First results from the OSQAR photon regeneration experiment: No light shining through a wall

A new method to amplify the photon-axion conversions in magnetic field is proposed using a buffer gas at a specific pressure. As a first result, new bounds for mass and coupling constant for purely laboratory experiments aiming to detect any hypothetical scalars and pseudo-scalars which can couple to photons were obtained at 95% confidence level, excluding the PVLAS result newly disclaimed.Comment: 4 pages, 5 figure

First Results of the Full-Scale OSQAR Photon Regeneration Experiment

Recent intensive theoretical and experimental studies shed light on possible new physics beyond the standard model of particle physics, which can be probed with sub-eV energy experiments. In the second run of the OSQAR photon regeneration experiment, which looks for the conversion of photon to axion (or Axion-Like Particle), two spare superconducting dipole magnets of the Large Hadron Collider (LHC) have been used. In this paper we report on first results obtained from a light beam propagating in vacuum within the 9 T field of two LHC dipole magnets. No excess of events above the background was detected and the two-photon couplings of possible new scalar and pseudo-scalar particles could be constrained.Comment: 5 pages, 4 figures, Photon 2011 Conference, Submitted to JO

Robust Organizational Principles of Protrusive Biopolymer Networks in Migrating Living Cells

Cell migration is associated with the dynamic protrusion of a thin actin-based cytoskeletal extension at the cell front, which has been shown to consist of two different substructures, the leading lamellipodium and the subsequent lamellum. While the formation of the lamellipodium is increasingly well understood, organizational principles underlying the emergence of the lamellum are just beginning to be unraveled. We report here on a 1D mathematical model which describes the reaction-diffusion processes of a polarized actin network in steady state, and reproduces essential characteristics of the lamellipodium-lamellum system. We observe a steep gradient in filament lengths at the protruding edge, a local depolymerization maximum a few microns behind the edge, as well as a differential dominance of the network destabilizer ADF/cofilin and the stabilizer tropomyosin. We identify simple and robust organizational principles giving rise to the derived network characteristics, uncoupled from the specifics of any molecular implementation, and thus plausibly valid across cell types. An analysis of network length dependence on physico-chemical system parameters implies that to limit array treadmilling to cellular dimensions, network growth has to be truncated by mechanisms other than aging-induced depolymerization, e.g., by myosin-associated network dissociation at the transition to the cell body. Our work contributes to the analytical understanding of the cytoskeletal extension's bisection into lamellipodium and lamellum and sheds light on how cells organize their molecular machinery to achieve motility

Membranove a transportni poruchy u experimentalni hypertenze.

An attempt was made to analyze the role of membrane abnormalities and ion transport alterations in the pathogenetic mechanisms governing the development and maintenance of high blood pressure in experimental hypertension. A special attention was paid to the differences between animals which were influenced by the hypertensive stimuli (namely high salt intake) in prepuberty or only in adulthood. 1. High salt intake in prepuberty and puberty is a necessary prerequisite for cliciting severe self-sustaining forms of experimental hypertension. Young salt hypertensive rats are characterized not only by a greater rise in systemic resistance but also by the reduction in arterial compliance. 2. There is a different participation of vasoactive factors in the maintenance of blood pressure in rats with salt-dependent hypertension elicited in youth or in adulthood. The influence of sympathetic nervous system and endogenous digoxin-like factor (DLF) is augmented in young salt hypertensive animals, whereas vasoconstrictor effects of vasopressin and angiotensin II are enhanced in rats subjected to the same hypertensive stimuli in adulthood only.Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Developmental windows and environment as important factors in the expression of genetic information: a cardiovascular physiologist’s view. Clin Sci (Lond) 2006, 111(5):295–305.Competing interests The authors declare that they have no competing interests.

A B S T R A C T Genetic studies in humans and rodent models should help to identify altered genes important in the development of cardiovascular diseases, such as hypertension. Despite the considerable research effort, it is still difficult to identify all of the genes involved in altered blood pressure regulation thereby leading to essential hypertension. We should keep in mind that genetic hypertension and other cardiovascular diseases might develop as a consequence of early errors in well-co-ordinated systems regulating cardiovascular homoeostasis. If these early abnormalities in the ontogenetic cascade of expression of genetic information occur in critical periods of development (developmental windows), they can adversely modify subsequent development of the cardiovascular system. The consideration that hypertension and/or other cardiovascular diseases are late consequences of abnormal ontogeny of the cardiovascular system could explain why so many complex interactions among genes and environmental factors play such a significant role in the pathogenesis of these diseases. The detailed description and precise time resolution of major developmental events occurring during particular stages of ontogeny in healthy individuals (including advanced knowledge of gene expression) could facilitate the detection of abnormalities crucial for the development of cardiovascular alterations characteristic of the respective diseases. Transient gene switch-on or switch-off in specific developmental windows might be a useful approach for in vivo modelling of pathological processes. This should help to elucidate the mechanisms underlying cardiovascular diseases (including hypertension) and to develop strategies to prevent the development of such diseases