Successful long-term ventricular pacing via the coronary sinus after the Fontan operation

A man with double inlet left ventricle and severe subpulmonary stenosis underwent a Fontan operation at the age of 29 years. Eight years later he developed atrial flutter with complete heart block. To avoid a further thoracotomy, a unipolar carbon tipped electrode was placed into the posterior cardiac vein via the coronary sinus. More than 8 years after implantation of the original lead, and after two generator changes, telemetric thresholds remain between 1.8-2.1 volts. Percutaneous transvenous ventricular pacing via the coronary sinus can produce an excellent long-term result and should be the initial approach of choice after a Fontan-type operation.     

Micro-persistence and difficulty in a game-based learning environment for computational thinking acquisition

Persistence has been identified as a crucial quality of learning. However, it is hard to attain in online game-based environments as the drive to progress in the game may influence the ability to achieve the learning goals. This study aimed to examine the associations between micro-persistence, that is, the tendency to complete an individual task successfully, and task difficulty while acquiring computational thinking (CT). We further explored whether contextual or personal attributes better explain micro-persistence. We analysed data of 111 school students who used the CodeMonkey platform. We took a learning analytics approach for analysing the platform's log files. We found that micro-persistence is associated with task difficulty and that students who demonstrated an aptitude to learn new material are motivated to achieve the best solution. We also found that contextual variables better-explained micro-persistence than personal attributes. Encouraging micro-persistence can improve CT acquisition and the learning processes involved.     

The expected complexity of analytic tableaux analyses in propositional calculus — II

The article continues a study of the complexity of an analytic tableaux algorithm for SAT. The main result is that the average number of branches in analytic tableaux of formulae of lengthn is((1.09988...) ⁿ ). The maximum number of branches is also studied. Both the average and worst case complexity measures are used to compare analytic tableaux and truth tables.For the average case result the precise number of consistent branches and the precise number of inconsistent branches (for formulae of lengthn) are each expressed as multiply indexed sums whose terms involve factorials and Stirling numbers of the second kind. The asymptotic behavior of these sums is determined by adapting a classical technique for determining the asymptotic behavior of singly indexed sums whose terms involve factorials.     

Comprehensibility of UML-based software product line specifications

Software Product Line Engineering (SPLE) deals with developing artifacts that capture the common and variable aspects of software product families. Domain models are one kind of such artifacts. Being developed in early stages, domain models need to specify commonality and variability and guide the reuse of the artifacts in particular software products. Although different modeling methods have been proposed to manage and support these activities, the assessment of these methods is still in an inceptive stage. In this work, we examined the comprehensibility of domain models specified in ADOM, a UML-based SPLE method. In particular, we conducted a controlled experiment in which 116 undergraduate students were required to answer comprehension questions regarding a domain model that was equipped with explicit reuse guidance and/or variability specification. We found that explicit specification of reuse guidance within the domain model helped understand the model, whereas explicit specification of variability increased comprehensibility only to a limited extent. Explicit specification of both reuse guidance and variability often provided intermediate results, namely, results that were better than specification of variability without reuse guidance, but worse than specification of reuse guidance without variability. All these results were perceived in different UML diagram types, namely, use case, class, and sequence diagrams and for different commonality-, variability-, and reuse-related aspects.     

Repeated Budgeted Second Price Ad Auction

Our main goal is to abstract existing repeated sponsored search ad auction mechanisms which incorporate budgets, and study their equilibrium and dynamics. Our abstraction has multiple agents bidding repeatedly for multiple identical items (such as impressions in an ad auction). The agents are budget limited and have a value per item. We abstract this repeated interaction as a one-shot game, which we call budget auction, where agents submit a bid and a budget, and then items are sold by a sequential second price auction. Once an agent exhausts its budget it does not participate in the proceeding auctions. Our main result shows that if agents bid conservatively (never bid above their value) then there always exists a pure Nash equilibrium. We also study simple dynamics of repeated budget auctions, showing their convergence to a Nash equilibrium for two agents and for multiple agents with identical budgets.     

Crystallization of crystalline/crystalline blends: Polypropylene/polybutene-1

The crystallization, from molten blends, of polypropylene (PP) and polybutene-1 (PB), two highly crystallizable, polymers, their interaction in the amorphous phase, and the resulting tensile mechanical properties were studied. The crystallization was followed by DSC, showing two separate PP and PB crystallization processes which are affected each by the presence of the other component. The crystallization temperature of PP is significantly affected only in PB rich blends whereas that of PB is affected in the whole composition range. The PP crystalline phase, acting as a nucleating agent, increases the PB crystallization temperature whereas the PP amorphous phase, acting as a high viscosity polymeric diluent, reduces the PB crystallization temperature. The first effect is dominant at low PP content, and the second one becomes increasingly effective with increasing PP content in the blend. The interaction between the two polymers in the amorphous phase was studied by applying dynamic mechanical analysis, in which a single glass transition was observed for the blends and its temperature was found to vary with the blends' composition. Tensile mechanical properties of blends were found to be more sensitive to thermal treatments, such as isothermal crystallization or annealing at elevated temperatures, than single component systems. Such thermal treatments enable better structured blends to be formed, resulting in mechanical properties with no abrupt changes in the whole composition range.     

Air sampling of volatile sex pheromone components in a closed jar

A cotton wool plug, used as the source for pheromone release, was placed in closed 1-quart Mason jars, either at the mouth or at the rear of the jar. Air sampling of the two components of the sex pheromone (total 2.2 mg at the source) of the almond moth (Ephestia cautella) female showed that the saturation period near the source in still air was 20–22 hr and that far from the source was 40–50 hr, reaching a level of less than 1 ng/ml air. The ratio between the components (Z,E)-9,12-tetradecadienyl acetate, designated D, and (Z)-9-tetradecenyl acetate designated M, in the air was close to the original ratio for both sampling sites, albeit somewhat richer in the more volatile (Z)-9-tetradecenyl acetate (source 77.023.0 DM, air 73.0– 74.327.0–25.7; source 80.119.9, air 77.622.4; source 25.174.9, air 23.976. 1 DM). The total amount of pheromone per milliliter of air was two to three times larger near the source than far from it at the early stages of the evaporation and saturation process. When the amount of pheromone applied to the source was tripled (7 mg), the amount far from the source was almost tripled, or the saturation time was cut by factor of two to three.     

Distributed envy minimization for resource allocation

Minimizing envy in distributed discrete resource or task allocation, is an unusual distributed optimization challenge, since the quality of the allocation for each of the agents is dependent, not only on its own allocation, but on the allocation of others as well. Thus, in order to perform distributed search for allocations with minimal envy there is a need to design innovative algorithms that can cope with the challenging constraint structure of an envy minimization problem. Distributed methods for minimizing envy among agents in indivisible resource allocation problems are presented. First, Distributed Envy Minimization Problems (DEMP) are formulated as Distributed Constraint Reasoning problems. When the DEMPs are large, and cannot be solved by a complete search an incomplete local search algorithm is presented. Each transfer of a good from one agent to another involves the change of state of more than one agent. Thus, a minimizing envy local search algorithm must build upon actions (transfers) that include multiple agents. Since DEMPs are particularly susceptible to local minima during local search, the paper proposes an algorithm that alternates between two different hill climbing search phases. The first phase uses one-transfer steps while the other exploits envy cycle elimination steps. An algorithm that minimizes envy while preserving efficiency, is proposed. The proposed algorithm finds a Pareto optimal allocation with low envy. In the context of resource allocation problems, a Pareto optimal solution is particularly desirable since it presents a stable solution. The proposed algorithm first finds a divisible Pareto optimal envy-free allocation using a Fisher market equilibrium. This allocation is transferred into an indivisible allocation of goods while maintaining the Pareto optimal characteristic of the allocation and a low envy level among agents.