Relativistic Ring-Diagram Nuclear Matter Calculations

A relativistic extension of the particle-particle hole-hole ring-diagram many-body formalism is developed by using the Dirac equation for single-particle motion in the medium. Applying this new formalism, calculations are performed for nuclear matter. The results show that the saturation density is improved and the equation of state becomes softer as compared to corresponding Dirac-Brueckner-Hartree-Fock calculations. Using the Bonn A potential, nuclear matter is predicted to saturate at an energy per nucleon of --15.30 MeV and a density equivalent to a Fermi momentum of 1.38 fm$^{-1}$, in excellent agreement with empirical information. The compression modulus is 152 MeV at the saturation point.Comment: 23 pages text (LaTex) and 2 figures (paper, will be faxed upon request), UI-NTH-92-0

Testing the performance of environmental DNA metabarcoding for surveying highly diverse tropical fish communities: A case study from Lake Tanganyika

Background and Aims Environmental DNA (eDNA) metabarcoding provides a highly sensitive method of surveying freshwater fish communities, although studies to date have largely been restricted to temperate ecosystems. Due to limited reference sequence availability and challenges identifying closely related and rare species in diverse tropical ecosystems, the effectiveness of metabarcoding methods for surveying tropical fish communities from eDNA samples remains uncertain. To address this, we applied an eDNA metabarcoding approach to survey Lake Tanganyika's (LT) species‐rich littoral fish communities. Materials and Methods As this system contains many closely related species, particularly cichlid fishes, we used four primer sets including a cichlid‐specific primer set (Cichlid_CR). A reference database was built for the 12s, 16s, and control region for 358 fish species including over 93% of known cichlids. Results and Discussion In silico and in situ results demonstrated wide variability in the taxonomic resolution of assignments by each primer with the cichlid‐specific marker (Cichlid_CR) enabling greater species‐level assignments for this highly diverse family. A greater number of non‐cichlid teleost species were detected at sites compared to the visual survey data. For cichlid species however, sequencing depth substantially influenced species richness estimates obtained from eDNA samples, with increased depths producing estimates comparable to that obtained from the visual survey data. Conclusions Our study highlights the importance of sequencing depth and local reference databases when undertaking metabarcoding studies within diverse ecosystems, as well as demonstrating the potential of eDNA metabarcoding for surveying diverse tropical fish communities, even those containing closely related species within evolutionary radiations

Dirac Hartree-Fock for Finite Nuclei Employing realistic Forces

We discuss two different approximation schemes for the self-consistent solution of the {\it relativistic} Brueckner-Hartree-Fock equation for finite nuclei. In the first scheme, the Dirac effects are deduced from corresponding nuclear matter calculations, whereas in the second approach the local-density approximation is used to account for the effects of correlations. The results obtained by the two methods are very similar. Employing a realistic one-boson-exchange potential (Bonn~A), the predictions for energies and radii of $^{16}$O and $^{40}$Ca come out in substantially better agreement with experiment as compared to non-relativistic approaches. As a by-product of our study, it turns out that the Fock exchange-terms, ignored in a previous investigation, are not negligible.Comment:

Network Cournot Competition

Cournot competition is a fundamental economic model that represents firms competing in a single market of a homogeneous good. Each firm tries to maximize its utility---a function of the production cost as well as market price of the product---by deciding on the amount of production. In today's dynamic and diverse economy, many firms often compete in more than one market simultaneously, i.e., each market might be shared among a subset of these firms. In this situation, a bipartite graph models the access restriction where firms are on one side, markets are on the other side, and edges demonstrate whether a firm has access to a market or not. We call this game \emph{Network Cournot Competition} (NCC). In this paper, we propose algorithms for finding pure Nash equilibria of NCC games in different situations. First, we carefully design a potential function for NCC, when the price functions for markets are linear functions of the production in that market. However, for nonlinear price functions, this approach is not feasible. We model the problem as a nonlinear complementarity problem in this case, and design a polynomial-time algorithm that finds an equilibrium of the game for strongly convex cost functions and strongly monotone revenue functions. We also explore the class of price functions that ensures strong monotonicity of the revenue function, and show it consists of a broad class of functions. Moreover, we discuss the uniqueness of equilibria in both of these cases which means our algorithms find the unique equilibria of the games. Last but not least, when the cost of production in one market is independent from the cost of production in other markets for all firms, the problem can be separated into several independent classical \emph{Cournot Oligopoly} problems. We give the first combinatorial algorithm for this widely studied problem

Variance based weighting of multisensory head rotation signals for verticality perception

We tested the hypothesis that the brain uses a variance-based weighting of multisensory cues to estimate head rotation to perceive which way is up. The hypothesis predicts that the known bias in perceived vertical, which occurs when the visual environment is rotated in a vertical-plane, will be reduced by the addition of visual noise. Ten healthy participants sat head-fixed in front of a vertical screen presenting an annulus filled with coloured dots, which could rotate clockwise or counter-clockwise at six angular velocities (1, 2, 4, 6, 8, 16°/s) and with six levels of noise (0, 25, 50, 60, 75, 80%). Participants were required to keep a central bar vertical by rotating a hand-held dial. Continuous adjustments of the bar were required to counteract low-amplitude low-frequency noise that was added to the bar's angular position. During visual rotation, the bias in verticality perception increased over time to reach an asymptotic value. Increases in visual rotation velocity significantly increased this bias, while the addition of visual noise significantly reduced it, but did not affect perception of visual rotation velocity. The biasing phenomena were reproduced by a model that uses a multisensory variance-weighted estimate of head rotation velocity combined with a gravito-inertial acceleration signal (GIA) from the vestibular otoliths. The time-dependent asymptotic behaviour depends on internal feedback loops that act to pull the brain's estimate of gravity direction towards the GIA signal. The model's prediction of our experimental data furthers our understanding of the neural processes underlying human verticality perception

Visible-light photoredox catalysis enables the biomimetic synthesis of nyingchinoids A, B, and D, and rasumatranin D

German editionThe total synthesis of nyingchinoids A and B has been achieved through successive rearrangements of a 1,2-dioxane intermediate that was assembled using a visible-light photoredox-catalysed aerobic [2+2+2] cycloaddition. Nyingchinoid D was synthesised with a competing [2+2] cycloaddition. Based on NMR data and biosynthetic speculation, we proposed a structure revision of the related natural product rasumatranin D, which was confirmed through total synthesis. Under photoredox conditions, we observed the conversion of a cyclobutane into a 1,2-dioxane through retro-[2+2] cycloaddition followed by aerobic [2+2+2] cycloaddition.Jacob D. Hart, Laura Burchill, Aaron J. Day, Christopher G. Newton, Christopher J. Sumby, David M. Huang, and Jonathan H. Georg

Serum Neu5Gc biomarkers are elevated in primary cutaneous melanoma

Cutaneous melanoma is one of the most aggressive and deadly types of skin cancer and rates of disease are continuing to increase worldwide. Currently, no serum biomarkers exist for the early detection of cutaneous melanoma. Normal human cells cannot make the sialic acid sugar, Neu5Gc, yet human tumor cells express Neu5Gc and Neu5Gc-containing glycoconjugates have been proposed as tumor biomarkers. We engineered a Neu5Gc-specific lectin based on the pentameric B-subunit of the Shiga toxigenic Escherichia coli subtilase cytotoxin, termed SubB2M. We have detected elevated Neu5Gc-containing biomarkers in the sera of ovarian and breast cancer patients in a highly sensitive surface plasmon resonance (SPR)-based assay using our SubB2M lectin. Here, we used the SubB2M-SPR assay to investigate Neu5Gc-containing glycoconjugates in the serum of cutaneous melanoma patients. We found elevated total serum Neu5Gc levels in primary (n ¼ 24) and metastatic (n ¼ 38) patients compared to cancer-free controls (n ¼ 34). Serum Neu5Gc levels detected with SubB2M can distinguish cutaneous melanoma patients from cancer-free controls with high sensitivity and specificity as determined by ROC curve analysis. These data indicate that serum Neu5Gc-containing glycoconjugates are a novel class of biomarkers for cutaneous melanoma, particularly for primary melanoma, and have the potential to contribute to the early diagnosis of this disease.Lucy K. Shewell, Christopher J. Day, Tiana Hippolite, Xavier De Bisscop, James C. Paton, Adrienne W. Paton, Michael P. Jenning

Change in the distribution of a member of the strand line community: the seaweed fly (Diptera: Coelopidae)

1. Coastal organisms are predicted to be particularly susceptible to the impact of global warming. In this study the distribution and relative abundance of two coastal invertebrates, Coelopa frigida (Fabricius) and C. pilipes are investigated. 2. Coelopa pilipes has a more southerly distribution than C. frigida , and prefers a warmer climate. Coelopa pilipes is less resistant to sub-zero temperatures than C. frigida and its northerly distribution is probably limited by cold winter days. 3. The most recent distribution map of C. frigida and C. pilipes in northern Europe was published a decade ago and showed the northerly extent of the distribution of C. pilipes reaching the north coast of mainland Scotland but its complete absence from the Western and Northern Isles. 4. C. pilipes has now spread throughout the Western Isles and the Orkney Islands but is still absent from Shetland. There has also been an increase in the relative frequency of C. pilipes at sites harbouring coelopids on the British mainland. A similar pattern of distribution change along the west coast of Sweden is reported. 5. It is proposed that these changes have occurred primarily as a result of global warming and in particular due to the recent increase in winter temperatures. A number of other indirect effects may have also contributed to these changes, including a probable change in macroalgae distribution. The implications of these changes for the wrack bed ecosystem and at higher trophic levels are considered

Fat mass and obesity associated (FTO) gene influences skeletal muscle phenotypes in non-resistance trained males and elite rugby playing position

Background FTO gene variants have been associated with obesity phenotypes in sedentary and obese populations, but rarely with skeletal muscle and elite athlete phenotypes. Methods In 1089 participants, comprising 530 elite rugby athletes and 559 non-athletes, DNA was collected and genotyped for the FTO rs9939609 variant using real-time PCR. In a subgroup of non-resistance trained individuals (NT; n = 120), we also assessed structural and functional skeletal muscle phenotypes using dual energy x-ray absorptiometry, ultrasound and isokinetic dynamometry. In a subgroup of rugby athletes (n = 77), we assessed muscle power during a countermovement jump. Results In NT, TT genotype and T allele carriers had greater total body (4.8% and 4.1%) and total appendicular lean mass (LM; 3.0% and 2.1%) compared to AA genotype, with greater arm LM (0.8%) in T allele carriers and leg LM (2.1%) for TT, compared to AA genotype. Furthermore, the T allele was more common (94%) in selected elite rugby union athletes (back three and centre players) who are most reliant on LM rather than total body mass for success, compared to other rugby athletes (82%; P = 0.01, OR = 3.34) and controls (84%; P = 0.03, OR = 2.88). Accordingly, these athletes had greater peak power relative to body mass than other rugby athletes (14%; P = 2 x 10-6). Conclusion Collectively, these results suggest that the T allele is associated with increased LM and elite athletic success. This has implications for athletic populations, as well as conditions characterised by low LM such as sarcopenia and cachexia

Computational Nuclear Physics and Post Hartree-Fock Methods

We present a computational approach to infinite nuclear matter employing Hartree-Fock theory, many-body perturbation theory and coupled cluster theory. These lectures are closely linked with those of chapters 9, 10 and 11 and serve as input for the correlation functions employed in Monte Carlo calculations in chapter 9, the in-medium similarity renormalization group theory of dense fermionic systems of chapter 10 and the Green's function approach in chapter 11. We provide extensive code examples and benchmark calculations, allowing thereby an eventual reader to start writing her/his own codes. We start with an object-oriented serial code and end with discussions on strategies for porting the code to present and planned high-performance computing facilities.Comment: 82 pages, to appear in Lecture Notes in Physics (Springer), "An advanced course in computational nuclear physics: Bridging the scales from quarks to neutron stars", M. Hjorth-Jensen, M. P. Lombardo, U. van Kolck, Editor