Lower Bounds Against Weakly-Uniform Threshold Circuits

An ongoing line of research has shown super-polynomial lower bounds for uniform and slightly-non-uniform small-depth threshold and arithmetic circuits (Allender, in Chicago J. Theor. Comput. Sci. 1999(7), 1999; Koiran and Perifel, in Proceedings of the 24th Annual IEEE Conference on Computational Complexity (CCC 2009), pp. 35–40, 2009; Jansen and Santhanam, in Proceedings of the 38th International Colloquium on Automata, Languages and Programming (ICALP 2011), I, pp. 724–735, 2011). We give a unified framework that captures and improves each of the previous results. Our main results are that Permanent does not have threshold circuits of the following kinds.

1. Depth O(1), n ^o(1) bits of non-uniformity, and size n ^O(1).
2. Depth O(1), polylog(n) bits of non-uniformity, and size s(n) such that for all constants c the c-fold composition of s, s ^(c)(n), is less than 2 ⁿ .
3. Depth o(loglogn), polylog(n) bits of non-uniformity, and size n ^O(1).

(1) strengthens a result of Jansen and Santhanam (Jansen and Santhanam, in Proceedings of the 38th International Colloquium on Automata, Languages and Programming (ICALP 2011), I, pp. 724–735, 2011), who obtained similar parameters but for arithmetic circuits of constant depth rather than Boolean threshold circuits. (2) and (3) strengthen results of Allender (Allender, in Chicago J. Theor. Comput. Sci. 1999(7), 1999) and Koiran and Perifel (Koiran and Perifel, in Proceedings of the 24th Annual IEEE Conference on Computational Complexity (CCC 2009), pp. 35–40, 2009), respectively, who obtained results with similar parameters but for completely uniform circuits. Our main technical contribution is to simplify and unify earlier proofs in this area, and adapt the proofs to handle some amount of non-uniformity. We also develop a notion of circuits with a small amount of non-uniformity that naturally interpolates between fully uniform and fully non-uniform circuits. We use this notion, which we term weak uniformity, rather than the earlier and essentially equivalent notion of succinctness used by Jansen and Santhanam because the notion of weak uniformity more fully and easily interpolates between full uniformity and non-uniformity of circuits.     

Fine-grained integration of access control policies

Collaborative and distributed applications, such as dynamic coalitions and virtualized grid computing, often require integrating access control policies of collaborating parties. Such an integration must be able to support complex authorization specifications and the fine-grained integration requirements that the various parties may have. In this paper, we introduce an algebra for fine-grained integration of sophisticated policies. The algebra, which consists of three binary and two unary operations, is able to support the specification of a large variety of integration constraints. For ease of use, we also introduce a set of derived operators and provide guidelines for users to edit a policy with desired properties. To assess the expressive power of our algebra, we define notion of completeness and prove that our algebra is complete and minimal with respect to the notion. We then propose a framework that uses the algebra for the fine-grained integration of policies expressed in XACML. We also present a methodology for generating the actual integrated XACML policy, based on the notion of Multi-Terminal Binary Decision Diagrams. Experimental results have demonstrated both effectiveness and efficiency of our approach. In addition, we also discuss issues regarding obligations.     

Technical Efficiency of European Metro Systems: The Effects of Operational Management and Socioeconomic Environment

This study focuses on the relationship between the operational performance of metro systems and their socioeconomic contexts. We use a two-stage methodology applied to a sample of 17 European metro systems. First, we apply a stochastic frontier approach to establish the optimal production function and to evaluate the efficiency and effectiveness levels of each firm through offer and demand-characterizing indicators, respectively. Only internal production factors are included in the first stage of this analysis. In a second stage, we use a similar modeling approach, but considering an additional set of variables characterizing the socioeconomic environment of the urban areas in which metro systems operate. This method allows observing the effects on operational performance measurements due to the inclusion of external factors, and consequently, drawing some conclusions on the technical efficiency of metro systems and their operations in beneficial or adverse surrounding environments. Different scores resulting from both perspectives evidence the contributions of the socioeconomic factors to improve the reliability of performance measurements and to reduce false inefficiencies. The results show that 12 of the analyzed systems are being affected by an unfavourable socioeconomic environment and/or their network suffers from some adequacy problems with regard to demand. The remaining five systems should improve their management strategies, since their results are being supported by a favourable surrounding environment.     

Influence of Dissolution Medium Agitation on Release Profiles of Sustained-Release Tablets

Reaching nearly perfect sink conditions is very important in the determination of drug dissolution rates. Many times, the only factor that is taken into consideration in achieving sink conditions is the relation between the drug concentration and its solubility. The analytical conditions of the dissolution assay, as well as the dissolution apparatus, stirring speed, and nature and volume of the dissolution fluid may also influence the dissolution results. The main objective of this work was to study the influence of the stirring rate conditions and of the dissolution apparatus in the diltiazem hydrochloride release from tablets. Diltiazem hydrochloride sustained-release (SR) tablets were tested and the following dissolution parameters were evaluated: t_10%, t_25%, t_50%, dissolution time, mean dissolution time (MDT), and dissolution efficiency (DE) at t₁₂₀, and at t₃₆₀. To analyze the release mechanism, several release models were tested, such as Higuchi, zero order, first order, Baker-Lonsdale, Hixson-Crowell, Weibull, and Korsmeyer-Peppas. The similarities between two in vitro dissolution profiles were assessed by the similarity factor f₂. The in vitro release kinetics of diltiazem hydrochloride sustained-release tablets were evaluated using the USP 2 (paddle) and USP 4 (flow-through) apparatus.     

Daily egg consumption in hyperlipidemic adults - Effects on endothelial function and cardiovascular risk

Background  

Limiting consumption of eggs, which are high in cholesterol, is generally recommended to reduce risk of cardiovascular disease. However, recent evidence suggests that dietary cholesterol has limited influence on serum cholesterol or cardiac risk.     

The socio-political economy of nuclear power development in Japan and South Korea

This paper analyzes the socio-cultural, political and economic conditions prevalent during the inception of nuclear power programs in Japan and South Korea in order to identify commonalities which support nuclear power program expansion. The study identifies six factors as having a clear influence on supporting nuclear power development: (1) strong state involvement in guiding economic development; (2) centralization of national energy policymaking and planning; (3) campaigns to link technological progress with national revitalization; (4) influence of technocratic ideology on policy decisions; (5) subordination of challenges to political authority, and (6) low levels of civic activism. The paper postulates that insights from this study can be used to assess the propensity of nations which have the emergent capacity to support nuclear power development to actually embark on such programs.     

Design of a novel biohythane process with high H2 and CH4 production rates

A biohythane process based on wheat straw including: i) pretreatment, ii) H₂ production using Caldicellulosiruptor saccharolyticus, iii) CH₄ production using an undefined consortium, and iv) gas upgrading using an amine solution, was assessed through process modelling including cost and energy analysis. According to simulations, a biohythane gas with the composition 46–57% H₂, 43–54% CH₄ and 0.4% CO₂, could be produced at high production rates (2.8–6.1 L/L/d), with 93% chemical oxygen demand (COD) reduction, and a net energy yield of 7.4–7.7 kJ/g dry straw. The model was calibrated and verified using experimental data from dark fermentation (DF) of wheat straw hydrolysate, and anaerobic digestion of DF effluent. In addition, the effect of gas recirculation was investigated by both wet experiments and simulation. Sparging improved H₂ productivities and yields, but negatively affected the net energy gain and cost of the overall process.