orbit coupling (SOC). To unveil the photodeactivation mechanisms, we explored the triplet potential energy surfaces and computed the SOCs and the radiative decay rates (kr) from possible emissive states. We find that emission likely originates from a higher-lying 3MLCT/3LLCT state and not from the Kasha-like 3MLCT/3LCdbm state. The temperature-dependent nonradiative deactivation mechanisms were also elucidated. The active role of metal-centered (3MC) triplet excited states is confirmed for these deactivation pathways

Abundances of Recently Discovered Planetary Nebulae Towards the Galactic Bulge

In this work we report spectrophotometric observations of a planetary nebula sample towards the galactic bulge. A total of 45 PNe was observed and their physical parameters (electron density and temperature) were derived. Ionic abundances were calculated using a three-level atom model and abundances were derived through ionisation correction factors. Results show low abundance objects at high galactic latitudes, indicating a possible vertical gradient inside the bulge. A few objects with low N/O ratio were found, which could originated from old, low mass progenitors

A Data Fusion Technique to Detect Wireless Network Virtual Jamming Attacks

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Wireless communications are potentially exposed to jamming due to the openness of the medium and, in particular, to virtual jamming, which allows more energy-efficient attacks. In this paper we tackle the problem of virtual jamming attacks on IEEE 802.11 networks and present a data fusion solution for the detection of a type of virtual jamming attack (namely, NAV attacks), based on the real-time monitoring of a set of metrics. The detection performance is evaluated in a number of real scenarios

Field Theory of Propagating Reaction-Diffusion Fronts

The problem of velocity selection of reaction-diffusion fronts has been widely investigated. While the mean field limit results are well known theoretically, there is a lack of analytic progress in those cases in which fluctuations are to be taken into account. Here, we construct an analytic theory connecting the first principles of the reaction-diffusion process to an effective equation of motion via field-theoretic arguments, and we arrive at the results already confirmed by numerical simulations

Blow-up of the hyperbolic Burgers equation

The memory effects on microscopic kinetic systems have been sometimes modelled by means of the introduction of second order time derivatives in the macroscopic hydrodynamic equations. One prototypical example is the hyperbolic modification of the Burgers equation, that has been introduced to clarify the interplay of hyperbolicity and nonlinear hydrodynamic evolution. Previous studies suggested the finite time blow-up of this equation, and here we present a rigorous proof of this fact

Electronic Structure of N₂P₂ Four-Membered Rings

The biradicaloid character of the ground-state structures of N2P2 rings is studied by using the high-level ab initio multiconfigurational CASPT2/CASSCF method. In order to obtain accurate descriptors, we combine two criteria: 1) singlet–triplet energy gaps and 2) relative values of the occupation numbers for bonding and antibonding orbitals associated with the radical sites. The singlet–triplet energy gaps, the occupation numbers of antibonding-like orbitals, and the weights of the main configuration state functions (CSFs) of the ground-state wavefunctions, that is, Ψ(1A1), are used to derive the biradicaloid character that ranges from 10–15 %

The populations of planetary nebulae in the direction of the Galactic bulge

We have observed 44 planetary nebulae (PNe) in the direction of the Galactic bulge, and merged our data with published ones. We have distinguished, in the merged sample of 164 PNe, those PNe most likely to prtain physically to the Galactic bulge and those most likely to belong to the Galactic disk. We have determined the chemical composition of all the 164 objects in a coherent way. We looked for stellar emission features and discovered 14 new [WR] stars and 15 new weak emission line central stars. The analyzed data led us to the following conclusions: (1) The spectral type distribution of [WR] stars is very different in the bulge and in the disk of the Galaxy. However, the observed distributions are strongly dependent on selection effects. (2) The proportion of [WR] PNe is significantly larger in the bulge than in the disk. (3) The oxygen abundances in [WR] stars do no appear to be significantly affected by nucleosynthesis and mixing in the progenitors. (4) The O/H gradient of the Galactic disk PNe population flattens in the most internal parts of the Galaxy. (5) The median oxygen abundance in the bulge PN population is larger by 0.2 dex than in the disk population seen in the direction of the bulge. (6) Bulge PNe with smaller O/H tend to have smaller radial velocities. (7) The oxygen abundance distribution of bulge PNe is similar in shape to that of the metallicity distribution of bulge giants, but significantly narrower. (8) The location of SB 32 (PN G 349.7-09.1) in the (V_lsr, l_II) diagram and its low oxygen abundance argues that it probably belongs to the halo population.Comment: 14 pages, 16 figures. Accepted for publication in A&