1,799 research outputs found
Thick fluid disks around binary black holes
A model of a thick fluid disk around a binary black hole is considered. A
binary black hole is described by the Majumdar-Papapetrou solution. The
hydrodynamic equations in this metric are written out. Exact analytical
solutions are presented. Generalization to the case of a toroidal magnetic
field is carried out
Billiards with polynomial mixing rates
While many dynamical systems of mechanical origin, in particular billiards,
are strongly chaotic -- enjoy exponential mixing, the rates of mixing in many
other models are slow (algebraic, or polynomial). The dynamics in the latter
are intermittent between regular and chaotic, which makes them particularly
interesting in physical studies. However, mathematical methods for the analysis
of systems with slow mixing rates were developed just recently and are still
difficult to apply to realistic models. Here we reduce those methods to a
practical scheme that allows us to obtain a nearly optimal bound on mixing
rates. We demonstrate how the method works by applying it to several classes of
chaotic billiards with slow mixing as well as discuss a few examples where the
method, in its present form, fails.Comment: 39pages, 11 figue
Adatom incorporation and step crossing at the edges of 2D nanoislands
Adatom incorporation into the ``faceted'' steps bordering the 2D nanoislands
is analyzed. The step permeability and incorporation coefficients are derived
for some typical growth situations. It is shown that the step consisting of
equivalent straight segments can be permeable even in the case of fast egde
migration if there exist factors delaying creation of new kinks. The step
consisting of alternating rough and straight segments may be permeable if there
is no adatom transport between neighboring segments through the corner
diffusion.Comment: 3 pages, one figur
The wave function of a gravitating shell
We have calculated a discrete spectrum and found an exact analytical solution
in the form of Meixner polynomials for the wave function of a thin gravitating
shell in the Reissner-Nordstrom geometry. We show that there is no extreme
state in the quantum spectrum of the gravitating shell, as in the case of
extreme black hole.Comment: 7 pages, 1 figur
Development of the Vychegda-Vyatka-Kama drainage basin and changes in the outflow directions related to the Late-Glacial morphological conditions (North-Eastern European Russia)
The paper describes the features of the drainage system development in the upper Kama basin. Two buried river valleys were identified within the Kama-Pechora-Vychegda watershed. The upper courses of the Kama, the Vychegda, the Pechora and their tributaries likely belonged either to the White Sea basin, or the Caspian Basin. The southern direction of the outflow corresponded to the location of the palaeovalleys of the Pra-Kolva and the Pra-Vishera. The northern direction corresponded to the location of ancient hollows in the present valleys of the tributaries of the Kama. It is believed that the upper Kama was connected with the Vychegda basin. The geological structure of the palaeovalley has recorded a long period of joint development of the hydrosystems of the Kama and the Vyatka. The basins were divided only in the Late Neo-Pleistocene. The rivers regenerated in the Middle and Late Neo-Pleistocene after the lakes had flowed into the Kolva-Vishera basin in the east and into the Pra-Vyatka basin in the west
Possible types of the evolution of vacuum shells around the de Sitter space
All possible evolution scenarios of a thin vacuum shell surrounding the
spherically symmetric de Sitter space have been determined and the
corresponding global geometries have been constructed. Such configurations can
appear at the final stage of the cosmological phase transition, when isolated
regions (islands) of the old vacuum remain. The islands of the old vacuum are
absorbed by the new vacuum, expand unlimitedly, or form black holes and
wormholes depending on the sizes of the islands as well as on the density and
velocity of the shells surrounding the islands.Comment: 3 pages, 1 figur
Bacterial Phytochromes, Cyanobacteriochromes and Allophycocyanins as a Source of Near-Infrared Fluorescent Probes
Bacterial photoreceptors absorb light energy and transform it into intracellular signals that regulate metabolism. Bacterial phytochrome photoreceptors (BphPs), some cyanobacteriochromes (CBCRs) and allophycocyanins (APCs) possess the near-infrared (NIR) absorbance spectra that make them promising molecular templates to design NIR fluorescent proteins (FPs) and biosensors for studies in mammalian cells and whole animals. Here, we review structures, photochemical properties and molecular functions of several families of bacterial photoreceptors. We next analyze molecular evolution approaches to develop NIR FPs and biosensors. We then discuss phenotypes of current BphP-based NIR FPs and compare them with FPs derived from CBCRs and APCs. Lastly, we overview imaging applications of NIR FPs in live cells and in vivo. Our review provides guidelines for selection of existing NIR FPs, as well as engineering approaches to develop NIR FPs from the novel natural templates such as CBCRs.Peer reviewe
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