170,393 research outputs found
Conduché property and Tree-based categories
No full textThis paper focuses on a property of enriched functors reflecting the factorisation of morphisms, used in concurrency semantics. According to Lawvere [F.W. Lawvere, State categories and response functors, 1986, Unpublished manuscript], a functor strictly reflecting morphism factorisation induces a notion of state on its domain, when it is considered as a control functor. This intuition works both in case of physical and computing processes [M. Bunge, M.P. Fiore, Unique factorisation lifting functors and categories of linearly-controlled processes, Math. Structures Comput. Sci. 10 (2) 2000 137-163; M.P. Fiore, Fibered models of processes: Discrete, continuous and hybrid systems, in: Proc. of IFIP TCS 2000, in: LNCS, vol. 1872, 2000, pp. 457-473]. In this note we investigate a more general property in the family of models we proposed elsewhere for communicating processes, and we assess their bisimulation relations [S. Kasangian, A. Labella, Observational trees as models for concurrency, Math. Structures. Comput. Sci. 9 (1999) 687-718; R. De Nicola, D. Gorla, A. Labella, Tree-Functors, determinacy and bisimulations, Technical Report, 02/2006, Dip. di Informatica, Univ. di Roma "La Sapienza" (Italy), 2008 (submitted for publication), http://www.dsi.uniroma1.it/%7Egorla/papers/DGL-TR0206.pdf]. Hence, we adapt the notion of "Conduché condition" [F. Conduché, Au sujet de l'existence d'adjoints à droîte aux foncteurs image reciproque dans la catégorie des catégories, C. R. Acad. Sci. Paris 275 (1972) A891-894] to the context of enriched category theory. This notion, weaker than the original "Moebius condition" used by Lawvere, seems to be more suitable for the description of the concurrency models parametrised w.r.t. a base category via the mechanism of change of base, actually. The base category is a monoidal 2-category; a category of generalised trees, T r e e, is obtained from it. We consider Conduché T r e e-based categories, where enrichment reflects factorisation of objects in the base category. We prove that a form of Conduché's theorem holds for Conduché T r e e-functors. We also show how the Conduché condition plays a crucial role in modelling concurrent processes and bisimulations between them. The notions of "state preservation" and "determinacy" [R. Milner, Communication and Concurrency, Prentice Hall International, 1989] are formally characterised. © 2009 Elsevier B.V. All rights reserved
Theoretical Informatics and Applications April 2002 - Volume 36 - Issue 02 (Fixed Points in Computer Science (FICS'01))
No full textThe papers included in this special issue are among the more representative ones presented
at the workshop Fixed Points in Computer Science (FICS’01) which took place in
Florence on September 2001, as a satellite event of PLI’ 01. This was the third workshop
of a series the aim of which is to provide a forum for researchers to present their results
to those members of the computer science and logic communities who study or apply the
fixed point operations in the different fields and formalisms. Previous workshops where
held in 1998 in Brno and in 2000 in Paris (Special issues of these events also appeared in
this journal). The Workshop was sponsored by Dipartimento di Sistemi ed Informatica
of Universita‘di Firenze and Gruppo Nazionale per il Calcolo Scientifico of CNR.
The scientific program of the workshop consisted of 5 invited lectures given by
J. Adamek, Z. ́Esik, I. Guessarian, C. Stirling and R.F.C. Walters, as well as of 12 presentations
chosen, after formal refereeing by the program committe members.
The Program Committee was formed by: J. Adamek, R. Backhouse, S. Bloom,
R. De Nicola, Z. ́Esik, I. Guessarian, W. Kuich, A. Labella, M. Mislove, D. Niwinski.
The papers published here, have been selected among the presented ones after a careful
refereeing by external, anonymous reviewers; I take the occasion to thank them all for
the precious work. The papers of this special issue present new and significant results at
least in two areas. On one hand in the algebraic theory of fixed point operators providing
an equational theory that allows to find the minimal solution for a fixed point equation
in a continuous idempotent semiring and the characterization in the category of sets of
the class of functors that are definable by mu-terms in terms of parity games. On the
other hand, we have a sophisticated example of construction of a categorical semantics
for a language, but also a characterization of categories which provide a general setting
for semantics in computer science with particular respect to fixed point operators
Categories with sums and right distributive tensor product
No full textModels for parallel and concurrent processes lead quite naturally to the study of monoidal categories (Inform. Comput. 88 (2) (1990) 105). In particular a category Tree of trees, equipped with a non-symmetric tensor product, interpreted as a concatenation, seems to be very useful to represent (local) behavior of non-deterministic agents able to communicate (Enriched Categories for Local and Interaction Calculi, Lecture Notes in Computer Science, Vol. 283, Springer, Berlin, 1987, pp. 57-70). The category Tree is also provided with a coproduct (corresponding to choice between behaviors) and the tensor product is only partially distributive w.r.t. it, in order to preserve non-determinism. Such a category can be properly defined as the category of the (finite) symmetric categories on a free monoid, when this free monoid is considered as a 2-category. The monoidal structure is inherited from the concatenation in the monoid. In this paper we prove that for every alphabet A, Tree(A), the category of finite A-labeled trees is equivalent to the free category which is generated by A and enjoys the afore-mentioned properties. The related category Beh(A), corresponding to global behaviors is also proven to be equivalent to the free category which is generated by A and enjoys a smaller set of properties. (C) 2002 Elsevier Science B.V. All rights reserved
Complexes of calcium halides with 1,2-dimethoxyethane (DME)
No full textThe solvento calcium bromide CaBr2(DME) has been prepared by reacting anhydrous calcium acetate with acetyl bromide in dimethoxyethane
(DME), while refluxing a suspension of CaCl2 in DME/SOCl2 gave CaCl2(DME), high yields being secured in both cases.
Crystals of the ionic [CaBr(DME)2(H2O)2]Br (1), were shown to contain heptacoordinated calcium(II) with bidentate DME. Two polymorphs
of the mononuclear, CaBr2(DME)2(MeCOOH) (2), differing for their packing efficiency, have been studied by X-ray diffractometry.
Compound 2 loses one DME and the coordinated acetic acid under vacuum at 30 C, yielding CaBr2(DME). Coordinated DME in
CaX2(DME) was found to be substituted by nitrogen bases in toluene, the adducts CaX2py2 (X = Cl, Br), CaBr2(DMEDA)2,
(DMEDA = N,N0-dimethylethylenediammine) and CaBr2(L–L–L) [L–L–L = 2,6-bis(3,5-dimethyl-N-pyrazolyl)pyridine)] being obtained
in good yields
Transactions and contracts based on reaction systems
No full textSmart contracts are currently en vogue, thanks to the infrastructure provided by the blockchain technology. However, their effective use requires that the textual (legalese) specification of the contract be accompanied by a precise computational definition of the actions leading to its satisfaction or breach, as well as of their admissible sequences. Insofar as contracts can be viewed as prescribing transactional exchanges of well-specified resources among well-specified actors, contract execution can be modelled as following some protocol in a closed world. This suggests a modelling of such executions as interactive processes in reaction systems, where the entities in the background set represent possible allocations of resources to actors and reactions describe changes in such allocations. We use this type of reaction systems and interactive processes as a basis for the modelling of transactions and contracts and explore properties of such processes, highlighting their peculiarities with respect to the original notion of interactive processes in reaction systems. We also discuss several constructions for composition and decomposition of processes, which guarantee equivalence of effects: two interactive processes are equivalent if, starting from the same initial set of allocations, they produce the same final set of allocations. (C) 2021 Elsevier B.V. All rights reserved
PREPARATION AND STRUCTURAL CHARACTERIZATION OF 3 ADAMANTYLCARBOXYLATO DIRUTHENIUM(II,II), DIRUTHENIUM(II,III) AND DIMOLYBDENUM(II,II) COMPOUNDS
No full textThree new compounds containing adamantylcarboxylate ligands, [Ru~(C~~H&O&(CH~OH)~].~CH~OH (l),
[Ru~(C,~,~CO~)~(C~~)(CH~~H)2~CIH. ,OH (2) and Mo,(C,~H,CO,),(C,H,O)~ (3), have been prepared by
reacting K,[Ru2(C0&]-4Hz0, &MO&~, and Moz(OAc), with C&H,,CO,H. Their crystal structures have been
determined. Crystals are as follows. 1: space group P2,/c, a = 12.966(2), b = 16.541(4), c = 12.573(3) A, p= 118.77(2)“,
V= 2364(l) A3, Z = 2, Ru-Ru distance = 2.2809(9) A. 2: space group P2,212,, u = 13.062(l), b = 26.375(4), c = 11.943(2)
A3, Z=4. The Ru-Ru distance is 2.254(8) A. 3: space group Pl, a = 12.897(2), b = 17.308(2),
LY= 107.703(9), p=92.06(1), y=93.01(1)‘, V=2529.0(6) A3, Z=2. The average Mo-MO distance
+he formation of 1 from the starting tetracarbonato complex appears to involve disproportionation
of 2Rud+ to Ru,‘+ and 2Ru3+.
Introductio
The reactivity of the dinuclear halo-bridged cycloplatinated complex [Pt(m-Cl){(k2-P,C)P(OC6H4)(OPh)2}]2 towards neutral ligands
No full textThe reactivity of (cis- þ trans-)[Pt(m-Cl){(k2-P,C)P(OC6H4)(OPh)2}]2 (1) towards several ligands L (L 1⁄4 RCN, P(OMe)3, DMSO, NHEt2, py, CO, C2H4, C8H16) has been studied. Ethylene and 1-octene do not react while the other reactions proceed with cleavage of the halide bridge and formation of one or both geometrical
isomers of [PtCl{(k2-P,C)P(OC6H4)(OPh)2}L] (2e8) depending on the nature of the entering ligand. In some cases equilibrium reactions (L 1⁄4 RCN, DMSO, CO, py) were observed. The structures of [SP4-3]-[PtCl {(k2-P,C)P(OC6H4)(OPh)2}(S)DMSO] ([SP4-3]-4) and [SP4-4]-[[PtCl{(k2-P,C)P(OC6H4)(OPh)2}py] ([SP4-4]-6) are reported
Scrambling of autoinducing precursor peptides investigated by infrared multiphoton dissociation with electrospray ionization and Fourier transform ion cyclotron resonance mass spectrometry
No full textTwo synthetic precursor peptides, H2N-CVGIW and H 2N-LVMCCVGIW, involved in the quorum sensing of Lactobacillus plantarum WCFS1, were characterized by mass spectrometry (MS) with electrospray ionization and 7-T Fourier transform ion cyclotron resonance (ESI-FTICR) instrument. Cell-free bacterial supernatant solutions were analyzed by reversed-phase liquid chromatography with ESI-FTICR MS to verify the occurrence of both pentapeptide and nonapeptide in the bacterial broth. The structural characterization of both protonated peptides was performed by infrared multiphoton dissociation using a continuous CO2 laser source at a wavelength of 10.6 μm. As their fragmentation behavior cannot be directly derived from the primary peptide structure, all anomalous fragments were interpreted as neutral loss of amino acids from the interior of both peptides, i.e., loss of V, G, VG and M, MC, V, CC, from H2N-CVGIW and H 2N-LVMCCVGIW, respectively. Mechanisms of this scrambling are proposed. FTICR MS provides accurate masses of all fragment ions with very low absolute mass errors (<1.6 ppm), which facilitated the reliable assignment of their elemental compositions. The resolving power was more than sufficient to resolve closely isobaric product ions with routine subparts per million mass accuracies. Only the occurrence of pentapeptide was found in the cell-free culture of L. plantarum, grown in Waymouth's medium broth, with a low content of 5.2 ± 2.6 μM by external calibration. Most of it was present as oxidized H2N-CVGIW, that is, the soluble disulfide pentapeptide with a level tenfold higher (i.e., 50 ± 4 μM, n = 3)
The evolution of intellectual capital disclosure driven by European regulatory change. Evidence from the Italian stock market
No full textPurpose - The matter of interest is the reporting and disclosure of intellectual capital (IC) in the global "knowledge economy" era. The aim of the paper is twofold: to verify the level of disclosure of IC through the non-financial statements (NFSs) published by public companies and to identify the main firm-specific factors that explain the propensity to disclose.Design/methodology/approach - Based on the 27 components of IC, a scoring system is designed to measure the level of disclosure of IC by 47 listed Italian companies. Content analysis (CA) is performed on the NFSs these companies published in 2020, to measure each company's so-called intellectual capital disclosure index (ICDI). A regression analysis is then applied to relate the ICDI scores to some firm-specific variables to determine their relevance and influence on the level of disclosure.Findings - Although the NFS was not designed specifically for IC, the results of the analyses show an overall barely satisfactory ability of the NFS to give certain information on IC. Furthermore, the propensity to disclose IC appears significantly related to some firm characteristics considered here, such as capitalization, profitability, productivity, intangibility and financial structure.Research limitations/implications - The analysis relates to a representative but limited sample that does not allow for sectoral or time-series analyses. Extending the companies and years under observation would allow the results to be validated with broader and more in-depth analysis.Originality/value - This paper provides exploratory but interesting evidence about the relationships between IC disclosure (ICD), firm characteristics and market capitalization. Despite several previous studies on the disclosure of IC, no analyses were found that focused on the information capacity of the NFS. Also, to the authors' knowledge, relatively few researchers have considered a set of financial ratios that include capital structure indices
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