Comparing variants of strategic ability: how uncertainty and memory influence general properties of games

Alternating-time temporal logic (ATL) is a modal logic that allows to reason about agents’ abilities in game-like scenarios. Semantic variants of ATL are usually built upon different assumptions about the kind of game that is played, including capabilities of agents (perfect vs. imperfect information, perfect vs. imperfect memory, etc.). ATL has been studied extensively in previous years; however, most of the research focused on model checking. Studies of other decision problems (e.g., satisfiability) and formal meta-properties of the logic (like axiomatization or expressivity) have been relatively scarce, and mostly limited to the basic variant of ATL where agents possess perfect information and perfect memory. In particular, a comparison between different semantic variants of the logic is largely left untouched. In this paper, we show that different semantics of ability in ATL give rise to different validity sets. The issue is important for several reasons. First, many logicians identify a logic with its set of true sentences. As a consequence, we prove that different notions of ability induce different strategic logics. Secondly, we show that different concepts of ability induce different general properties of games. Thirdly, the study can be seen as the first systematic step towards satisfiability-checking algorithms for ATL with imperfect information. We introduce sophisticated unfoldings of models and prove invariance results that are an important technical contribution to formal analysis of strategic logics.     

A case study of factor influencing role improvisation in crisis response teams

Common characteristics of crisis situations are ambiguous and unplanned for events. The need for improvised roles can therefore be an imperative factor for the success of an operation. The aim of this study is to deepen the understanding of the processes taking place during improvised work “as it happens”. A case study of a crisis management team at work is presented and provides an in-depth analysis of the information and communication flow of persons acting in improvised roles, including contextual factors influencing the task at hand. The analysis suggests that three main factors lay behind decreased performance by the team when some of its members were forced to take on roles for which they lacked professional training; lack of language skills, lack of domain knowledge and insufficient organizational structure of the tasks. Based on the observations from this case study, we suggest three ways of improving a team’s performance and hence resilience when forced to improvise due to lack of personnel in one or more required competence areas. These are training to take on the responsibility for tasks or roles outside ones professional area of specialization, developing formal routines for changes in roles and tasks and developing and using tools and routines for information sharing.     

Two computational regimes of a single-compartment neuron separated by a planar boundary in conductance space

Recent in vitro data show that neurons respond to input variance with varying sensitivities. Here we demonstrate that Hodgkin-Huxley (HH) neurons can operate in two computational regimes: one that is more sensitive to input variance (differentiating) and one that is less sensitive (integrating). A boundary plane in the 3D conductance space separates these two regimes. For a reduced HH model, this plane can be derived analytically from the V nullcline, thus suggesting a means of relating biophysical parameters to neural computation by analyzing the neuron's dynamical system.     

A combined dislocation—cohesive zone model for fracture in a confined ductile layer

The collective dislocation behavior near a crack tip in a ductile layer sandwiched between two brittle solids is analyzed via two-dimensional dislocation dynamics (DD) simulations that incorporate a cohesive zone (CZ) model. The cohesive crack tip is treated as part of a much larger finite crack confined in the ductile layer. The underlying boundary value problem is formulated with a set of boundary integral equations and numerically evaluated with a collocation method. The fracture energy of the layered composite material is shown to be strongly correlated with the layer thickness and is directly influenced by the cohesive strength of the ductile layer (Hsia KJ et al. (1994) J Mech Phys Solids 6 877–896).     

Polycrystalline silicon films on glass grown by amorphous-liquid-crystalline transition at temperatures below 330 °C

An approach to deposit polycrystalline silicon layers on amorphous substrates is presented. It is shown that metastable amorphous silicon can be transformed into its more stable microcrystalline structure at a temperature below 330 °C via an intermediate liquid solution stage. In particular, the interaction of liquid indium nanodroplets in contact with amorphous silicon is shown to lead to the formation of circular polycrystalline domains. Crystallinity of these domains is analyzed by micro-Raman spectroscopy. The droplet size necessary for the onset of crystallization is related to the temperature of the film. Full coverage of the substrate with microcrystalline silicon has been obtained at 320 °C within less than one hour. These films might act as seeding layers for further enlargement by steady-state liquid phase epitaxy.     

CVD-based tungsten carbide schottky contacts to 6H-SiC for very high-temperature operation

In this study, tungsten carbide, with its hardness, chemical inertness, thermal stability and low resistivity (25 μΩ cm)¹ is shown as a reliable contact material to n- and p-type 6H-SiC for very high temperature applications. WC films with thicknesses of 100–150 nm were deposited by chemical vapor deposition (CVD) from a WF₆/C₃H₈/H₂ mixture at 1173 K. A method to pattern CVD-tungsten carbide is suggested. TEM analysis of as deposited samples displayed a clear and unreacted interface. The electrical investigations of the p-type 6H-SiC Schottky contacts revealed a high rectification ratio and a low reverse current density (6.1 × 10⁻⁵ A cm⁻², −10 V) up to 773 K. On n-type, a low barrier (Φ_Bn=0.79 eV) at room temperature was observed. The low Φ_Bn value suggests WC to be promising as an ohmic contact material on highly doped n-type epi-layers. We will show a temperature dependence for the barrier height of tungsten carbide contacts that can be related to the simultaneous change in the energy bandgap, which should be considered when designing SiC devices intended for high temperature operation.     

Polylactide‐block‐Polypeptide‐block‐Polylactide Copolymer Nanoparticles with Tunable Cleavage and Controlled Drug Release

A versatile nanoparticle system is presented in which drug release is triggered by enzymatic polymer cleavage, resulting in a physicochemical change of the carrier. The polylactide‐block‐peptide‐block‐polylactide triblock copolymer is generated by initiation of the ring‐opening polymerization of L‐lactide with a complex bifunctional peptide having an enzymatic recognition and cleavage site (Pro‐Leu‐Gly‐Leu‐Ala‐Gly). This triblock copolymer is specifically bisected by matrix metalloproteinase‐2 (MMP‐2), an enzyme overexpressed in tumor tissues. Triblock copolymer nanoparticles formed by nonaqueous emulsion polymerization are readily transferred into aqueous media without aggregation, even in the presence of blood serum. Cleavage of the triblock copolymer leads to a significant decrease of the glass transition temperature (T_g) from 39 °C to 31 °C, likely mediating cargo release under physiological conditions. Selective drug targeting is demonstrated by hampered mitosis and increased cell death resulting from drug release via MMP‐2 specific cleavage of triblock copolymer carrier. On the contrary, nanocarriers having a scrambled (non‐recognizable) peptide sequence do not cause enhanced cytotoxicity, demonstrating the enzyme‐specific cleavage and subsequent drug release. The unique physicochemical properties, cleavage‐dependent cargo release, and tunability of carrier bioactivity by simple peptide exchange highlight the potential of this polymer‐nanoparticle concept as platform for custom‐designed carrier systems.