Site participation in the small community experiment

The Small Community Solar Thermal Experiment, planned to test a small, developmental solar thermal power plant in a small community application, is assessed. The baseline plan is to install a field of parabolic dishes with distributed generation to provide 1 MWe of experimental power. Participation by the site proposer is an integral element of the experiment; the proposer will provide a ten-acre site, a connection to the electrical distributional system serving the small community, and various services. In addition to the primary participant, site study efforts may be pursued at as many as five alternative sites

Non-equilibrium Berezinskii-Kosterlitz-Thouless Transition in a Driven Open Quantum System

The Berezinskii-Kosterlitz-Thouless mechanism, in which a phase transition is mediated by the proliferation of topological defects, governs the critical behaviour of a wide range of equilibrium two-dimensional systems with a continuous symmetry, ranging from superconducting thin films to two-dimensional Bose fluids, such as liquid helium and ultracold atoms. We show here that this phenomenon is not restricted to thermal equilibrium, rather it survives more generally in a dissipative highly non-equilibrium system driven into a steady-state. By considering a light-matter superfluid of polaritons, in the so-called optical parametric oscillator regime, we demonstrate that it indeed undergoes a vortex binding-unbinding phase transition. Yet, the exponent of the power-law decay of the first order correlation function in the (algebraically) ordered phase can exceed the equilibrium upper limit -- a surprising occurrence, which has also been observed in a recent experiment. Thus we demonstrate that the ordered phase is somehow more robust against the quantum fluctuations of driven systems than thermal ones in equilibrium.Comment: 11 pages, 9 figure

Analysis of clusterin expression changes as a biomarker of osteoarthritis

Purpose: The discovery and validation of arthritis-related biomarkers and establishment of methodology for proteomic studies in osteoarthritis (OA) are needed. Proteomics strategies have identified many proteins that may relate to pathological mechanisms of OA, however targeted approaches are required to validate the roles of these proteins. This study aimed to use mass spectrometry and western blotting to identify peptides from several proteins in the secretome of chondrocytes, cartilage explants and osteochondral biopsies treated with inflammatory cytokines over a 2-week period, to evaluate their potential as biomarkers of OA progression. Methods: Healthy cartilage was obtained from fetlock joints of skeletally mature horses, euthanized for unrelated veterinary reasons. Cartilage explants were isolated using a 6 mm biopsy, with discs placed into wells (3 discs per 1 ml DMEM + 1% Pen/Strep) before incubation for 24 hours (37 °C, 5% CO2). After this equilibration period, the media was removed and replaced with either fresh DMEM + 1% Pen/Strep or DMEM supplemented with 1% Pen/Strep containing TNFα and IL-1β both at 10ng/ml. Explants were culture for 7–14 days with the cytokines replaced every 4th day. For cell based assays chondrocytes were isolated from tissue using 70U pronase for 1hr at 37 °C and overnight digestion at 37°C using a 0.2% collagenase II solution. The cell suspension was filtered and washed before being seeded into culture flasks and cultured until confluence was reached (37°C, 5% CO2). Once cultures were established cells were split into two groups: healthy control (DMEM supplemented with 1% Pen/Strep and 10% foetal calf serum) or stimulated cells (DMEM as above plus TNFα and IL-1β both at 10ng/ml). Chondroyctes were cytokine-stimulated for up to one week. Cells were used in experiments up to the 2nd passage. Results: Mass spectrometry data showed that peptides representative of clusterin were found to decrease following 7 days of inflammatory stimulation. Western blotting of secreted proteins in media of cartilage explants or chondrocyte showed that clusterin expression was reduced following 7 days of cytokine treatment. Catabolic matrix metalloproteinase enzymes MMP1, MMP3 and MMP13, as well the matrix component cartilage oligomeric protein (COMP) were all found to have an increased abundance in the media of the cytokine treated samples. This data was supported by qPCR for clusterin gene expression which showed initially mRNA levels increased 3 day after inflammatory stimulation but expression was lost after 7 days. Western blotting of media from the osteochondral biopsies showed an increase in clusterin expression after 7 days of inflammatory stimulation however clusterin protein expression could not be detected after 14 days of treatment, indicating a delayed response compared to cartilage tissue alone. Conclusions: The equine chondrocytes, cartilage explant and osteochondral biopsy models exhibited highest clusterin secretion in untreated cultures. IL-1β and TNFα treatment caused a reduction in clusterin secretion. Clusterin acts as a chaperone to aid protein refolding in situations of stress and is constitutively secreted by mammalian cells. IL-1β and TNFα appear to interrupt clusterin secretion and therefore the protection it may offer healthy functioning cells. Previous studies have reported variable data, with some studies indicating a decrease in clusterin in OA, while others indicate an increase in clusterin expression. Our results suggest the clusterin increases immediately after inflammatory stimulation but is lost after prolonged exposure. Therefore, levels of secreted clusterin may be a candidate biomarker for OA progression

Expanding the expressive power of Monadic Second-Order logic on restricted graph classes

We combine integer linear programming and recent advances in Monadic Second-Order model checking to obtain two new algorithmic meta-theorems for graphs of bounded vertex-cover. The first shows that cardMSO1, an extension of the well-known Monadic Second-Order logic by the addition of cardinality constraints, can be solved in FPT time parameterized by vertex cover. The second meta-theorem shows that the MSO partitioning problems introduced by Rao can also be solved in FPT time with the same parameter. The significance of our contribution stems from the fact that these formalisms can describe problems which are W[1]-hard and even NP-hard on graphs of bounded tree-width. Additionally, our algorithms have only an elementary dependence on the parameter and formula. We also show that both results are easily extended from vertex cover to neighborhood diversity.Comment: Accepted for IWOCA 201

Claw-free t-perfect graphs can be recognised in polynomial time

A graph is called t-perfect if its stable set polytope is defined by non-negativity, edge and odd-cycle inequalities. We show that it can be decided in polynomial time whether a given claw-free graph is t-perfect

On Structural Parameterizations of Hitting Set: Hitting Paths in Graphs Using 2-SAT

Hitting Set is a classic problem in combinatorial optimization. Its input consists of a set system F over a finite universe U and an integer t; the question is whether there is a set of t elements that intersects every set in F. The Hitting Set problem parameterized by the size of the solution is a well-known W[2]-complete problem in parameterized complexity theory. In this paper we investigate the complexity of Hitting Set under various structural parameterizations of the input. Our starting point is the folklore result that Hitting Set is polynomial-time solvable if there is a tree T on vertex set U such that the sets in F induce connected subtrees of T. We consider the case that there is a treelike graph with vertex set U such that the sets in F induce connected subgraphs; the parameter of the problem is a measure of how treelike the graph is. Our main positive result is an algorithm that, given a graph G with cyclomatic number k, a collection P of simple paths in G, and an integer t, determines in time 2^{5k} (|G| +|P|)^O(1) whether there is a vertex set of size t that hits all paths in P. It is based on a connection to the 2-SAT problem in multiple valued logic. For other parameterizations we derive W[1]-hardness and para-NP-completeness results.Comment: Presented at the 41st International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2015. (The statement of Lemma 4 was corrected in this update.

Vortex and half-vortex dynamics in a spinor quantum fluid of interacting polaritons

Spinorial or multi-component Bose-Einstein condensates may sustain fractional quanta of circulation, vorticant topological excitations with half integer windings of phase and polarization. Matter-light quantum fluids, such as microcavity polaritons, represent a unique test bed for realising strongly interacting and out-of-equilibrium condensates. The direct access to the phase of their wavefunction enables us to pursue the quest of whether half vortices ---rather than full integer vortices--- are the fundamental topological excitations of a spinor polariton fluid. Here, we are able to directly generate by resonant pulsed excitations, a polariton fluid carrying either the half or full vortex states as initial condition, and to follow their coherent evolution using ultrafast holography. Surprisingly we observe a rich phenomenology that shows a stable evolution of a phase singularity in a single component as well as in the full vortex state, spiraling, splitting and branching of the initial cores under different regimes and the proliferation of many vortex anti-vortex pairs in self generated circular ripples. This allows us to devise the interplay of nonlinearity and sample disorder in shaping the fluid and driving the phase singularities dynamicsComment: New version complete with revised modelization, discussion and added material. 8 pages, 7 figures. Supplementary videos: https://drive.google.com/folderview?id=0B0QCllnLqdyBfmc2ai0yVF9fa2g2VnZodGUwemVkLThBb3BoOVRKRDJMS2dUdjlZdkRTQk

The Parameterized Complexity of Domination-type Problems and Application to Linear Codes

We study the parameterized complexity of domination-type problems. (sigma,rho)-domination is a general and unifying framework introduced by Telle: a set D of vertices of a graph G is (sigma,rho)-dominating if for any v in D, |N(v)\cap D| in sigma and for any $v\notin D, |N(v)\cap D| in rho. We mainly show that for any sigma and rho the problem of (sigma,rho)-domination is W[2] when parameterized by the size of the dominating set. This general statement is optimal in the sense that several particular instances of (sigma,rho)-domination are W[2]-complete (e.g. Dominating Set). We also prove that (sigma,rho)-domination is W[2] for the dual parameterization, i.e. when parameterized by the size of the dominated set. We extend this result to a class of domination-type problems which do not fall into the (sigma,rho)-domination framework, including Connected Dominating Set. We also consider problems of coding theory which are related to domination-type problems with parity constraints. In particular, we prove that the problem of the minimal distance of a linear code over Fq is W[2] for both standard and dual parameterizations, and W[1]-hard for the dual parameterization. To prove W[2]-membership of the domination-type problems we extend the Turing-way to parameterized complexity by introducing a new kind of non deterministic Turing machine with the ability to perform `blind' transitions, i.e. transitions which do not depend on the content of the tapes. We prove that the corresponding problem Short Blind Multi-Tape Non-Deterministic Turing Machine is W[2]-complete. We believe that this new machine can be used to prove W[2]-membership of other problems, not necessarily related to dominationComment: 19 pages, 2 figure

The Claims Culture: A Taxonomy of Industry Attitudes

This paper presents an analysis of a familiar aspect of construction industry culture that we have dubbed 'the claims culture'. This is a culture of contract administration that lays a strong emphasis on the planning and management of claims. The principal elements of the analysis are two sets of distinctions. The first comprises economic and occupational orders, referring to two kinds of control that are exercised over the construction process; predicated respectively on economic ownership and occupational competence. The second refers to contrasting attitudes towards relationships and problem solving within these orders: respectively 'distributive' and 'integrative'. The concepts of economic and occupational order entail further sub-categories. The various attitudes associated with these categories and sub-categories are described. They are assessed as to their consequences for change initiatives in the industry