Which Classes of Origin Graphs Are Generated by Transducers.

We study various models of transducers equipped with origin information. We consider the semantics of these models as particular graphs, called origin graphs, and we characterise the families of such graphs recognised by streaming string transducers

Undecidability of a weak version of MSO+U

We prove the undecidability of MSO on ω-words extended with the second-order predicate U1(X) which says that the distance between consecutive positions in a set X⊆N is unbounded. This is achieved by showing that adding U1 to MSO gives a logic with the same expressive power as MSO+U, a logic on ω-words with undecidable satisfiability. As a corollary, we prove that MSO on ω-words becomes undecidable if allowing to quantify over sets of positions that are ultimately periodic, i.e., sets X such that for some positive integer p, ultimately either both or none of positions x and x+p belong to X

Weighted One-Deterministic-Counter Automata

We introduce weighted one-deterministic-counter automata (ODCA). These are weighted one-counter automata (OCA) with the property of counter-determinacy, meaning that all paths labelled by a given word starting from the initial configuration have the same counter-effect. Weighted ODCAs are a strict extension of weighted visibly OCAs, which are weighted OCAs where the input alphabet determines the actions on the counter. We present a novel problem called the co-VS (complement to a vector space) reachability problem for weighted ODCAs over fields, which seeks to determine if there exists a run from a given configuration of a weighted ODCA to another configuration whose weight vector lies outside a given vector space. We establish two significant properties of witnesses for co-VS reachability: they satisfy a pseudo-pumping lemma, and the lexicographically minimal witness has a special form. It follows that the co-VS reachability problem is in P. These reachability problems help us to show that the equivalence problem of weighted ODCAs over fields is in P by adapting the equivalence proof of deterministic real-time OCAs by B\"ohm et al. This is a step towards resolving the open question of the equivalence problem of weighted OCAs. Furthermore, we demonstrate that the regularity problem, the problem of checking whether an input weighted ODCA over a field is equivalent to some weighted automaton, is in P. Finally, we show that the covering and coverable equivalence problems for uninitialised weighted ODCAs are decidable in polynomial time. We also consider boolean ODCAs and show that the equivalence problem for (non-deterministic) boolean ODCAs is in PSPACE, whereas it is undecidable for (non-deterministic) boolean OCAs.Comment: 36 pages, 11 figure

On synthesis of resynchronizers for transducers

We study two formalisms that allow to compare transducers over words under origin semantics: rational and regular resynchronizers, and show that the former are captured by the latter. We then consider some instances of the following synthesis problem: given transducers T_1,T_2, construct a rational (resp. regular) resynchronizer R, if it exists, such that T_1 is contained in R(T_2) under the origin semantics. We show that synthesis of rational resynchronizers is decidable for functional, and even finite-valued, one-way transducers, and undecidable for relational one-way transducers. In the two-way setting, synthesis of regular resynchronizers is shown to be decidable for unambiguous two-way transducers. For larger classes of two-way transducers, the decidability status is open

Constrained Dynamic Tree Networks

We generalise Constrained Dynamic Pushdown Networks, introduced by Bouajjani\et al, to Constrained Dynamic Tree Networks.<br>In this model, we have trees of processes which may monitor their children.<br>We allow the processes to be defined by any computation model for which the alternating reachability problem is decidable.<br>We address the problem of symbolic reachability analysis for this model. More precisely, we consider the problem of computing an effective representation of their reachability<br>sets using finite state automata. <div>We show that backwards reachability sets starting from regular sets of configurations are always regular. </div><div>We provide an algorithm for computing backwards reachability sets using tree automata.<br><br></div

Reactivity of electrophilic reagents towards silyl enol ether groups incorporated into vinyl polymers

Vinyl polymers containing about 20 mol-% of trimethylsilyl or tertbutyldimethylsilyl enol ether functionalities were synthesized by copolymerizing styrene or methyl methacrylate with either 2-trimethylsiloxybutadiene or 2-(tertbutyldimethysiloxy)butadiene under classical free-radical polymerization conditions. The reactivity of the resulting polymers toward a set of classical electrophilic reagents was investigated. Selected electrophiles included water, p-toluenesulfonyl isocyanate ([2+2]-cycloaddition), aromatic and aliphatic aldehydes (aldol reaction), benzaldehyde dimethyl acetal (Noyori condensation), and bromine. Detailed analysis of the polymer final structure - including quantitative H-1- and C-13-NMR analysis - demonstrated that in most cases the silyl enol ether group displays the same reactivity pattern as low-molecular weight analogs. (C) 1997 Elsevier Science Ltd

Reactive polymers incorporating silyl enol ether groups. 3 - Incorporation of alpha,beta-bis(siloxy)vinylene units into the backbone of vinyl polymers by free-radical (co)polymerization of 2,3-bis(trialkylsiloxy)butadienes

2,3-Bis(trimethylsiloxy)butadiene (1) and 2,3-bis(tert-butyldimethylsiloxy)butadiene (2) have been homopolymerized and copolymerized with styrene (St) and methyl methacrylate (MMA) under free-radical conditions. Comparison of initial rates and molecular weights with polymerizations conducted under identical experimental conditions on monosubstituted analogs, 2-trimethysiloxybutadiene (3) and 2-(tert-butyldimethylsiloxy)butadiene (4), demonstrated that the second substituent does not decrease the polymerizability significantly despite the additional steric hindrance introduced in the monomer. Extensive H-1 and C-13 NMR characterization of the polymers demonstrated that the main incorporation mode is of the 1,4-type, allowing more than 95% of the butadienyl subunit to be incorporated in the main chain as an alpha,beta-bis(trialkylsiloxy)vinylene functional group. Monomer reactivity ratios r(1) and r(2) at 60 degrees C were determined from copolymer composition curves obtained at low conversions and are compared with values obtained for other 1,2-butadienyl systems

Synthesis and 500 Mhz-nmr Characterization of Poly(2-trimethylsiloxy)butadiene Obtained By Free-radical and Cationic Polymerizations

2-(Trimethylsiloxy)butadiene was polymerized in the presence of AIBN, using different conditions of dilution and temperature. The resulting polymer was characterized by H-1- and C-13-NMR: in particular, DEPT and H-1-C-13 correlation spectra allowed to assign the different microstructures with high confidence. Cis- and trans-1,4-microstructures and 3,4-microstructure were observed in all cases, but 1,2-microstructure was never detected. The evolution of microstructure ratios with temperature was found to differ from the evolution described for other 2-substituted butadienes. Molecular weights determined by GPC are low to moderate in all cases (M(n) < 10(4)) decreasing with increasing temperature. Attempts to polymerize the monomer in the presence of cationic initiators failed to give a polymer, except when SnCl4 was used

Main Glucosidase Conversion Products of the Gluco-Alkaloids Dolichantoside and Palicoside

The enzymatic glucose cleavage of palicoside revealed the biosynthetic pathway to akagerine, whereas the conversion of dolichantoside led to a new quaternary heteroyohimbine alkaloid named N(b)-methyl-21-beta-hydroxy-mayumbine. The hypothetical models of reactions occurring after the conversion of both substrates are proposed. Dolichantoside and palicoside, as well as Strychnos mellodora stem bark crude ethanol extract, exhibit significant antimycotic activity against human pathogens in presence of specific glucosidase