Divergent roles of CprK paralogues from Desulfitobacterium hafniense in activating gene expression

Gene duplication and horizontal gene transfer play an important role in the evolution of prokaryotic genomes. We have investigated the role of three CprK paralogues from the cAMP receptor protein-fumarate and nitrate reduction regulator (CRP-FNR) family of transcriptional regulators that are encoded in the genome of Desulfitobacterium hafniense DCB-2 and possibly regulate expression of genes involved in the energy-conserving terminal reduction of organohalides (halorespiration). The results from in vivo and in vitro promoter probe assays show that two regulators (CprK1 and CprK2) have an at least partially overlapping effector specificity, with preference for ortho-chlorophenols, while meta-chlorophenols proved to be effectors for CprK4. The presence of a potential transposase-encoding gene in the vicinity of the cprK genes indicates that their redundancy is probably caused by mobile genetic elements. The CprK paralogues activated transcription from promoters containing a 14 bp inverted repeat (dehalobox) that closely resembles the FNR-box. We found a strong negative correlation between the rate of transcriptional activation and the number of nuclecitide changes from the optimal dehalobox sequence (TTAAT-N-4-ATTAA). Transcription was initiated by CprK4 from a promoter that is situated upstream of a gene encoding a methyl-accepting chemotaxis protein. This might be the first indication of taxis of an anaerobic bacterium to halogenated aromatic compounds

On the Azimuthal Stability of Shock Waves around Black Holes

Analytical studies and numerical simulations of time dependent axially symmetric flows onto black holes have shown that it is possible to produce stationary shock waves with a stable position both for ideal inviscid and for moderately viscous accretion disks. We perform several two dimensional numerical simulations of accretion flows in the equatorial plane to study shock stability against non-axisymmetric azimuthal perturbations. We find a peculiar new result. A very small perturbation seems to produce an instability as it crosses the shock, but after some small oscillations, the shock wave suddenly transforms into an asymmetric closed pattern, and it stabilizes with a finite radial extent, despite the inflow and outflow boundary conditions are perfectly symmetric. The main characteristics of the final flow are: 1) The deformed shock rotates steadily without any damping. It is a permanent feature and the thermal energy content and the emitted energy vary periodically with time. 2) This behavior is also stable against further perturbations. 3) The average shock is still very strong and well defined, and its average radial distance is somewhat larger than that of the original axially symmetric circular shock. 4) Shocks obtained with larger angular momentum exhibit more frequencies and beating phenomena. 5) The oscillations occur in a wide range of parameters, so this new effect may have relevant observational consequences, like (quasi) periodic oscillations, for the accretion of matter onto black holes. Typical time scales for the periods are 0.01 and 1000 seconds for black holes with 10 and 1 million solar mass, respectively.Comment: 15 pages, 7 figures, accepted by the Astrophysical Journa

Cumulative Surface Location Error for Milling Processes Based on Tool-tip Frequency Response Function

AbstractIn milling processes, the desired machined surface cannot be perfectly achieved even in case of chatter-free machining due to the thermally induced errors, the trajectory following errors and the most significant one: the cutting force induced vibration errors. In case of vibration, the error is represented by the so-called Surface Location Error (SLE), which is the distance between the machined and the required surface position. In case of roughing operations, these errors can have a significant impact on the surface position due to the interaction between the subsequent SLEs. The machined surface depends on the previously resulted SLE through the variation of the radial immersion. In this paper, the series of the consecutive SLEs are investigated in a multi-degree-of-freedom model. The dynamical behaviour of the milling tool is described by frequency response functions. The variation of the SLE values is governed by a discrete map, which may lead to an unpredictable final surface position. The parameter range where this unpredictable final SLE occurs is presented together with the traditional stability chart representing the chatter-free domains of cutting parameters. With the proposed methods, the traditional stability chart can be improved, from which chatter-free and CSLE-stable technological parameters can be selected

Total Synthesis of Tulearin C

With the help of the smaller brother: Although alkyne metathesis will always be the little brother of alkene metathesis, it allows problems to be solved that are currently beyond reach of the more famous sibling. This notion is exemplified by the tulearin macrolides, which could only be selectively forged by ring-closing alkyne metathesis (RCAM)/trans reduction using the latest generation of alkyne metathesis catalysts

Acoustic characterization of Hofstadter butterfly with resonant scatterers

We are interested in the experimental characterization of the Hofstadter butterfly by means of acoustical waves. The transmission of an acoustic pulse through an array of 60 variable and resonant scatterers periodically distribued along a waveguide is studied. An arbitrary scattering arrangement is realized by using the variable length of each resonator cavity. For a periodic modulation, the structures of forbidden bands of the transmission reproduce the Hofstadter butterfly. We compare experimental, analytical, and computational realizations of the Hofstadter butterfly and we show the influence of the resonances of the scatterers on the structure of the butterfly

Atom holography

We study the conditions under which atomic condensates can be used as a recording media and then suggest a reading scheme which allows to reconstruct an object with atomic reading beam. We show that good recording can be achieved for flat condensate profiles and for negative detunings between atomic Bohr frequency and optical field frequency. The resolution of recording dramatically depends on the relation between the healing length of the condensate and the spatial frequency contents of the optical fields involved.Comment: 8 pages, 5 figures, Late

A preliminary assessment of water partitioning and ecohydrological coupling in northern headwaters using stable isotopes and conceptual runoff models

Funded by European Research Council ERC. Grant Number: GA 335910 VEWA Swedish Science Foundation (SITES) Future Forest Formas (ForWater) SKB the Kempe foundation Environment Canada the Garfield Weston Foundation the Natural Sciences and Engineering Research Council of Canada (NSERC) the Northwest Territories Cumulative Impacts Monitoring ProgramPeer reviewedPublisher PD