Stable two-dimensional solitary pulses in linearly coupled dissipative Kadomtsev-Petviashvili equations

A two-dimensional (2D) generalization of the stabilized Kuramoto - Sivashinsky (KS) system is presented. It is based on the Kadomtsev-Petviashvili (KP) equation including dissipation of the generic (Newell -- Whitehead -- Segel, NWS) type and gain. The system directly applies to the description of gravity-capillary waves on the surface of a liquid layer flowing down an inclined plane, with a surfactant diffusing along the layer's surface. Actually, the model is quite general, offering a simple way to stabilize nonlinear waves in media combining the weakly-2D dispersion of the KP type with gain and NWS dissipation. Parallel to this, another model is introduced, whose dissipative terms are isotropic, rather than of the NWS type. Both models include an additional linear equation of the advection-diffusion type, linearly coupled to the main KP-NWS equation. The extra equation provides for stability of the zero background in the system, opening a way to the existence of stable localized pulses. The consideration is focused on the case when the dispersive part of the system of the KP-I type, admitting the existence of 2D localized pulses. Treating the dissipation and gain as small perturbations and making use of the balance equation for the field momentum, we find that the equilibrium between the gain and losses may select two 2D solitons, from their continuous family existing in the conservative counterpart of the model (the latter family is found in an exact analytical form). The selected soliton with the larger amplitude is expected to be stable. Direct simulations completely corroborate the analytical predictions.Comment: a latex text file and 16 eps files with figures; Physical Review E, in pres

Hyperpolarization-Activated Current (Ih) in Ganglion-Cell Photoreceptors

Intrinsically photosensitive retinal ganglion cells (ipRGCs) express the photopigment melanopsin and serve as the primary retinal drivers of non-image-forming visual functions such as circadian photoentrainment, the pupillary light reflex, and suppression of melatonin production in the pineal. Past electrophysiological studies of these cells have focused on their intrinsic photosensitivity and synaptic inputs. Much less is known about their voltage-gated channels and how these might shape their output to non-image-forming visual centers. Here, we show that rat ipRGCs retrolabeled from the suprachiasmatic nucleus (SCN) express a hyperpolarization-activated inwardly-rectifying current (Ih). This current is blocked by the known Ih blockers ZD7288 and extracellular cesium. As in other systems, including other retinal ganglion cells, Ih in ipRGCs is characterized by slow kinetics and a slightly greater permeability for K+ than for Na+. Unlike in other systems, however, Ih in ipRGCs apparently does not actively contribute to resting membrane potential. We also explore non-specific effects of the common Ih blocker ZD7288 on rebound depolarization and evoked spiking and discuss possible functional roles of Ih in non-image-forming vision. This study is the first to characterize Ih in a well-defined population of retinal ganglion cells, namely SCN-projecting ipRGCs

Prevalence of Cryptosporidium spp. in asymptomatic food workers.

Cryptosporidium spp. is obligatory intracellular parasite and causes intestinal infection. In intestine infections in the form of sporadic and epidemics, food and accordingly workers in food sector may play a role as the source of infection. In this study, it is aimed to reveal the existence of asymptomatic cryptosporidiosis. In the study, stool samples of 393 workers -employed at various branches of food sector in the region of Van- are used. In order to detect Cryptosporidium spp. oocysts, Modified Ziehl Neelsen (MZN) Staining was used. In this study, asymptomatic cryptosporidiosis has been detected in 5 (1.27%) of 393 workers. Epidemiological findings indicate that food workers can be source of cryptosporidiosis outbreak. Thus, searching for the existence of asymptomatic cryptosporidiosis food workers -which epidemiologically has potential significance- and taking the required measures in case of its determination are significant in respect of public health

European citizenship and European Union expansion: Perspectives on Europeanness and citizenship education from Britain and Turkey

This article discusses some perspectives on citizenship education in Turkey and Britain in the context of current contested discourses on the nature of European identity and of the European Union (EU). It is based on data collected during an EU-funded student teacher exchange programme between three universities in Turkey and Leicester University in the United Kingdom. The programme facilitated participants’ investigations of their understandings of citizenship and citizenship education in Britain and Turkey. Data was collected by questionnaire from 581 Turkish student teachers and 85 British student teachers involved with citizenship education and, during the exchange visits, through focus group interviews with 14 British and 14 Turkish students. Both groups thought citizenship education was key to creating ‘good citizens’ in their countries, but the nature of this citizenship was perceived to differ between countries. The Turkish students placed a strong emphasis on national identity and Turkish citizenship, whilst the British students focused more on democracy, social justice, global citizenship and human rights. Students from both countries questioned the efficacy of the pedagogical approaches that they observed during school visits in each other’s countries