TY - JOUR AB - Proteins of the ARGONAUTE family are important in diverse posttranscriptional RNA-mediated gene-silencing systems as well as in transcriptional gene silencing in Drosophila and fission yeast and in programmed DNA elimination in Tetrahymena. We cloned ARGONAUTE4 (AGO4) from a screen for mutants that suppress silencing of the Arabidopsis SUPERMAN(SUP) gene. The ago4-1 mutant reactivated silentSUP alleles and decreased CpNpG and asymmetric DNA methylation as well as histone H3 lysine-9 methylation. In addition,ago4-1 blocked histone and DNA methylation and the accumulation of 25-nucleotide small interfering RNAs (siRNAs) that correspond to the retroelement AtSN1. These results suggest that AGO4 and long siRNAs direct chromatin modifications, including histone methylation and non-CpG DNA methylation. AU - Zilberman, Daniel AU - Cao, Xiaofeng AU - Jacobsen, Steven E. ID - 9455 IS - 5607 JF - Science KW - Multidisciplinary SN - 0036-8075 TI - ARGONAUTE4 control of locus-specific siRNA accumulation and DNA and histone methylation VL - 299 ER - TY - CONF AB - Discounting the future means that the value, today, of a unit payoffis 1 if the payoffo ccurs today, a if it occurs tomorrow, a 2 if it occurs the day after tomorrow, and so on, for some real-valued discount factor 0 < a < 1. Discounting (or inflation) is a key paradigm in economics and has been studied in Markov decision processes as well as game theory. We submit that discounting also has a natural place in systems engineering: for nonterminating systems, a potential bug in the far-away future is less troubling than a potential bug today. We therefore develop a systems theory with discounting. Our theory includes several basic elements: discounted versions of system properties that correspond to the ω-regular properties, fixpoint-based algorithms for checking discounted properties, and a quantitative notion of bisimilarity for capturing the difference between two states with respect to discounted properties. We present the theory in a general form that applies to probabilistic systems as well as multicomponent systems (games), but it readily specializes to classical transition systems. We show that discounting, besides its natural practical appeal, has also several mathematical benefits. First, the resulting theory is robust, in that small perturbations of a system can cause only small changes in the properties of the system. Second, the theory is computational, in that the values of discounted properties, as well as the discounted bisimilarity distance between states, can be computed to any desired degree of precision. AU - De Alfaro, Luca AU - Henzinger, Thomas A AU - Majumdar, Ritankar ID - 4628 SN - 9783540404934 T2 - Proceedings of the 30th International Colloquium on Automata, Languages and Programming TI - Discounting the future in systems theory VL - 2719 ER - TY - JOUR AB - Cross-metathesis reactions of α,β-unsaturated sulfones and sulfoxides in the presence of molybdenum and ruthenium pre-catalysts were tested. A selective metahesis reaction was achieved between functionalized terminal olefins and vinyl sulfones by using the ‘second generation’ ruthenium catalysts 1c–h while the highly active Schrock catalyst 1b was found to be functional group incompatible with vinyl sulfones. The cross-metathesis products were isolated in good yields with an excellent (E)-selectivity. Both the molybdenum and ruthenium-based complexes were, however, incompatible with α,β- and β,γ-unsaturated sulfoxides. AU - Michrowska, Anna AU - Bieniek, Michał AU - Kim, Mikhail AU - Klajn, Rafal AU - Grela, Karol ID - 13436 IS - 25 JF - Tetrahedron KW - Organic Chemistry KW - Drug Discovery KW - Biochemistry SN - 0040-4020 TI - Cross-metathesis reaction of vinyl sulfones and sulfoxides VL - 59 ER - TY - CONF AB - We present a formalism for specifying component interfaces that expose component requirements on limited resources. The formalism permits an algorithmic check if two or more components, when put together, exceed the available resources. Moreover, the formalism can be used to compute the quantity of resources necessary for satisfying the requirements of a collection of components. The formalism can be instantiated in several ways. For example, several components may draw power from the same source. Then, the formalism supports compatibility checks such as: can two components, when put together, achieve their tasks without ever exceeding the available amount of peak power? or, can they achieve their tasks by using no more than the initially available amount of energy (i.e., power accumulated over time)? The corresponding quantitative questions that our algorithms answer are the following: what is the amount of peak power needed for two components to be put together? what is the corresponding amount of initial energy? To solve these questions, we model interfaces with resource requirements as games with quantitative objectives. The games are played on state spaces where each state is labeled by a number (representing, e.g., power consumption), and a play produces an infinite path of labels. The objective may be, for example, to minimize the largest label that occurs during a play. We illustrate our approach by modeling compatibility questions for the components of robot control software, and of wireless sensor networks. AU - Chakrabarti, Arindam AU - De Alfaro, Luca AU - Henzinger, Thomas A AU - Stoelinga, Mariëlle ID - 4561 SN - 9783540202233 T2 - Third International Conference on Embedded Software TI - Resource interfaces VL - 2855 ER - TY - CONF AB - We consider concurrent two-person games played in real time, in which the players decide both which action to play, and when to play it. Such timed games differ from untimed games in two essential ways. First, players can take each other by surprise, because actions are played with delays that cannot be anticipated by the opponent. Second, a player should not be able to win the game by preventing time from diverging. We present a model of timed games that preserves the element of surprise and accounts for time divergence in a way that treats both players symmetrically and applies to all ω-regular winning conditions. We prove that the ability to take each other by surprise adds extra power to the players. For the case that the games are specified in the style of timed automata, we provide symbolic algorithms for their solution with respect to all ω-regular winning conditions. We also show that for these timed games, memory strategies are more powerful than memoryless strategies already in the case of reachability objectives. AU - De Alfaro, Luca AU - Faella, Marco AU - Henzinger, Thomas A AU - Majumdar, Ritankar AU - Stoelinga, Mariëlle ID - 4630 SN - 9783540407539 T2 - Proceedings of the 14th International Conference on Concurrency Theory TI - The element of surprise in timed games VL - 2761 ER -