Hopping Parameter Series Construction for Models with Nontrivial Vacuum

Hopping parameter expansions are convergent power series. Under general conditions they allow for the quantitative investigation of phase transition and critical behaviour. The critical information is encoded in the high order coefficients. Recently, 20th order computations have become feasible and used for a large class of lattice field models both in finite and infinite volume. They have been applied to quantum spin models and field theories at finite temperature. The models considered are subject to a global ${\bf Z}_2$ symmetry or to an even larger symmetry group such as O(N) with $N\geq 2$. In this paper we are concerned with the technical details of series computations to allow for a nontrivial vacuum expectation value $\not=0$, which is typical for models that break a global ${\bf Z}_2$ symmetry. Examples are scalar fields coupled to an external field, or manifestly gauge invariant effective models of Higgs field condensates in the electroweak theory, even in the high temperature phase. A nonvanishing tadpole implies an enormous proliferation of graphs and limits the graphical series computation to the 10th order. To achieve the hopping parameter series to comparable order as in the ${\bf Z}_2$ symmetric case, the graphical expansion is replaced by an expansion into new algebraic objects called vertex structures. In this way the 18th order becomes feasible.Comment: 19 pages, latex2

Dynamical Linked Cluster Expansions: A Novel Expansion Scheme for Point-Link-Point-Interactions

Dynamical linked cluster expansions are linked cluster expansions with hopping parameter terms endowed with their own dynamics. This amounts to a generalization from 2-point to point-link-point interactions. We develop an associated graph theory with a generalized notion of connectivity and describe an algorithmic generation of the new multiple-line graphs. We indicate physical applications to spin glasses, partially annealed neural networks and SU(N) gauge Higgs systems. In particular the new expansion technique provides the possibility of avoiding the replica-trick in spin glasses. We consider variational estimates for the SU(2) Higgs model of the electroweak phase transition. The results for the transition line, obtained by dynamical linked cluster expansions, agree quite well with corresponding high precision Monte Carlo results.Comment: 41 pages, latex2e, 10 postscript figure

Arguments for an additional long-lived intermediate in the photocycle of the full-length aureochrome 1c receptor: A time-resolved small-angle X-ray scattering study

Bannister S, Böhm E, Zinn T, Hellweg T, Kottke T. Arguments for an additional long-lived intermediate in the photocycle of the full-length aureochrome 1c receptor: A time-resolved small-angle X-ray scattering study. Structural Dynamics. 2019;6(3): 34701.Aureochromes (AUREO) act as blue-light photoreceptors in algae. They consist of a light-, oxygen-, voltage-sensitive (LOV) domain and a DNA-binding basic region/leucine zipper. Illumination of the flavin cofactor in LOV leads to the formation of an adduct, followed by global structural changes. Here, we first applied UV/vis spectroscopy to characterize the photocycle of full-length aureochrome 1c (PtAUREO1c) from the diatom Phaeodactylum tricornutum. With a time constant of 850 s and a quantum yield of 23%, PtAUREO1c reveals a faster recovery time and a much lower sensitivity toward light than PtAUREO1a, pointing to its role as a high light sensor in vivo. UV/vis spectroscopy offers details on the local recovery of the flavin chromophore. However, kinetic information on the global structural recovery of full-length AUREO or any other multidomain LOV protein is missing. This information is essential not least for the photoreceptors' applications as optogenetic devices. Therefore, we established a procedure to apply small-angle X-ray scattering on PtAUREO1c in a time-resolved manner employing an in-house setup. In combination with UV/vis spectroscopy under similar conditions, we revealed a discrepancy between the recovery of the global protein structure and the adduct lifetime. Accordingly, we propose to supplement the photocycle by an intermediate state (I447), which decays with a time constant of about 800 s and prolongs the lifetime of the signaling state

Shear recovery and temperature stability of Ca2+ and Ag+ glycolipid fibrillar metallogels with unusual β\beta-sheet-like domains

Low-molecular weight gelators (LMWG) are small molecules (Mw < ~1 kDa), which form self-assembled fibrillar networks (SAFiN) hydrogels in water. The great majority of SAFiN gels is described by an entangled network of self-assembled fibers, in analogy to a polymer in a good solvent. Here, fibrillation of a biobased glycolipid bolaamphiphile is triggered by Ca2+ or Ag+ ions, added to its diluted micellar phase. The resulting SAFiN, which forms hydrogel above 0.5 wt%, has a ``nano-fishnet'' structure, characterized by a fibrous network of both entangled fibers and $\beta$-sheets-like rafts, generally observed for silk fibroin, actin hydrogels or mineral imogolite nanotubes, but generally not known for SAFiN. This work focuses on the strength of the SAFIN gels, their fast recovery after applying a mechanical stimulus (strain) and their unusual resistance to temperature, studied by coupling rheology to small angle X-ray scattering (rheo-SAXS) using synchrotron radiation. The Ca2+-based hydrogel keeps its properties up to 55{\textdegree}C, while the Ag+-based gel shows a constant elastic modulus up to 70{\textdegree}C, without appearance of any gel-to-sol transition temperature. Furthermore, the glycolipid is obtained by fermentation from natural resources (glucose, rapeseed oil), thus showing that naturally-engineered compounds can have unprecedented properties, when compared to the wide range of chemically derived amphiphiles

The Rapidly Rotating, Hydrogen Deficient, Hot Post-Asymptotic Giant Branch Star ZNG 1 in the Globular Cluster M5

We report observations of the hot post-asymptotic giant branch star ZNG 1 in the globular cluster M5 (NGC 5904) with the Far Ultraviolet Spectroscopic Explorer (FUSE). From the resulting spectrum, we derive an effective temperature T_eff = 44300 +/- 300 K, a surface gravity log g = 4.3 +/- 0.1, a rotational velocity v sin i = 170 +/- 20 km/s, and a luminosity log (L/L_sun) = 3.52 +/- 0.04. The atmosphere is helium-rich (Y = 0.93), with enhanced carbon (2.6% by mass), nitrogen (0.51%) and oxygen (0.37%) abundances. The spectrum shows evidence for a wind with terminal velocity near 1000 km/s and an expanding shell of carbon- and nitrogen-rich material around the star. The abundance pattern of ZNG 1 is suggestive of the ``born-again'' scenario, whereby a star on the white-dwarf cooling curve undergoes a very late shell flash and returns to the AGB, but the star's rapid rotation is more easily explained by a previous interaction with a binary companion.Comment: 8 pages, 2 PostScript figures, Latex with emulateapj5. Accepted for publication in ApJ Letter

Encapsulated Zosteric Acid Embedded in Poly[3-hydroxyalkanoate] Coatings—Protection against Biofouling

Summary : The natural, non-toxic antifouling compound zosteric acid (ZA, p-coumaric acid sulfate) was encapsulated in polystyrene (PS) microcapsules (30 mg ZA /1 g PS) with an efficiency of 30 % via an in-liquid drying process. Electron micrographs showed microcapsules with smooth surfaces and a mean diameter of 200 μm. The FIB method was used to cross-section a microcapsule in order to visualize the inner capsule structure and to localize ZA via element analysis. Coatings of a biocompatible polyester, poly[3-hydroxyalkanoate-co-3-hydroxyalkenoate] (PHAE), were prepared on microscopic slides. These coatings contained dispersed ZA (PHAE/ZA) or ZA-loaded PS microcapsules (PHAE/PS(ZA)). The release of ZA was monitored via conductivy measurements in water and was 4 μgcm-2d-1 for PHAE/ZA and 0.9 μgcm-2d-1 for PHAE/PS(ZA) coatings. To follow the initial steps of biofilm formation, coated slides were exposed to activated sludge and analyzed for cell adhesion with ESEM. ZA was effective during the burst release time of the PHAE/ZA coating, but no significant differences in biofouling were observed after 48 h. This was attributed to the minimal effective release rate of ZA, which is approximately 10 μgcm-2d-

Application of Genetic Algorithms to Structure Elucidation of Halogenated Alkanes Considering the Corresponding 13C NMR Spectra

A new approach for structure elucidation using genetic algorithms is introduced. In analogy to the genetic programming paradigm developed by Koza, the new concept supports genetic operations on hierarchically coded chemical line notations. The implementation of this concept consists of 5 steps. In the first step, a start population of chemical compounds is randomly generated. As the second step, physical properties of each compound of the population are predicted. The third step is the comparison of each individual property with the observed property of an unknown compound, resulting in the calculation of the fitness value for each generated compound. Depending on the fitness values, the candidates for the next generation are selected by a spinning wheel procedure during the fourth step. In the last step, these candidates are rearranged by genetic mutation and crossover to form the next generation. Steps 2 to 5 of the described procedure are repeated until the spectrum of one candidate is almost equal to the spectrum of the unknown compound within acceptable tolerances. The introduced concept was verified for halogenated alkanes