A new deep-bodied Late Permian actinopterygian fish from the Beaufort Group, South Africa

Anew genus of actinopterygian (ray-finned) fish, Blourugia seeleyi is described from Late Permian (Tatarian) fluvio-lacustrine, siltstone dominated deposits within the lower Beaufort Group of South Africa. It was originally provisionally assigned to the globally known genus Atherstonia by Woodward (1893), but indications are that the genus is distinct from Atherstonia on the basis of its deep-bodied form and the associated skull characters; thus Blourugia seeleyi is placed in Gardiner&Schaeffer’s (1989) Platysomus Group. The new genus is characterized by a uniquely shaped prominent high triangular posterior blade of the maxilla, dermosphenotic triangular shaped, pointed marginal teeth, 8–10 branchiostegal rays, flank scales that exhibit a well-developed dermal ornamentation consisting of numerous transverse ganoine ridges, and the presence of a dermopterotic that contacts the nasal. Blourugia appears to be a primitive deep-bodied form, basal to lower actinopterygian deep-bodied forms such as Adroichthys, Amphicentrum, Cheirodopsis, Paramesolepis and Platysomus. As a member of Gardiner & Schaeffer’s Platysomus Group, it is therefore derived relative to stem-actinopterans such as Howqualepis, Mimia and Moythomasia, and also derived relative to earlier southern African Palaeozoic actinopterygians such as Atherstonia scutata, Mentzichthys jubbi, Namaichthys schroederi and the newly/recently described lower Beaufort Group taxa Bethesdaichthys kitchingi and Kompasia delaharpei, but basal to stem-neopterygians such as Australosomus and Saurichthys.South African Council for Geoscienc

A new late Permian ray-finned (actinopterygian) fish from the Beaufort Group, South Africa

Main articleA new genus and species of actinopterygian (ray-finned) fish, Kompasia delaharpei, is described from Late Permian (Tatarian) fluvio-lacustrine, siltstone dominated deposits within the lower Beaufort Group of South Africa. It is currently known from two localities on adjoining farms, Wilgerbosch and Ganora, both in the New Bethesda district of the Eastern Cape Karoo region. The fossils were recovered from an uncertain formation, possibly closely equivalent to the Balfour Formation, within the Dicynodon Assemblage Zone. Kompasia delaharpei differs from previously described early actinopterygians, including the recently described new lower Beaufort Group taxon Bethesdaichthys kitchingi, on the basis of a combination of skull and post cranial characters. The genus is characterised by: a uniquely shaped subrectangular posterior blade of the maxilla, a shortened dorsal limb of the preopercular, and a dermopterotic and dermosphenotic contacting the nasal; furthermore, the subopercular is equal to or longer than the opercular, the dorsal fin is situated in the posterior third of the body, slightly behind the position of the anal fin, and the anterior midflank scales exhibit a smooth dermal pattern or surface, with a number of faint ganoine ridges present parallel to the posterior and ventral scale margins. Kompasia appears to exhibit a relatively conservative morphology similar to that in the lower Beaufort Group taxon Bethesdaichthys kitchingi. As such, Kompasia is derived relative to stem-actinopterans such as Howqualepis, Mimia and Moythomasia, and also derived relative to earlier southern African Palaeozoic actinopterygians such as Mentzichthys jubbi and Namaichthys schroederi, but basal to stem-neopterygians such as Australosomus and Saurichthys.Palaeo-Anthropology Scientific Trust; French Embassy in South Africa; Co-operation and Cultural Service

A variational Monte Carlo algorithm for lattice gauge theories with continuous gauge groups: a study of (2+1)-dimensional compact QED with dynamical fermions at finite density

Lattice gauge theories coupled to fermionic matter account for many interesting phenomena in both high energy physics and condensed matter physics. Certain regimes, e.g. at finite fermion density, are difficult to simulate with traditional Monte Carlo algorithms due to the so-called sign-problem. We present a variational, sign-problem-free Monte Carlo method for lattice gauge theories with continuous gauge groups and apply it to (2+1)-dimensional compact QED with dynamical fermions at finite density. The variational ansatz is formulated in the full gauge field basis, i.e. without having to resort to truncation schemes for the $U(1)$ gauge field Hilbert space. The ansatz consists of two parts: first, a pure gauge part based on Jastrow-type ansatz states (which can be connected to certain neural-network ansatz states) and secondly, on a fermionic part based on gauge-field dependent fermionic Gaussian states. These are designed in such a way that the gauge field integral over all fermionic Gaussian states is gauge-invariant and at the same time still efficiently tractable. To ensure the validity of the method we benchmark the pure gauge part of the ansatz against another variational method and the full ansatz against an existing Monte Carlo simulation where the sign-problem is absent. Moreover, in limiting cases where the exact ground state is known we show that our ansatz is able to capture this behavior. Finally, we study a sign-problem affected regime by probing density-induced phase transitions.Comment: 14+6 pages, 9+1 figure

Real-time dynamics in 2+1d compact QED using complex periodic Gaussian states

We introduce a class of variational states to study ground state properties and real-time dynamics in (2+1)-dimensional compact QED. These are based on complex Gaussian states which are made periodic in order to account for the compact nature of the $U(1)$ gauge field. Since the evaluation of expectation values involves infinite sums, we present an approximation scheme for the whole variational manifold. We calculate the ground state energy density for lattice sizes up to $20 \times 20$ and extrapolate to the thermodynamic limit for the whole coupling region. Additionally, we study the string tension both by fitting the potential between two static charges and by fitting the exponential decay of spatial Wilson loops. As the ansatz does not require a truncation in the local Hilbert spaces, we analyze truncation effects which are present in other approaches. The variational states are benchmarked against exact solutions known for the one plaquette case and exact diagonalization results for a $\mathbb{Z}_3$ lattice gauge theory. Using the time-dependent variational principle, we study real-time dynamics after various global quenches, e.g. the time evolution of a strongly confined electric field between two charges after a quench to the weak-coupling regime. Up to the points where finite size effects start to play a role, we observe equilibrating behavior.Comment: 20 pages, 16 figures, v2: as publishe

Engineering long-range molecular potentials by external drive

We report the engineering of molecular potentials at large interatomic distances. The molecular states are generated by off-resonant optical coupling to a highly excited, long-range Rydberg molecular potential. The coupling produces a potential well in the low-lying molecular potential, which supports a bound state. The depth of the potential well, and thus the binding energy of the molecule, can be tuned by the coupling parameters. We characterize these molecules and find good agreement with a theoretical model based on the coupling of the two involved adiabatic potential energy curves. Our results open numerous possibilities to create long-range molecules between ultracold ground state atoms and to use them for ultracold chemistry and applications such as Feshbach resonances, Efimov physics or the study of halo molecules

Genetic Analysis of Putative Familial Relationships in a Captive Chimpanzee (Pan troglodytes) Population

Twelve autosomal dinucleotide repeat loci were analyzed in chimpanzees genomes by DNA amplification using primers designed for analysis of human loci. The markers span the entire length of human chromosomes 21 and 22. Nine markers were polymorphic in chimpanzee as well, with a somewhat comparable level of polymorphism and allele size range. Even in the presence of very limited information and in spite of missing samples, it was possible to reconstruct a complex pedigree and to provide molecular data that corroborate family relationships that were deduced from cage history and behavioral data. The conclusions were further supported by mitochondrial DNA analysis. The data presented in this report show that the extremely abundant source of human markers may be exploited to validate, with molecular evidence, hypotheses on individual relationship or alleged pedigrees, based upon behavioral observations

Griffiths Phase in a Facilitated Rydberg Gas at Low Temperature

The spread of excitations by Rydberg facilitation bears many similarities to epidemics. Such systems can be modeled with Monte-Carlo simulations of classical rate equations to great accuracy as a result of high dephasing. In this paper, we analyze the dynamics of a Rydberg many-body system in the facilitation regime in the limits of high and low temperatures. While in the high-temperature limit a homogeneous mean-field behaviour is recovered, characteristic effects of heterogeneity can be seen in a frozen gas. At large temperatures the system displays an absorbing-state phase transition and, in the presence of an additional loss channel, self-organized criticality. In a frozen or low-temperature gas, excitations are constrained to a network resembling an Erd\"os-Renyi graph. We show that the absorbing-state phase transition is replaced with an extended Griffiths phase, which we accurately describe by a susceptible-infected-susceptible model on the Erd\"os-Renyi network taking into account Rydberg blockade. Furthermore, we expand upon an existing macroscopic Langevin equation to more accurately describe the density of Rydberg atoms in the frozen and finite temperature regimes.Comment: 14 pages, 11 figure

Experimental realization of a 3D long-range random hopping model

Randomness and disorder have strong impact on transport processes in quantum systems and give rise to phenomena such as Anderson localization [1-3], many-body localization [4] or glassy dynamics [5]. Their characteristics thereby depend on the strength and type of disorder. An important class are hopping models, where particles or excitations move through a system which has randomized couplings. This includes, e.g., spin glasses [5], coupled optical waveguides [6], or NV center arrays [7]. They are also key to understand excitation transport in molecular and biological systems, such as light harvesting complexes [8]. In many of those systems, the microscopic coupling mechanism is provided by the dipole-dipole interaction. Rydberg systems [9] are therefore a natural candidate to study random hopping models. Here, we experimentally study a three-dimensional many-body Rydberg system with random dipole-dipole couplings. We measure the spectrum of the many-body system and find good agreement with an effective spin model. We also find spectroscopic signatures of a localization-delocalization transition. Our results pave the way to study transport processes and localization phenomena in random hopping models in detail. The inclusion of strong correlations is experimentally straightforward and will allow to study the interplay between random hopping and localization in strongly interacting systems.Comment: 7 pages, 4 figure

Non-unions treated with bone morphogenic protein 7: introducing the quantitative measurement of human serum cytokine levels as promising tool in evaluation of adjunct non-union therapy

Background: In this study we sought to determine if application of bone morphogenic protein 7 (BMP-7) promotes physiological bone healing of non-unions and to investigate if serum cytokine analysis may serve as a promising tool in the analysis of adjunct non-union therapy. Therefore we analyzed the influence of BMP-7 application on the serum cytokine expression patterns on patients with impaired bone healing compared to patients that showed proper bone healing. Methods: Our study involved analyzing blood samples from 208 patients with long bone fractures together with patients that subsequently developed non-unions. From this large pool, 15 patients with atrophic non-union were matched to 15 patients with atrophic non-union treated with local application of BMP-7 as well as normal bone healing. Changes in the cytokine expression patterns were monitored during the 1st, 2nd, 4th, 8th, 12th and 52nd week. The patients were followed both clinically and radiologically for the entire duration of the study. Serum cytokine expression levels of transforming growth factor beta (TGF-β), platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) were analyzed and compared. Results: Serum expression of TGF-β were nearly parallel in all three groups, however serum concentrations were significantly higher in patients with proper bone healing and those treated with BMP-7 than in patients with non-unions (p < 0.05). bFGF serum concentrations increased initially in patients with proper bone healing and in those treated with BMP-7. Afterwards, values decreased; bFGF serum concentrations in the BMP-7 group were significantly higher than in the other groups (p < 0.05). PDGF serum concentration levels were nearly parallel in all groups, serum concentrations were significantly higher in patients with proper bone healing and those treated with BMP-7 than in patients with non-unions (p < 0.05). Conclusion: Treatment with BMP-7 in patients with former non-unions led to similar cytokine expression patterns after treatment as those found in patients with proper bone healing. Our results suggest that treatment with BMP-7 promote healing of non-unions. Furthermore, quantitative measurement of serum cytokine expression is a promising tool for evaluating the effectiveness of additional non-union therapies such as adjunct application of growth factors