Equilibration through local information exchange in networks

We study the equilibrium states of energy functions involving a large set of real variables, defined on the links of sparsely connected networks, and interacting at the network nodes, using the cavity and replica methods. When applied to the representative problem of network resource allocation, an efficient distributed algorithm is devised, with simulations showing full agreement with theory. Scaling properties with the network connectivity and the resource availability are found.Comment: v1: 7 pages, 1 figure, v2: 4 pages, 2 figures, simplified analysis and more organized results, v3: minor change

Pancreatectomy for metastatic real cell carcinoma : twenty years of experience at a tertiary centre

Renal Cell Carcinoma (RCC) accounts for approximately 90% of primary renal malignancies, of which the clear cell subtype is most common. While metastatic disease is common at the time of diagnosis and generally confers a poor prognosis, metastatic RCC may demonstrate relatively indolent behaviour and present many years after resection of the primary tumour, including to the pancreas. The available literature suggested that surgical resection was appropriate for select patients, including those with a solitary pancreatic metastasis, minimal comorbidities and uncomplicated progress from initial treatment of their primary renal malignancy. A retrospective case series of patients presenting with RCC metastases to the pancreas, managed via surgical resection at a tertiary teaching hospital was reviewed. Analysis of patient demographics, investigations, management and outcomes were performed, with a focus on post-operative morbidity and overall survival. Between 2000 and 2020, 7 patients underwent pancreatic resection of RCC metastases at our tertiary teaching hospital with curative intent. Median age at time of resection was 66 years. No post-operative mortality or major morbidity was experienced by the 7 patients, although 4 patients developed some degree of pancreatic insufficiency. Four patients experienced recurrent metastatic RCC, with median time to recurrence of 3.5 years. This was the largest local study to describe an Australian experience of the surgical management of RCC pancreatic metastases. These patients are frequently afforded prolonged survival following pancreatic resection, but often develop other distant sites of disease and second renal tumours

Optimal Location of Sources in Transportation Networks

We consider the problem of optimizing the locations of source nodes in transportation networks. A reduction of the fraction of surplus nodes induces a glassy transition. In contrast to most constraint satisfaction problems involving discrete variables, our problem involves continuous variables which lead to cavity fields in the form of functions. The one-step replica symmetry breaking (1RSB) solution involves solving a stable distribution of functionals, which is in general infeasible. In this paper, we obtain small closed sets of functional cavity fields and demonstrate how functional recursions are converted to simple recursions of probabilities, which make the 1RSB solution feasible. The physical results in the replica symmetric (RS) and the 1RSB frameworks are thus derived and the stability of the RS and 1RSB solutions are examined.Comment: 38 pages, 18 figure

Finite-Connectivity Spin-Glass Phase Diagrams and Low Density Parity Check Codes

We obtain phase diagrams of regular and irregular finite connectivity spin-glasses. Contact is firstly established between properties of the phase diagram and the performances of low density parity check codes (LDPC) within the Replica Symmetric (RS) ansatz. We then study the location of the dynamical and critical transition of these systems within the one step Replica Symmetry Breaking theory (RSB), extending similar calculations that have been performed in the past for the Bethe spin-glass problem. We observe that, away from the Nishimori line, in the low temperature region, the location of the dynamical transition line does change within the RSB theory, in comparison with the (RS) case. For LDPC decoding over the binary erasure channel we find, at zero temperature and rate R=1/4 an RS critical transition point located at p_c = 0.67 while the critical RSB transition point is located at p_c = 0.7450, to be compared with the corresponding Shannon bound 1-R. For the binary symmetric channel (BSC) we show that the low temperature reentrant behavior of the dynamical transition line, observed within the RS ansatz, changes within the RSB theory; the location of the dynamical transition point occurring at higher values of the channel noise. Possible practical implications to improve the performances of the state-of-the-art error correcting codes are discussed.Comment: 21 pages, 15 figure

Dynamic Status Signal Reflects Outcome of Social Interactions, but Not Energetic Stress

Social defeat induces stress-responses in a wide array of vertebrates and can generate winner-loser effects. Dynamic condition-dependent signaling systems that reflect preparation for subsequent agonistic interactions, and thereby mediate winner-loser effects, should be more sensitive to competitive history than to non-social sources of stress. Bill color of female American goldfinches (Spinus tristus) is a dynamic condition-dependent ornament that functions as a signal of competitive status and mediates intrasexual agonistic social interactions. We tested the “social experience signaling hypothesis” in female goldfinches by (1) manipulating a non-social energetic stressor by experimentally elevating flight costs via wing-clipping in free-ranging birds, and (2) manipulating social experience by staging competitive interactions among captive birds. Bill color change did not differ between wing clipped and non-clipped females, even though stress-response, as measured by the heterophil to lymphocyte (H:L) ratio, increased significantly in clipped females relative to unclipped females. In contrast, winners and losers in the social experience experiment differed significantly in the degree and direction of bill color change following social contests, with bill color increasing in winners and decreasing in losers. These results suggest that dynamic bill color of female American goldfinches signals recent social history, but is less sensitive to some stressors stemming from non-social sources, and thereby suggest that signals can evolve sensitivity to specific types of processes relevant to the context in which they are used

Reflecting photonics: reaching new audiences through new partnerships – IYL 2015 and the Royal Horticultural Society Flower Show

The ‘Reflecting Photonics’ show garden was exhibited at the 2015 Royal Horticultural Society (RHS) Flower Show in Tatton Park, UK, to celebrate the International Year of Light and Light-based Technologies. Elks-Smith Garden Design alongside landscapers ‘Turf N’ Earth’ collaborated with researchers, marketing and outreach professionals from the University of Southampton to design, construct and exhibit a photonics-themed garden. The garden and supporting exhibition united science and art to reach new audiences – particularly family groups alongside other key influencers to the young – and showcased the world-leading research in optical fibers at the university in an accessible manner. Researchers and a publicity professional, funded by the EPSRC Centre for Innovative Manufacturing in Photonics, developed an integrated approach to the event’s public engagement and marketing. The overarching aim was to influence a positive change in the attitude of the garden visitors towards physics and photonics, with additional focus on promoting careers for women in STEM. The show garden won an RHS Gold Medal award and the coveted ‘People’s Choice Award’ for the best large garden. The project subsequently won the South East England Physics Network Public Engagement Innovation Project Award. Approximately 80,000 visitors saw the garden, with a further three million television viewers on a popular British gardening show. There were also over 75,400 Tweet impressions on social media. This paper discusses the project aims, explores the design of the garden and its relationship with the research, describes the work of the public engagement team, and outlines the impact of the event

Palette-colouring: a belief-propagation approach

We consider a variation of the prototype combinatorial-optimisation problem known as graph-colouring. Our optimisation goal is to colour the vertices of a graph with a fixed number of colours, in a way to maximise the number of different colours present in the set of nearest neighbours of each given vertex. This problem, which we pictorially call "palette-colouring", has been recently addressed as a basic example of problem arising in the context of distributed data storage. Even though it has not been proved to be NP complete, random search algorithms find the problem hard to solve. Heuristics based on a naive belief propagation algorithm are observed to work quite well in certain conditions. In this paper, we build upon the mentioned result, working out the correct belief propagation algorithm, which needs to take into account the many-body nature of the constraints present in this problem. This method improves the naive belief propagation approach, at the cost of increased computational effort. We also investigate the emergence of a satisfiable to unsatisfiable "phase transition" as a function of the vertex mean degree, for different ensembles of sparse random graphs in the large size ("thermodynamic") limit.Comment: 22 pages, 7 figure

Tractable Inference for Probabilistic Data Models

Based on ideas from statistical physics, we present an approximation technique for probabilistic data models with a large number of hidden variables. We give examples for two non–trivial applications.

The Statistical Physics of Regular Low-Density Parity-Check Error-Correcting Codes

A variation of Gallager error-correcting codes is investigated using statistical mechanics. In codes of this type, a given message is encoded into a codeword which comprises Boolean sums of message bits selected by two randomly constructed sparse matrices. The similarity of these codes to Ising spin systems with random interaction makes it possible to assess their typical performance by analytical methods developed in the study of disordered systems. The typical case solutions obtained via the replica method are consistent with those obtained in simulations using belief propagation (BP) decoding. We discuss the practical implications of the results obtained and suggest a computationally efficient construction for one of the more practical configurations.Comment: 35 pages, 4 figure