Photosynthesis is widely distributed among Proteobacteria as demonstrated by the phylogeny of PufLM reaction center proteins

Two different photosystems for performing bacteriochlorophyll-mediated photosynthetic energy conversion are employed in different bacterial phyla. Those bacteria employing a photosystem II type of photosynthetic apparatus include the phototrophic purple bacteria (Proteobacteria), Gemmatimonas and Chloroflexus with their photosynthetic relatives. The proteins of the photosynthetic reaction center PufL and PufM are essential components and are common to all bacteria with a type-II photosynthetic apparatus, including the anaerobic as well as the aerobic phototrophic Proteobacteria. Therefore, PufL and PufM proteins and their genes are perfect tools to evaluate the phylogeny of the photosynthetic apparatus and to study the diversity of the bacteria employing this photosystem in nature. Almost complete pufLM gene sequences and the derived protein sequences from 152 type strains and 45 additional strains of phototrophic Proteobacteria employing photosystem II were compared. The results give interesting and comprehensive insights into the phylogeny of the photosynthetic apparatus and clearly define Chromatiales, Rhodobacterales, Sphingomonadales as major groups distinct from other Alphaproteobacteria, from Betaproteobacteria and from Caulobacterales (Brevundimonas subvibrioides). A special relationship exists between the PufLM sequences of those bacteria employing bacteriochlorophyll b instead of bacteriochlorophyll a. A clear phylogenetic association of aerobic phototrophic purple bacteria to anaerobic purple bacteria according to their PufLM sequences is demonstrated indicating multiple evolutionary lines from anaerobic to aerobic phototrophic purple bacteria. The impact of pufLM gene sequences for studies on the environmental diversity of phototrophic bacteria is discussed and the possibility of their identification on the species level in environmental samples is pointed out. © 2018 Imhoff, Rahn, Künzel and Neulinger

Strong (π,0)(\pi,0) spin fluctuations in β\beta-FeSe observed by neutron spectroscopy

We have performed powder inelastic neutron scattering measurements on the unconventional superconductor $\beta$-FeSe ($T_{\rm c} \simeq 8\,\mathrm{K}$). The spectra reveal highly dispersive paramagnetic fluctuations emerging from the square-lattice wave vector $(\pi,0)$ extending beyond 80 meV in energy. Measurements as a function of temperature at an energy of $\sim 13\,\mathrm{meV}$ did not show any variation from $T_{\rm c}$ to $104\,\mathrm{K}$. The results show that FeSe is close to an instability towards $(\pi,0)$ antiferromagnetism characteristic of the parent phases of the high-$T_{\rm c}$ iron arsenide superconductors, and that the iron paramagnetic moment is neither affected by the orthorhombic-to-tetragonal structural transition at $T_{\rm s} \simeq 90\,\mathrm{K}$ nor does it undergo a change in spin state over the temperature range studied.Comment: Revised version, includes Supplementary Materia

Positionally dependent ^(15)N fraction factors in the UV photolysis of N_2O determined by high resolution FTIR spectroscopy

Positionally dependent fractionation factors for the photolysis of isotopomers of N_2O in natural abundance have been determined by high resolution FTIR spectroscopy at three photolysis wavelengths. Fractionation factors show clear 15N position and photolysis wavelength dependence and are in qualitative agreement with theoretical models but are twice as large. The fractionation factors increase with photolysis wavelength from 193 to 211 nm, with the fractionation factors at 207.6 nm for ^(14)N^(15)N^916)O, ^(15)N^(14)N^(16)O and ^(14)N^(14)N^(18)O equal to −66.5±5‰,−27.1±6‰ and −49±10‰, respectively

Versatile module for experiments with focussing neutron guides

We report the development of a versatile module that permits fast and reliable use of focussing neutron guides under varying scattering angles. A simple procedure for setting up the module and neutron guides is illustrated by typical intensity patterns to highlight operational aspects as well as typical parasitic artefacts. Combining a high-precision alignment table with separate housings for the neutron guides on kinematic mounts, the change-over between neutron guides with different focussing characteristics requires no readjustments of the experimental set-up. Exploiting substantial gain factors, we demonstrate the performance of this versatile neutron scattering module in a study of the effects of uniaxial stress on the domain populations in the transverse spin density wave phase of single crystal Cr

On Linear Congestion Games with Altruistic Social Context

We study the issues of existence and inefficiency of pure Nash equilibria in linear congestion games with altruistic social context, in the spirit of the model recently proposed by de Keijzer {\em et al.} \cite{DSAB13}. In such a framework, given a real matrix $\Gamma=(\gamma_{ij})$ specifying a particular social context, each player $i$ aims at optimizing a linear combination of the payoffs of all the players in the game, where, for each player $j$, the multiplicative coefficient is given by the value $\gamma_{ij}$. We give a broad characterization of the social contexts for which pure Nash equilibria are always guaranteed to exist and provide tight or almost tight bounds on their prices of anarchy and stability. In some of the considered cases, our achievements either improve or extend results previously known in the literature

Machine Protection Considerations for BERLinPro

The Berlin energy recovery linac project BERLinPro at the HZB is a 50 MeV ERL test facility, which addresses physical and technological questions for future superconducting rf based high brightness, high current electron beam sources. The combination of a 100 mA cw beam, electron bunches with normalized emittances lower than 1 mm mrad and the magnet optics of BERLinPro leads to power densities capable to harm the accelerator components within microseconds if total beam loss occurs. Furthermore, continuous beam loss on the level of 10 5 has to be controlled to avoid activation and to protect the SRF, beam diagnostics and other infrastructure components. In this paper, we present the evaluation of the required key parameters of the BERLinPro machine protection system and present its first conceptual desig

Finite temperature quantum simulation of stabilizer Hamiltonians

We present a scheme for robust finite temperature quantum simulation of stabilizer Hamiltonians. The scheme is designed for realization in a physical system consisting of a finite set of neutral atoms trapped in an addressable optical lattice that are controllable via 1- and 2-body operations together with dissipative 1-body operations such as optical pumping. We show that these minimal physical constraints suffice for design of a quantum simulation scheme for any stabilizer Hamiltonian at either finite or zero temperature. We demonstrate the approach with application to the abelian and non-abelian toric codes.Comment: 13 pages, 2 figure