Structures and waves in a nonlinear heat-conducting medium

The paper is an overview of the main contributions of a Bulgarian team of researchers to the problem of finding the possible structures and waves in the open nonlinear heat conducting medium, described by a reaction-diffusion equation. Being posed and actively worked out by the Russian school of A. A. Samarskii and S.P. Kurdyumov since the seventies of the last century, this problem still contains open and challenging questions.Comment: 23 pages, 13 figures, the final publication will appear in Springer Proceedings in Mathematics and Statistics, Numerical Methods for PDEs: Theory, Algorithms and their Application

Optimized production of large Bose Einstein Condensates

We suggest different simple schemes to efficiently load and evaporate a ''dimple'' crossed dipolar trap. The collisional processes between atoms which are trapped in a reservoir load in a non adiabatic way the dimple. The reservoir trap can be provided either by a dark SPOT Magneto Optical Trap, the (aberrated) laser beam itself or by a quadrupolar or quadratic magnetic trap. Optimal parameters for the dimple are derived from thermodynamical equations and from loading time, including possible inelastic and Majorana losses. We suggest to load at relatively high temperature a tight optical trap. Simple evaporative cooling equations, taking into account gravity, the possible occurrence of hydrodynamical regime, Feshbach resonance processes and three body recombination events are given. To have an efficient evaporation the elastic collisional rate (in s$^{-1}$) is found to be on the order of the trapping frequency and lower than one hundred times the temperature in micro-Kelvin. Bose Einstein condensates with more than $10^7$ atoms should be obtained in much less than one second starting from an usual MOT setup.Comment: 14 page

Dynamics of non-equilibrium membrane bud formation

The dynamical response of a lipid membrane to a local perturbation of its molecular symmetry is investigated theoretically. A density asymmetry between the two membrane leaflets is predominantly released by in-plane lipid diffusion or membrane curvature, depending upon the spatial extent of the perturbation. It may result in the formation of non-equilibrium structures (buds), for which a dynamical size selection is observed. A preferred size in the micrometer range is predicted, as a signature of the crossover between membrane and solvent dominated dynamical membrane response.Comment: 7 pages 3 figure

A pump-probe study of the formation of rubidium molecules by ultrafast photoassociation of ultracold atoms

An experimental pump-probe study of the photoassociative creation of translationally ultracold rubidium molecules is presented together with numerical simulations of the process. The formation of loosely bound excited-state dimers is observed as a first step towards a fully coherent pump-dump approach to the stabilization of Rb$_2$ into its lowest ground vibrational states. The population that contributes to the pump-probe process is characterized and found to be distinct from a background population of pre-associated molecules.Comment: Accepted for publication in Phys. Rev. A (10 pages, 9 figures

Some additional properties of elementary landscapes

AbstractIn this work, we derive a general class of multistep composite elementary landscapes and present the first non-trivial lower (upper) bounds on local minima (maxima) associated with elementary landscapes

Tinnitus – a manifestation of neurodegenerative diseases

BackgroundTinnitus is a widespread hearing impairment that can be characterized by the perception of sound, such as tone or noise, in the absence of an appropriate external sound source. The cause of tinnitus and mechanism are unclear. The prevalence of tinnitus is higher in people over 60 years of age. Tinnitus is usually a manifestation of а hearing impairment. Symptoms can be acute or chronic. In most cases, tinnitus manifests as an idiopathic condition. In the clinical practice, common factors that affect the psychological and emotional well-being of people with tinnitus are: fear, stress, anxiety and depression, which in turn can cause insomnia, impaired concentration and cognitive dysfunction. Tinnitus is a heterogeneous disorder in terms of its etiology and clinic. Tinnitus is associated with hearing loss, as both symptoms often occur together, though in many clinical cases, people with hearing loss do not develop tinnitus.MethodsWe present а clinical case of a patient diagnosed with a posturographic system, along with a full otoneurological and hearing examinations. Methods of videonystagmography, video head impulse test, subjective visual vertical, audiometry, tympanometry, otoacoustic emissions test, automated auditory brainstem response were used. We provided a dental check-up and an occlusion analysis. Patient filled out questionnaires and signed a written informed consent. The aim of the team was to analyze the manifestation of tinnitus as a precursor of a neurodegenerative disease.Results and discussionFrom the literature review done chronic tinnitus is associated with anatomical brain abnormalities, including decreased cortical gray matter and decreased white matter integrity. There is also a high prevalence of cognitive impairment reported among patients with tinnitus from a clinical point of view. Tinnitus is an independent risk factor for subsequent neurodegenerative disease. There are a number of neurological conditions that can be encountered in the otorhinolaryngological and dental practice. It is important for the dentist to enrich own knowledge of the underlying neurological conditions, as they may affect the provision of dental treatment. Our findings from the examinations executed are consistent with previous studies, which show that diabetes and head injuries can be risk factors for AD and neurodegeneration.ConclusionsFurther research is needed to re-confirm the conclusions of our research and to investigate the pathophysiology of the relationship between tinnitus and the Alzheimer’s disease and tinnitus and the Parkinson’s disease in more depth