Nonlinear conductance of nanowires - A signature of Luttinger liquid effects?

We analyze recent measurements of the room temperature current-voltage characteristics of gold nanowires, whose zero current conductance is quantized in units of $2e^2/h$. A faster than linear increase of current with voltage was observed at low voltages beginning from $V_c=0.1$V. We analyze the nonlinear behavior in terms of a dynamic Coulomb blockade of conducting modes and show that it may be explained as a Luttinger-liquid effect.Comment: 13 pages, latex with supplied stylefile, 3 figures in eps format, submitted to Superlattices and Microstructure

Asymptotically-Optimal Topological Nearest-Neighbor Filtering

Nearest-neighbor finding is a major bottleneck for sampling-based motion planning algorithms. The cost of finding nearest neighbors grows with the size of the roadmap, leading to a significant computational bottleneck for problems which require many configurations to find a solution. In this work, we develop a method of mapping configurations of a jointed robot to neighborhoods in the workspace that supports fast search for configurations in nearby neighborhoods. This expedites nearest-neighbor search by locating a small set of the most likely candidates for connecting to the query with a local plan. We show that this filtering technique can preserve asymptotically-optimal guarantees with modest requirements on the distance metric. We demonstrate the method’s efficacy in planning problems for rigid bodies and both fixed and mobile-base manipulators

Palaeobiology, ecology, and distribution of stromatoporoid faunas in biostromes of the mid-Ludlow of Gotland

Six well exposed mid−Ludlow stromatoporoid−dominated reef biostromes in four localities from the Hemse Group in southeastern Gotland, Sweden comprise a stromatoporoid assemblage dominated by four species; Clathrodictyon mohicanum, “Stromatopora” bekkeri, Plectostroma scaniense, and Lophiostroma schmidtii. All biostromes investigated in this area (of approximately 30 km2) are interpreted to belong to a single faunal assemblage forming a dense accumulation of fossils that is probably the best exposed stromatoporoid−rich deposit of the Silurian. The results from this comprehensive study strengthen earlier interpretations of a combination of genetic and environmental control on growth−forms of the stromatoporoids. Growth styles are similar for stromatoporoids in all six biostromes. Differences in biostrome fabric are due to variations in the degree of disturbance by storms. The uniformity of facies and the widespread low−diversity fauna support the view that palaeoenvironmental conditions were similar across the area where these biostromes crop out, and promoted the extraordinary growth of stromatoporoids in this shallow shelf area

Topology-Guided Roadmap Construction With Dynamic Region Sampling

Many types of planning problems require discovery of multiple pathways through the environment, such as multi-robot coordination or protein ligand binding. The Probabilistic Roadmap (PRM) algorithm is a powerful tool for this case, but often cannot efficiently connect the roadmap in the presence of narrow passages. In this letter, we present a guidance mechanism that encourages the rapid construction of well-connected roadmaps with PRM methods. We leverage a topological skeleton of the workspace to track the algorithm\u27s progress in both covering and connecting distinct neighborhoods, and employ this information to focus computation on the uncovered and unconnected regions. We demonstrate how this guidance improves PRM\u27s efficiency in building a roadmap that can answer multiple queries in both robotics and protein ligand binding applications

Influence of long time ageing on ductility and toughness in the stainless steel 310 in the presence of banded microstructure

During service at elevated temperatures extensive formation of particles can take place that can have adramatic influence on mechanical properties. Precipitation of ?-phase and M23C6-carbides have been studiedboth experimentally and with thermodynamic modelling for 25Cr20Ni austenitic stainless steels (AISI 310) at800 ºC for up to 5000 h. Previous work has demonstrated that the modelling could describe the nucleation andgrowth satisfactory. After long term ageing the particles form bands in the microstructure. In the present paperthe influence of these bands on ductility and toughness at room temperature is analysed. For this purposepreviously developed models for ductility and toughness are utilised. Model values for banded and non-bandedmicrostructures have been generated for casts of 310 in fine and coarse grained conditions with 0.04 and0.12%N. The model values show that in the coarse grained condition, no reduction in ductility and toughnesscan be expected in the banded microstructure. In the fine grained condition a modest reduction is predicted

Evaluating the outcomes of collaborative wildlife governance: The role of social-ecological system context and collaboration dynamics

The acknowledgement of uncertainty and complexity in social-ecological systems has increased the implementation of collaborative governance regimes for environmental issues. The performance of these new regimes to deliver favourable social and ecological outcomes must therefore be evaluated. We focus on the case of Swedish wildlife governance, which has a tradition of using collaborative elements. In relation to moose (Alces alces), these collaborative aspects were recently formalized in an amended policy. We aim to assess some aspects of this new regime's performance with respect to intermediate ecological outcomes (i.e. quota fulfilment). We use path analysis to test the causal effects of system context and collaboration dynamics on governance outcomes. Collaboration dynamics were assessed using a web-based survey sent to all stakeholders in Moose Management Groups (response rate = 82 %). Our originally specified model yielded a good fit (SRMR of .030 and robust TLI of .996) and explained 20 % of the variation in outcomes. Context variables revealed significant direct effects on collaboration dynamics and outcomes. Larger Moose Management Areas and fluctuations in forage availability required more time investment from actors, while high land use diversity and density of other ungulate species negatively affected moose quota fulfilment. Moose Management Groups that invested more time and perceived to have a good knowledge base achieved better quota fulfilment. Collaboration dynamics thus had a positive direct effect on outcomes. From a policy perspective, our results raise questions regarding institutional fit because context factors had significant negative effects on collaboration dynamics and the outcomes of the collaborative process

Effect of Charge Fluctuations on the Persistent Current through a Quantum Dot

We study coherent charge transfer between an Aharonov-Bohm ring and a side-attached quantum dot. The charge fluctuation between the two sub-structures is shown to give rise to algebraic suppression of the persistent current circulating the ring as the size of the ring becomes relatively large. The charge fluctuation at resonance provides transition between the diamagnetic and the paramagnetic states. Universal scaling, crossover behavior of the persistent current from a continuous to a discrete energy limit in the ring is also discussed.Comment: 5 pages, 4 figure

A remark on the expressivity of asynchronous TeamLTL and HyperLTL

Linear temporal logic (LTL) is used in system verification to write formal specifications for reactive systems. However, some relevant properties, e.g. non-inference in information flow security, cannot be expressed in LTL. A class of such properties that has recently received ample attention is known as hyperproperties. There are two major streams in the research regarding capturing hyperproperties, namely hyperlogics, which extend LTL with trace quantifiers (HyperLTL), and logics that employ team semantics, extending truth to sets of traces. In this article we explore the relation between asynchronous LTL under set-based team semantics (TeamLTL) and HyperLTL. In particular we consider the extensions of TeamLTL with the Boolean disjunction and a fragment of the extension of TeamLTL with the Boolean negation, where the negation cannot occur in the left-hand side of the Until-operator or within the Global-operator. We show that TeamLTL extended with the Boolean disjunction is equi-expressive with the positive Boolean closure of HyperLTL restricted to one universal quantifier, while the left-downward closed fragment of TeamLTL extended with the Boolean negation is expressively equivalent with the Boolean closure of HyperLTL restricted to one universal quantifier