Extremal Graphs for Intersecting Triangles

AbstractIt is known that for a graph on n vertices [n2/4] + 1 edges is sufficient for the existence of many triangles. In this paper, we determine the minimum number of edges sufficient for the existence of k triangles intersecting in exactly one common vertex

Charged particle environment of Titan during the T9 flyby

The ion measurements of the Cassini Plasma Spectrometer are presented which were acquired on 26 December 2005, during the T9 flyby at Titan. The plasma flow and magnetic field directions in the distant plasma environment of the moon were distinctly different from the other flybys. The near-Titan environment, dominated by ions of Titan origin, had a split signature, each with different ion composition; the first region was dominated by dense, slow, and cold ions in the 16-19 and 28-40 amu mass range, the second region contained only ions with mass 1 and 2, much less dense and less slow. Magnetospheric ions penetrate marginally into region 1, whereas the region-2 ion population is mixed. A detailed analysis has led us to conclude that the first event was due to the crossing of the mantle of Titan, whereas the second one very likely was a wake crossing. The split indicates the non-convexity of the ion-dominated volume around Titan. Both ion distributions are analysed in detail

Correlation effects on electronic and optical properties of a C60 molecule: A variational Monte Carlo study

The electronic and optical properties of the neutral C60 molecule are investigated in the extended Su-Schrieffer-Heeger model including a Hubbard-type on-site interaction by the variational Monte Carlo (VMC) method. The optical energy gap Eg of the molecule and the energies of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) have been calculated as functions of the Hubbard interaction strength U divided by the hopping constant t. It is found that the energy of both the HOMO and LUMO levels increase almost equally with increase of U/t, so that the Hubbard term U/t has only a weak effect on Eg for intermediate interaction strengths (U/t<5). This is significantly different from the situation in conducting polymers. Pair-binding energies in the singlet and triplet states have also been calculated by the VMC method for nondimerized molecules, and a comparison has been made with the results obtained by perturbation theory. © 1996 The American Physical Society.published_or_final_versio

Relative efficacy of biological control and cultural management for control of mollusc pests in cool climate vineyards (article)

This is the final version. Available on open access from Taylor & Francis via the DOI in this recordThe dataset associated with this article is located in ORE at: https://doi.org/10.24378/exe.3083Restrictions on the use of synthetic molluscicides highlight the importance of developing alternative control methods. Nevertheless, biocontrol agents can be costlier and less effective than synthetic counterparts. One mean of increasing the efficacy of population suppression is to combine inundative biological control with habitat management to reduce population growth of target pests. Vineyards in the cool, wet climate of western England can suffer from outbreak densities of mollusc pests that damage expanding shoots, developing grapes and promote the transmission of fungal pathogens. In this study we combined the biocontrol agent Nemaslug - Phasmarhabditis hermaphrodita (Schneider) -with a simple habitat management approach (regular mowing) to suppress mollusc pests in vineyards in South Western England. Two sites were treated with NemaSlug and or mowing in a factorial design in early spring coinciding with bud burst and the start of mollusc growth and feeding. Mowing was effective management and resulted in the reduction of slug and snail populations and significantly less damaged vines. Nemaslug did not reduce slug numbers overall but did reduce bud damage, snail numbers and lowered the proportion of sucsceptible Deroceras spp in treated plot. However, effect sizes of nematode biocontrol were small, potentially because this product could not be applied to bare soil. Management practice for cool climate vineyards varies considerably from site to site. This study shows the value of simple habitat management for controlling a novel target and emphasizes how consideration of pest biology can lead to effective alternatives.European Regional Development Fund (ERDF)Cornwall CouncilCouncil for the Isles of Scill

Uncovering hidden flows in physical networks

Chengwei Wang is supported by a studentship funded by the College of Physical Sciences, University of Aberdeen.Peer reviewedPostprintPostprin

Diffusion Processes on Small-World Networks with Distance-Dependent Random-Links

We considered diffusion-driven processes on small-world networks with distance-dependent random links. The study of diffusion on such networks is motivated by transport on randomly folded polymer chains, synchronization problems in task-completion networks, and gradient driven transport on networks. Changing the parameters of the distance-dependence, we found a rich phase diagram, with different transient and recurrent phases in the context of random walks on networks. We performed the calculations in two limiting cases: in the annealed case, where the rearrangement of the random links is fast, and in the quenched case, where the link rearrangement is slow compared to the motion of the random walker or the surface. It has been well-established that in a large class of interacting systems, adding an arbitrarily small density of, possibly long-range, quenched random links to a regular lattice interaction topology, will give rise to mean-field (or annealed) like behavior. In some cases, however, mean-field scaling breaks down, such as in diffusion or in the Edwards-Wilkinson process in "low-dimensional" small-world networks. This break-down can be understood by treating the random links perturbatively, where the mean-field (or annealed) prediction appears as the lowest-order term of a naive perturbation expansion. The asymptotic analytic results are also confirmed numerically by employing exact numerical diagonalization of the network Laplacian. Further, we construct a finite-size scaling framework for the relevant observables, capturing the cross-over behaviors in finite networks. This work provides a detailed account of the self-consistent-perturbative and renormalization approaches briefly introduced in two earlier short reports.Comment: 36 pages, 27 figures. Minor revisions in response to the referee's comments. Furthermore, some typos were fixed and new references were adde

Fluctuation of the download network

The scaling behavior of fluctuation for a download network which we have investigated a few years ago based upon Zhang's Encophysics web page has been presented. A power law scaling, namely $\sigma \sim ^ \alpha$ exists between the dispersion $\sigma$ and average flux $$ of the download rates. The fluctuation exponent $\alpha$ is neither 1/2 nor 1 which was claimed as two universal fluctuation classes in previous publication, instead it varies from 1/2 to 1 with the time window in which the download data were accumulated. The crossover behavior of fluctuation exponents can be qualitatively understood by the external driving fluctuation model for a small-size system or a network traffic model which suggests congestion as the origin.Comment: 4 pages, 4 figure

Strobe sequence design for haplotype assembly

Abstract Background Humans are diploid, carrying two copies of each chromosome, one from each parent. Separating the paternal and maternal chromosomes is an important component of genetic analyses such as determining genetic association, inferring evolutionary scenarios, computing recombination rates, and detecting cis-regulatory events. As the pair of chromosomes are mostly identical to each other, linking together of alleles at heterozygous sites is sufficient to phase, or separate the two chromosomes. In Haplotype Assembly, the linking is done by sequenced fragments that overlap two heterozygous sites. While there has been a lot of research on correcting errors to achieve accurate haplotypes via assembly, relatively little work has been done on designing sequencing experiments to get long haplotypes. Here, we describe the different design parameters that can be adjusted with next generation and upcoming sequencing technologies, and study the impact of design choice on the length of the haplotype. Results We show that a number of parameters influence haplotype length, with the most significant one being the advance length (distance between two fragments of a clone). Given technologies like strobe sequencing that allow for large variations in advance lengths, we design and implement a simulated annealing algorithm to sample a large space of distributions over advance-lengths. Extensive simulations on individual genomic sequences suggest that a non-trivial distribution over advance lengths results a 1-2 order of magnitude improvement in median haplotype length. Conclusions Our results suggest that haplotyping of large, biologically important genomic regions is feasible with current technologies

Lack of significant association of an insertion/deletion polymorphism in the angiotensin converting enzyme (ACE) gene with tropical calcific pancreatitis

BACKGROUND: The genetic basis of tropical calcific pancreatitis (TCP) is different and is explained by mutations in the pancreatic secretory trypsin inhibitor (SPINK1) gene. However, mutated SPINK1 does not account for the disease in all the patients, neither does it explain the phenotypic heterogeneity between TCP and fibro-calculous pancreatic diabetes (FCPD). Recent studies suggest a crucial role for pancreatic renin-angiotensin system during chronic hypoxia in acute pancreatitis and for angiotensin converting enzyme (ACE) inhibitors in reducing pancreatic fibrosis in experimental models. We investigated the association of ACE gene insertion/deletion (I/D) polymorphism in TCP patients using a case-control approach. Since SPINK1 mutations are proposed a modifier role, we also investigated its interaction with the ACE gene variant. METHODS: We analyzed the I/D polymorphism in the ACE gene (g.11417_11704del287) in 171 subjects comprising 91 TCP and 80 FCPD patients and compared the allelic and genotypic frequency in them with 99 healthy ethnically matched control subjects. RESULTS: We found 46% and 21% of TCP patients, 56% and 19.6% of FCPD patients and 54.5% and 19.2% of the healthy controls carrying the I/D and D/D genotypes respectively (P>0.05). No significant difference in the clinical picture was observed between patients with and without the del allele at the ACE in/del polymorphism in both categories. No association was observed with the presence or absence of N34S SPINK1 mutation in these patients. CONCLUSION: We conclude that the ACE insertion/deletion variant does not show any significant association with the pathogenesis, fibrosis and progression of tropical calcific pancreatitis and the fibro-calculous pancreatic diabetes