Communicating Processes with Data for Supervisory Coordination

We employ supervisory controllers to safely coordinate high-level discrete(-event) behavior of distributed components of complex systems. Supervisory controllers observe discrete-event system behavior, make a decision on allowed activities, and communicate the control signals to the involved parties. Models of the supervisory controllers can be automatically synthesized based on formal models of the system components and a formalization of the safe coordination (control) requirements. Based on the obtained models, code generation can be used to implement the supervisory controllers in software, on a PLC, or an embedded (micro)processor. In this article, we develop a process theory with data that supports a model-based systems engineering framework for supervisory coordination. We employ communication to distinguish between the different flows of information, i.e., observation and supervision, whereas we employ data to specify the coordination requirements more compactly, and to increase the expressivity of the framework. To illustrate the framework, we remodel an industrial case study involving coordination of maintenance procedures of a printing process of a high-tech Oce printer.Comment: In Proceedings FOCLASA 2012, arXiv:1208.432

Modelling Clock Synchronization in the Chess gMAC WSN Protocol

We present a detailled timed automata model of the clock synchronization algorithm that is currently being used in a wireless sensor network (WSN) that has been developed by the Dutch company Chess. Using the Uppaal model checker, we establish that in certain cases a static, fully synchronized network may eventually become unsynchronized if the current algorithm is used, even in a setting with infinitesimal clock drifts

A Process Algebra for Supervisory Coordination

A supervisory controller controls and coordinates the behavior of different components of a complex machine by observing their discrete behaviour. Supervisory control theory studies automated synthesis of controller models, known as supervisors, based on formal models of the machine components and a formalization of the requirements. Subsequently, code generation can be used to implement this supervisor in software, on a PLC, or embedded microprocessor. In this article, we take a closer look at the control loop that couples the supervisory controller and the machine. We model both event-based and state-based observations using process algebra and bisimulation-based semantics. The main application area of supervisory control that we consider is coordination, referred to as supervisory coordination, and we give an academic and an industrial example, discussing the process-theoretic concepts employed.Comment: In Proceedings PACO 2011, arXiv:1108.145

Reactions of (1,3,3-Trichloro-2,2,4,4-tetramethylcyclobutyl)sulfenyl Chloride with Some S- and O-Nucleophiles

The sterically crowded 3,3-trichloro-2,2,4,4-tetramethylcyclobutanethione (2c) easily reacts with phosphorus pentachloride in CCl4 yielding the relatively stable (1,3,3-trichloro-2,2,4,4-tetramethylcyclobutyl)sulfenyl chloride (3c). The reactions of 3c with benzylsulfane (4) and thiocamphor (5) occur with elimination of HCl leading to the unsymmetrical disulfanes 6 and 9. In the case of the sulfenates 10 and 12, which are formed as intermediates in the reactions of 3c with propargyl and allyl alcohol, respectively, the subsequent [2,3]-sigmatropic rearrangement yields the corresponding sulfoxides 11 and 13

KCu(SeO₄)Cl(H₂O)₂, a first copper chloride selenate

Abstract A first copper chloride selenate was obtained upon attempted preparation of a selenate analog of chlorothionite. The new compound is monoclinic, P21/c, a = 7.1833(5) Å, b = 11.7784(8) Å, c = 8.2419(6) Å, β = 91.083(2)°, V = 697.20(8) Å3, R 1 = 0.033. KCu(SeO4)Cl(H2O)2 has no structural analogs and adds to the small family of transition metal selenate halides. The CuO3(H2O)2Cl strongly distorted octahedra share common O–O edges thus forming dimeric units with a Cu–Cu distance of 3.49 Å. Dimeric units and SeO4 tetrahedra in KCu(SeO4)Cl(H2O)2 share common O atoms to produce unique [Cu(SeO4)Cl(H2O)2]− chains. We discuss further perspectives of the selenate halide family and expected differences in crystal chemistry of sulfate and selenate halides.</jats:p

Layered calcium hydrogen selenite chlorides Ca(HSeO₃)Cl and Ca(HSeO₃)Cl(H₂O), the first halides obtained in СaCl₂–H₂SeO₃–H₂O system

Abstract Synthesis, crystal structures and IR spectra of the first representatives of calcium hydrogen selenite halides are reported. Colourless prismatic crystals of calcium hydrogen selenite chloride Ca(HSeO3)Cl and corresponding hydrated analogue Ca(HSeO3)Cl(H2O) were produced upon evaporation of aqueous solutions. Ca(HSeO3)Cl is monoclinic, P21/c, a = 7.0031(11) Å, b = 7.7336(12) Å, c = 8.5024(13) Å, β = 109.889(3)°, V = 433.02(12) Å3, R 1 = 0.039. Ca(HSeO3)Cl(H2O) is orthorhombic, Pbca, a = 6.222(4) Å, b = 10.413(7) Å, c = 16.875(10) Å, V = 1093.3 (12) Å3, R 1 = 0.041. Ca(HSeO3)Cl and Ca(HSeO3)Cl(H2O) represent new structure types. In both structures, Ca2+ cations adopt mixed-ligand environments formed by oxygen atoms of hydrogen selenite anions (and water molecules for Ca(HSeO3)Cl(H2O)) and chloride ions. Both structures are layered. The crystal structure of Ca(HSeO3)Cl(H2O) demonstrates a rare phenomenon of hydrogen-bonded assembly of water and chloride in the interlayer space.</jats:p

Copper hydroselenite nitrates (<i>A</i> ⁺NO₃)<i> _n </i> [Cu(HSeO₃)₂] (<i>A</i>=Rb⁺, Cs⁺ and Tl⁺, <i>n</i>=1, 2) related to Ruddlesden – Popper phases

Abstract Three new layered copper hydrogen selenite nitrates, (ANO3)[Cu(HSeO3)2] (A = Cs, and Tl), and (RbNO3)2[Cu(HSeO3)2] have been prepared via isothermal evaporation of concentrated nitric acid solutions. The Tl and Cs compounds adopt a motif related to previously known (NH4Cl)[Cu(HSeO3)2]; the structure of the Rb compound represents a new structure type. The structures of (ANO3)[Cu(HSeO3)2] (A = Cs, Tl), (RbNO3)2[Cu(HSeO3)2], and (NH4NO3)3[Cu(HSeO3)2] form a unique homological series distantly related to Ruddlesden – Popper series of layered perovskites.</jats:p

Hsp90 of <i>E. coli</i> modulates assembly of FtsZ, the bacterial tubulin homolog

Significance Hsp90 is a molecular chaperone that participates in protein remodeling and activation. We previously demonstrated that Hsp90 causes cell filamentation when highly expressed in E. coli . Here we show that cells filament due to overexpression of Hsp90 Ec because FtsZ, a bacterial tubulin homolog essential for cell division, fails to assemble into FtsZ rings. In vitro, Hsp90 Ec interacts with FtsZ and inhibits FtsZ polymerization. Moreover, E. coli deleted for the Hsp90 Ec gene, htpG , turn over FtsZ more rapidly than wild-type cells, and the length of Δ htpG cells is reduced compared to wild-type cells. Altogether, these results suggest that Hsp90 Ec is a modulator of cell division, and imply that the polypeptide-holding function of Hsp90 may be a biologically important chaperone activity. </jats:p

Molecular inorganic polymers: synthesis and crystal structures of KCl72H₂SeO₃ and CsCl7H₂SeO₃

Abstract KCl72H2SeO3 and CsCl7H2SeO3 have been synthesized using solution evaporation methods from aqueous solution. Both compounds are monoclinic (P2/n and P21/c) and demonstrate new structure types. One symmetrically unique SeO(OH)2 molecule is present in each structure. SeO(OH)2 molecules via strong hydrogen bonds form chains in KCl72H2SeO3 and layers in ?sCl7H2SeO3. The structures of KCl72H2SeO3 and CsCl7H2SeO3 can be described as consisting of ionic KCl chains and CsCl layers incorporated into the covalent- and hydrogen-bonded H2SeO3 matrix. To the best of our knowledge, the cases when selenious acid acts as a contributor to the molecular building blocks of salt-inclusion structures are not known to date.</jats:p

Influence of the alkali cation size on the Cu²⁺ coordination environments in (<i>AX</i>)[Cu(HSeO₃)₂] (<i>A</i>=Na, K, NH₄, Rb, Cs; <i>X</i>=Cl, Br) layered copper hydrogen selenite halides

Abstract Using solution evaporation techniques, we succeeded in preparation of new members essentially extending the layered copper hydrogen selenite family, (AX)[Cu(HSeO3)2] with A = Na, K, Rb, Cs, and NH4, and X = Cl and Br. Bromides and chlorides are isostructural in the family of described new compounds crystallizing in three different structure types. (NaX)[Cu(HSeO3)2] and (KX)[Cu(HSeO3)2] (X = Cl, Br) are monoclinic, whereas (AX)[Cu(HSeO3)2] (A = NH4, Rb, Cs; X = Cl, Br) are orthorhombic. Upon the enlargement of the A + ionic radii inserted in the interlayer between the neighboring [Cu(HSeO3)2] slabs, the effective distance is increasing and results in essential elongation of the apical Cu-X (X = Cl, Br) distances. Three different types of CuO4 X n (n = 0–2) polyhedra are formed. The observed trend is an interesting example of the chemical tuning of the Cu2+ coordination environments.</jats:p