לוח שנה משולב

Cells use genetic switches to shift between alternate gene expression states, e.g. to adapt to new environments or to follow a developmental
pathway. Here, we study the dynamics of switching in a generic-feedback
on/off switch. Unlike protein-only models, we explicitly account for stochastic fluctuations of mRNA, which have a dramatic impact on switch dynamics. Employing a semi-classical theory to treat the underlying chemical master equations, we obtain accurate results for the quasi-stationary distributions of mRNA and protein copy numbers and for the mean switching time, starting from either state. Our analytical results agree well with extensive Monte Carlo simulations. Importantly, one can use the approach to study the effect of varying biological parameters on the switch stability.

This research is aimed to understanding plastic deformation mechanisms through the systematic analysis of the microstructure and dislocation patterns in deformed metals, mainly by electron microscopy techniques. Dislocation dynamics and microstructural evolution under applied stresses by means of in-situ experiments in the transmission electron microscope was performed in order to explore the mechanism of dislocation pattern formation.
The combined effect of strain and temperature on the microstructural evolution of plastically deformed fcc metals (Aluminum, Copper, Nickel and Gold) was examined systematically. In particular, the detailed nano-scale, internal structure of dislocation boundaries was determined. In all the metals studied, dislocations within the boundaries tend to rearrange themselves sequentially with increasing strain from tangles into dislocation cells with tangled boundaries, followed by the formation of dislocation boundaries consisting of wavy, parallel dislocations and finally into arrays of parallel dislocations. The results were represented by strain-temperature microstructural maps. The topology of the microstructural maps was found to be similar for all metals studied, suggesting a universal strain- temperature dependence in deformed fcc metals.
The experimental strain-temperature maps of dislocation structures at the nano-scale for the studied fcc metals are scaled by the cross-slip activation energy, calculated using an atomistic based elastic model, to form a single universal strain - temperature map. Such a map unifies many observations obtained by different groups over the years and serves to direct further investigations in this fundamental area. These implications for dislocation rearrangement mechanisms are discussed.

Xenon, as well as other noble gases, has been employed in recent years as a
target for direct detection of dark matter. There are many benefits in Xe
detectors, among which its scintillation properties, radiation stopping
power, particle discrimination, spatial resolution and scalability.

In this talk I will describe the currently running experiment XENON100,
located in LNGS, Italy, show the results of a recent measurement of the
scintillation properties of Xe at low recoil energies, and describe the
current efforts towards the next generation dark matter detector, XENON1T.

Aims: Recurrent nova systems like RS Oph have been proposed as a possible channel for type Ia supernova (SN) explosions based on the high mass of the accreting white dwarf. Additional support for this hypothesis has recently been provided by the detection of circumstellar material around SN 2006X and SN 2007le, showing a structure compatible with that expected for recurrent nova outbursts. We investigate the circumstellar environment of RS Oph and its structure with the aim of establishing a firmer and independent link between this class of objects and type Ia SN progenitors.
Methods: We study the time evolution of Ca ii, Na i, and K i absorption features in RS Oph before, during, and after the last outburst, using multi-epoch, high-resolution spectroscopy and applying the same method as was adopted for SN 2006X and SN 2007le.
Results: A number of components are detected , that are blue-shifted with respect to the systemic velocity of RS Oph. In particular, one feature strongly weakens in the first two weeks after the outburst, at the same time that the very narrow P-Cyg profiles disappear, which are overimposed on the much wider nova emission lines of H, He, Fe ii, and other elements.
Conclusions: We interpret this as the signature of density enhancements in the circumstellar material, suggesting that the recurrent eruptions might indeed create complex structures within the material lost by the donor star. This establishes a strong link between RS Oph and the progenitor system of the type Ia SN 2006X, for which similar features have been detected.
Based on observations obtained at ESO-La Silla.