Families of stable and metastable solitons in coupled system of scalar fields

In this paper, we obtain stable and metastable soliton solutions of a coupled system of two real scalar fields with five five discrete points of vacua. These solutions have definite topological charges and rest energies and show classical dynamical stability. From a quantum point of view, however, the V-type solutions are expected to be unstable and decay to D-type solutions. The induced decay of a V-type soliton into two D-type ones is calculated numerically, and shown to be chiral, in the sense that the decay products do not respect left-right symmetry.Comment: 9 pages and 5 figure

String inspired explanation for the super-acceleration of our universe

We investigate the effect of the bulk content in the general Gauss-Bonnet braneworld on the evolution of the universe. We find that the Gauss-Bonnet term and the combination of the dark radiation and the matter content of the bulk play a crucial role in the universe evolution. We show that our model can describe the super-acceleration of our universe with the equation of state of the effective dark energy in agreement with observations.Comment: 12 pages, 9 figures, references adde

Boundary Conditions in Stepwise Sine-Gordon Equation and Multi-Soliton Solutions

We study the stepwise sine-Gordon equation, in which the system parameter is different for positive and negative values of the scalar field. By applying appropriate boundary conditions, we derive relations between the soliton velocities before and after collisions. We investigate the possibility of formation of heavy soliton pairs from light ones and vise versa. The concept of soliton gun is introduced for the first time; a light pair is produced moving with high velocity, after the annihilation of a bound, heavy pair. We also apply boundary conditions to static, periodic and quasi-periodic solutions.Comment: 14 pages, 8 figure

Effect of different salinity on ions, osmolarity, water concentration of body tissue, gill chloride cells and mortality percentage of juveniles of Caspian roach (Rutilus frisii kutum Kamensky 1901)

Changes of ions (Na+, Ca, K+), osmolarity and water concentration of body tissue, size and number of gill chloride cells as well as mortality percentage of the juveniles Caspian roaches in weight groups of 0.2, 0.5 & 1g water satiny stress were studied. The salinities tested were 0 (fresh water), 7, 12.5 & 16 g/lit and the assessments were completed 0, 12, 24, 48 & 72 hours after exposure. Results showed that ions and osmolarity of juveniles weighting 0.2 & 0.5g in salinities of 0 up to 12.5g/lit increased significantly during the first 12 hours (P'<0.05). These values then showed down were trend to the values recorded for fresh water. Water concentration of body tissue reached the minimum mean value in 12 hours (P<0.05) in salinity of 12.5 g/lit and then showed upward trend to the value obtained for freshwater. Ions and osmolarity of body tissue of the juveniles increased and water concentration of body tissue decreased significant after the first 12 hours of transferring into salinity of 16g/lit (P<0.05). Weight changes in juveniles of 1g in salinities of 0 up to 16g/lit was similar to juveniles of 0.2 & 0.5g in salinities of 0 up to 12.5gllit and the maximum mean values of ions and osmolarity and the minimum value of water concentration body tissue in 16g/lit salinity in hour 12 (P<0.05). Size and number of gill chloride cells of juveniles weighting 0.2 & 0.5g in salinities of 0 up to 12.5g/lit increased significantly during the first 12 hours of exposure (P<0.05) and reached the maximum mean values in 12.5g/lit salinity 12 & 24 hours after exposure, respectively (P<0.05) and showed invisible changes up to the end of the test. Size and number of chloride cells of the juveniles increased after the first 12 hours of transferring into salinity of 16g/lit (P<0.05). Changes of the indices in juveniles weighting 1gin salinities of 0 up to 16g/lit was similar to juveniles of 0.2 & 0.5g kept in salinities of 0 up to 12.5gtlit and the maximum values was in 12 and 24 hours after exposure, respectively (P<0.05). Ions and osmolarity of body tissue and size and number of chloride cells increased significantly with increase of salinity and weight and water salinity and water concentration of body tissue decreased significantly with increase in water salinity and increased in fish weight (P<0.05). Juveniles weighting 0.2 up to 1g showed no mortality in salinities of 0 & 7g/lit during t- test. Mortality of the juveniles weighting 0.2, 0.5 and 1g/1it increased during the first 12 hours and became constant to the end of the test. Mortality of juveniles weighting 0.2 & 0.5g in salinity of 16g/lit was similar to that of the juveniles weighting 0.2 & 0.5g in salinity of 12.5g/lit. Mortality of the juveniles increased significantly with increase of salinity and decreased with increase of weight (P<0.05)

NKX2-5 regulates the expression of beta-catenin and GATA4 in ventricular myocytes.

BackgroundThe molecular pathway that controls cardiogenesis is temporally and spatially regulated by master transcriptional regulators such as NKX2-5, Isl1, MEF2C, GATA4, and beta-catenin. The interplay between these factors and their downstream targets are not completely understood. Here, we studied regulation of beta-catenin and GATA4 by NKX2-5 in human fetal cardiac myocytes.Methodology/principal findingsUsing antisense inhibition we disrupted the expression of NKX2-5 and studied changes in expression of cardiac-associated genes. Down-regulation of NKX2-5 resulted in increased beta-catenin while GATA4 was decreased. We demonstrated that this regulation was conferred by binding of NKX2-5 to specific elements (NKEs) in the promoter region of the beta-catenin and GATA4 genes. Using promoter-luciferase reporter assay combined with mutational analysis of the NKEs we demonstrated that the identified NKX2-5 binding sites were essential for the suppression of beta-catenin, and upregulation of GATA4 by NKX2-5.ConclusionsThis study suggests that NKX2-5 modulates the beta-catenin and GATA4 transcriptional activities in developing human cardiac myocytes

Magnetic Branes in (n+1)(n+1)-dimensional Einstein-Maxwell-dilaton gravity

We construct two new classes of spacetimes generated by spinning and traveling magnetic sources in $(n+1)$-dimensional Einstein-Maxwell-dilaton gravity with Liouville-type potential. These solutions are neither asymptotically flat nor (A)dS. The first class of solutions which yields a $(n+1)$-dimensional spacetime with a longitudinal magnetic field and $k$ rotation parameters have no curvature singularity and no horizons, but have a conic geometry. We show that when one or more of the rotation parameters are nonzero, the spinning branes has a net electric charge that is proportional to the magnitude of the rotation parameters. The second class of solutions yields a static spacetime with an angular magnetic field, and have no curvature singularity, no horizons, and no conical singularity. Although one may add linear momentum to the second class of solutions by a boost transformation, one does not obtain a new solution. We find that the net electric charge of these traveling branes with one or more nonzero boost parameters is proportional to the magnitude of the velocity of the branes. We also use the counterterm method and calculate the conserved quantities of the solutions.Comment: 15 pages, the last version to appear in PR