Ultrashort light bullets described by the two-dimensional sine-Gordon equation

By using a reductive perturbation technique applied to a two-level model, this study puts forward a generic two-dimensional sine-Gordon evolution equation governing the propagation of femtosecond spatiotemporal optical solitons in Kerr media beyond the slowly varying envelope approximation. Direct numerical simulations show that, in contrast to the long-wave approximation, no collapse occurs, and that robust (2+1)-dimensional ultrashort light bullets may form from adequately chosen few-cycle input spatiotemporal wave forms. In contrast to the case of quadratic nonlinearity, the light bullets oscillate in both space and time and are therefore not steady-state lumps

Stable topological modes in two-dimensional Ginzburg-Landau models with trapping potentials

Complex Ginzburg-Landau (CGL) models of laser media (with the cubic-quintic nonlinearity) do not contain an effective diffusion term, which makes all vortex solitons unstable in these models. Recently, it has been demonstrated that the addition of a two-dimensional periodic potential, which may be induced by a transverse grating in the laser cavity, to the CGL equation stabilizes compound (four-peak) vortices, but the most fundamental "crater-shaped" vortices (CSVs), alias vortex rings, which are, essentially, squeezed into a single cell of the potential, have not been found before in a stable form. In this work we report families of stable compact CSVs with vorticity S=1 in the CGL model with the external potential of two different types: an axisymmetric parabolic trap, and the periodic potential. In both cases, we identify stability region for the CSVs and for the fundamental solitons (S=0). Those CSVs which are unstable in the axisymmetric potential break up into robust dipoles. All the vortices with S=2 are unstable, splitting into tripoles. Stability regions for the dipoles and tripoles are identified too. The periodic potential cannot stabilize CSVs with S>=2 either; instead, families of stable compact square-shaped quadrupoles are found

Three-dimensional spatiotemporal optical solitons in nonlocal nonlinear media

We demonstrate the existence of stable three-dimensional spatiotemporal solitons (STSs) in media with a nonlocal cubic nonlinearity. Fundamental (nonspinning) STSs forming one-parameter families are stable if their propagation constant exceeds a certain critical value, that is inversely proportional to the range of nonlocality of nonlinear response. All spinning three-dimensional STSs are found to be unstable.Comment: 14 pages, 6 figures, accepted to PRE, Rapid Communication

Middle School Education in Music Media Literacy Could Combat the Potential Negative Effects of Exposure to Sexual Content in Music

The current study focused on examining the relationship between music media literacy and middle school students. The goal of the study was to bring awareness towards adding music media literacy in the middle school curriculum; in order to further educate middle school students on the potential negative effects of popular music on their attitudes and behaviors, help middle school students understand the processes involved in the creation of popular music, and help middle school students understand how popular music can reflect and impact society as a whole. Participants (n=20) were selected through social media ads, ads posted on listservs, and word of mouth. A series of analyses were conducted in SPSS to find any difference in how participants viewed music based on demographic factors. Results showed the students view the lyrics in music to be from real-life scenarios, such as sexualization, sexual activity, substance abuse, violence and aggression. As well, participants showed to view music as a portrayal of both men and women factually in the real-world. These findings support the need for music media literacy in middle school curriculum. Keywords : sexualization, high risk-behaviors, real-life scenario

AGROCHEMICAL STUDY IN THE AREA OF SILIȘTEA-GUMEȘTI TELEORMAN COUNTY, WITH AN AREA OF 210 HA, WITH THE PURPOSE OF ELABORATING THE FERTILIZATION PLAN ON CROPS

In order to carry out this study, work was carried out on the morphological, physical and chemical characterization, determining the productive potential of the soil cover, enunciating the measures of soil improvement and elaborating the fertilization plan on crops. The field stage includes the presentation of general and local ecopedological conditions. In this regard, observations were made on the territory from the point of view of each ecopedological factor. Based on the movement on the ground, observations were made on the micro-relief, the level of the groundwater, the vegetation and the degree of anthropization of the soil cover following the mobilization, preparation of the germination bed and current maintenance. The soil samples were collected according to the cadastral plan, with an area of 210 ha being located on the radius of SilișteaGumești commune, Teleorman county. For the characterization of the soil cover from the above mentioned surface, a soil profile and a few surveys were carried out, in order to correctly identify the representative soil type. Also, agrochemical mapping was performed, 44 soil samples were collected from the arable horizon (0-20 cm) in disturbed system (in plastic bags). The description of the pedogenetic conditions and the soil cover from soil boiling, was carried out according to the "Guide for the description in the field of the soil profile and the specific environmental conditions", authors: Munteanu I., Florea N., 2009 and "Methodology for the Development of Pedological Studies ", ICPA, 1987. The classification of soils at type and subtype level was made according to" Romanian Soil Taxonomy System (SRTS) ", ICPA, 2012

PEDOLOGICAL STUDY OF LAND SUITABILITY IN THE AREA OF MAVRODIN TELEORMAN COUNTY, REGARDING THE ARRANGEMENT OF IRRIGATION WITH WATER FROM ZOOTECHNICAL COMPLEXES

The studied area is located in the center of Teleorman County, belonging to the Mavrodin cadastral territory, currently used as an arable land. The pedological mapping was performed with the purpose of identifying the soil area, assessing its fertility as well as the suitability for irrigation with wastewater. In this regard, a soil profile was opened and several surveys were collected from soil samples in natural and modified settlements, for morphological, physical and chemical analyzes. The soil type identified is red preluvosol. Geomorphologically, the land is part of the Roman Plain, the subunit of Burnaz, between the Danube Lunca, the Vedea, Teleorman and Calniştei valleys, extended west to the Teleorman river and the eastern limit of the county. The ground level is maintained between 8-10 m, with small fluctuations depending on the terrain. The type of soil identified, is classified in the luvisoluri class, having the following sequence of horizons: Ao-AB-Bt-C. The criteria for classification into classes, subclasses and other subunits of land according to the suitability to irrigate with waste water are those mentioned in chap. 10 from MESP, vol II (ICPA, 1987) with some additions. According to Annex 11.1 of the MESP, vol II (ICPA, 1987), the following additional criteria intervene in the selection of lands that can be irrigated with wastewater (soil type, soil texture, soil volume, soil thickness, erosion, soil unevenness, groundwater depth, excess surface moisture, other restrictions

Light bullets in quadratic media with normal dispersion at the second harmonic

Stable two- and three-dimensional spatiotemporal solitons (STSs) in second-harmonic-generating media are found in the case of normal dispersion at the second harmonic (SH). This result, surprising from the theoretical viewpoint, opens a way for experimental realization of STSs. An analytical estimate for the existence of STSs is derived, and full results, including a complete stability diagram, are obtained in a numerical form. STSs withstand not only the normal SH dispersion, but also finite walk-off between the harmonics, and readily self-trap from a Gaussian pulse launched at the fundamental frequency.Comment: 4 pages, 5 figures, accepted to Phys. Rev. Let

Stable three-dimensional spinning optical solitons supported by competing quadratic and cubic nonlinearities

We show that the quadratic interaction of fundamental and second harmonics in a bulk dispersive medium, combined with self-defocusing cubic nonlinearity, give rise to completely localized spatiotemporal solitons (vortex tori) with vorticity s=1. There is no threshold necessary for the existence of these solitons. They are found to be stable against small perturbations if their energy exceeds a certain critical value, so that the stability domain occupies about 10% of the existence region of the solitons. We also demonstrate that the s=1 solitons are stable against very strong perturbations initially added to them. However, on the contrary to spatial vortex solitons in the same model, the spatiotemporal solitons with s=2 are never stable.Comment: latex text, 10 ps and 2 jpg figures; Physical Review E, in pres

Multidimensional solitons in periodic potentials

The existence of stable solitons in two- and three-dimensional (2D and 3D) media governed by the self-focusing cubic nonlinear Schr\"{o}dinger equation with a periodic potential is demonstrated by means of the variational approximation (VA) and in direct simulations. The potential stabilizes the solitons against collapse. Direct physical realizations are a Bose-Einstein condensate (BEC) trapped in an optical lattice, and a light beam in a bulk Kerr medium of a photonic-crystal type. In the 2D case, the creation of the soliton in a weak lattice potential is possible if the norm of the field (number of atoms in BEC, or optical power in the Kerr medium) exceeds a threshold value (which is smaller than the critical norm leading to collapse). Both "single-cell" and "multi-cell" solitons are found, which occupy, respectively, one or several cells of the periodic potential, depending on the soliton's norm. Solitons of the former type and their stability are well predicted by VA. Stable 2D vortex solitons are found too.Comment: 13 pages, 3 figures, Europhys. Lett., in pres