Formal communication elimination and sequentialization equivalence proofs for distributed system models

Equivalence reasoning with distributed system models, expressed directly as imperative programs with explicit parallelism, communication operations, storage variables and boolean conditions, remains virtually unexplored. Only reasoning with models expressed as process algebras has been amply dealt with in literature. However, these formalisms do not contemplate either storage variables or Boolean conditions as fundamental items, although these items become essential in most situations. This article develops the foundation of the until now non existent theory of equivalence reasoning with the aforementioned imperative notation and two novel equivalence proof techniques: communication elimination and sequentialization. The development is grounded on state systems and transition interleavings, as treated by Manna and Pnueli. Equivalence proofs safely transform a model via the application of a sequence of equivalence laws; aiming to obtain an equivalent model which is purely sequential, free from internal communication operations and parallelism, as a simplification of the initial model. After this, verification of the original model can be carried out, indirectly, in the simplified model, thus reducing complexity. Some of the presented novel notions are: (1) modular procedure for decomposition of both models and proofs, (2) interface behavior for statement semantics, (3) interface equivalence between behaviors, between statements and between procedures, (4) a set of communication elimination laws and (5) substitution rules of procedure references by their bodies or by references to equivalent procedures. An elimination proof construction algorithm is also presented; when it terminates, deadlock freedom of the original model can be decided. The main design lines of a computer aided equivalence reasoning tool are outlined as well. This is the foundation for a more widely applicable tool. As an illustration, the sequentialization proof of a simplified pipelined processor is overviewed. It is modeled as a distributed system with procedures and two levels of parallelism. The model obtained at the end of the equivalence proof is the sequential loop of a Von Neumann processor. This result establishes that the original model is deadlock-free, behaves as a processor and, as a consequence, the partition of processor functions among parallel processes is correct. The ratio of the upper bounds on the number of states of the final over the initial models, \(\frac{final}{initial}\) , is \(\frac{1}{2^{672}}\) .     

Ultrastructure of spermiogenesis and the spermatozoon of Anoplocephaloides dentata (Cestoda, Cyclophyllidea, Anoplocephalidae), an intestinal parasite of Arvicolidae rodents

Spermiogenesis in Anoplocephaloides dentata begins with the formation of a differentiation zone delimited by a ring of arched membranes. This conical area shows 2 parallel centrioles with associated anterior reduced striated roots but without an intercentriolar body. Only 1 of the centrioles develops an axoneme that grows into a cytoplasmic extension. Two crestlike bodies appear when the nucleus initiates its migration along the spermatid body. We describe for the first time at the end of spermiogenesis the formation of an apical cone before the strangulation of the ring of arched membranes. The mature spermatozoon of A. dentata is filiform, tapered at both ends, and lacks mitochondria. Its anterior extremity has an apical cone measuring about 1,400 x 350 nm and 2 crestlike bodies. Cortical microtubules are spiralled at an angle of about 30 degrees to the spermatozoon axis. The axoneme, of the 9+1 pattern of Trepaxonemata (Polycladida, Seriata, "Typhloplanoida," "Dalyellioida," and Neodermata lacks a periaxonemal sheath and does not reach the extremities of the spermatozoon. Numerous granules of electron-dense material are observed in the posterior regions of each spermatozoon. Analysis of ultrastructural features found during spermiogenesis in A. dentata corroborates the presence of striated roots associated with the centrioles in cyclophyllidean species. Moreover, the presence of striated roots is described for the first time in type IV spermiogenesis.     

Assisting non-expert speakers of under-resourced languages in assigning stems and inflectional paradigms to new word entries of morphological dictionaries

This paper presents a new method with which to assist individuals with no background in linguistics to create monolingual dictionaries such as those used by the morphological analysers of many natural language processing applications. The involvement of non-expert users is especially critical for under-resourced languages which either lack or cannot afford the recruitment of a skilled workforce. Adding a word to a morphological dictionary usually requires identifying its stem along with the inflection paradigm that can be used in order to generate all the word forms of the new entry. Our method works under the assumption that the average speakers of a language can successfully answer the polar question “is x a valid form of the word w to be inserted?”, where x represents tentative alternative (inflected) forms of the new word w. The experiments show that with a small number of polar questions the correct stem and paradigm can be obtained from non-experts with high success rates. We study the impact of different heuristic and probabilistic approaches on the actual number of questions.     

Paramodulation with Well-founded Orderings

For many years, all existing completeness results for Knuth–Bendixcompletion and ordered paramodulation required the term ordering to be well-founded, monotonic and total(izable) on ground terms.Then, it was shown that well-foundedness and the subterm propertywere enough for ensuring completeness of ordered paramodulation.Here we show that the subterm property is not necessary either.By using a new restricted form of rewriting, we obtain a completenessproof of ordered paramodulation for Horn clauses with equality,where well-foundedness of the ordering suffices. Apart fromthe theoretical significance of this result, some potentialapplications motivating the interest of dropping the subtermproperty are given. The proof of the results included in thisarticle, being still technical in some parts, is pretty muchshorter and easier to read than the one we have in the preliminaryversion of this work presented at the CADE, 2002 conference(Bofill, and Rubio, 2002, CADE, Vol. 2392 of LNAI, pp. 456–470).     

Is ionic dialysance useful for early detection of vascular access dysfunction? Six illustrative cases

Continuous ionic dialysance monitoring is a useful clinical tool to determine the dialysis dose in real time in each hemodialysis session. We followed up 49 patients for 16 months. Six patients with a Kt reduction of ≥20% in >3 consecutive hemodialysis sessions were identified. Fistulography demonstrated significant stenosis in all 6 patients. Angioplasty was performed in 5 with an excellent angiographic result and optimal Kt levels were restored. Unexplained and persistent Kt reduction in patients with stable chronic kidney disease under hemodialysis could represent, together with an accurate vascular access examination, a practical and additional indirect method for the early detection of vascular access dysfunction.     

Exploiting parallelism on progressive alignment methods

Multiple Sequence Alignment (MSA) constitutes an extremely powerful tool for important biological applications such as phylogenetic analysis, identification of conserved motifs and domains and structure prediction. In spite of the improvement in speed and accuracy introduced by MSA programs, the computational requirements for large-scale alignments requires high-performance computing and parallel applications. In this paper we present an improvement to a parallel implementation of T-Coffee, a widely used MSA package. Our approximation resolves the bottleneck of the progressive alignment stage on MSA. This is achieved by increasing the degree of parallelism by balancing the guide tree that drives the progressive alignment process. The experimental results show improvements in execution time of over 68% while maintaining the biological accuracy.     

Assessing the Recyclability of Supramolecularly Assembled Organocatalytic Species: A Theoretical Insight

Asymmetric organocatalytic synthesis is a powerful tool in organic chemistry to achieve desired stereoisomers in high purity via mild catalytic routes. The immobilization of homogeneous catalytic species onto heterogeneous phases embodies the evolution of asymmetric catalysis, since it allows the recycling of the catalyst for several runs until degradation. Previously reported non-covalent immobilization of proline-based catalysts for aldol reaction onto magnetic nanoparticles functionalized with β-cyclodextrin (MNP-β-CB) demonstrated the viability of the methodology. This paper proposes two new catalyst recycling strategies based on Cucurbit[7]uril (CB[7]) for the aldol reaction and the Robinson annulation. These recycling methodologies are conceptually different. The former relies on the homogeneous encapsulation of the catalyst in cucurbituril, CB[7] ⋅ Cat, and its recycling in the aqueous phase by extraction of the aldol product with organic solvents. The latter relies on the heterogeneous encapsulation of the catalyst as MNP-CB[7] ⋅ Cat2 system and its recycling by magnetic harvesting. Density functional theory (DFT) calculations have been employed to rationalize the thermodynamics of experimental results, and to suggest caveats and plausible improvements in view of a future catalytic design.     

Urban spatial structure,agglomeration economies,and economic growth in Barcelona: An intra‐metropolitan perspective*

This paper presents an intra‐metropolitan approach to analyse the impact of urban spatial structure on local economic growth. Focusing on the Barcelona metropolitan region (BMR) between 1986 and 2001, we estimate a municipal employment growth model in which dynamic agglomeration economies related to urban spatial structure are considered using distance to employment centres, to assess metropolitan effects, and distance‐weighted variables, to measure neighbourhood effects. The results obtained show the existence of neighbourhood specialization economies and metropolitan urbanization‐localization economies fostering local growth. All of this leads to the paper's main conclusion: urban spatial structure is important for economic growth in an intra‐metropolitan context.     

Proline‐Derived Aminotriazole Ligands: Preparation and Use in the Ruthenium‐Catalyzed Asymmetric Transfer Hydrogenation

The preparation of 2‐triazolyl‐ and 2‐triazolylmethylpyrrolidines from L ‐proline and L ‐trans‐4‐hydroxyproline is described, along with their evaluation as chiral ligands in ruthenium‐catalyzed asymmetric transfer hydrogenation. Modular evolution of the ligands by introduction of remote substituents is also presented, showing a surprisingly important effect on the performance of the ligands.     

Role of dense shelf water cascading in the transfer of organochlorine compounds to open marine waters

Settling particles were collected by an array of sediment trap moorings deployed along the Cap de Creus (CCC) and Lacaze-Duthiers (LDC) submarine canyons and on the adjacent southern open slope (SOS) between October 2005 and October 2006. This array collected particles during common settling processes and particles transferred to deep waters by dense shelf water cascading (DSWC). Polychlorobiphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), chlorobenzenes (CBzs)--pentachlorobenzene and hexachlorobenzene--and hexachlorocyclohexanes were analyzed in all samples. The results show much higher settling fluxes of these compounds during DSWC than during common sedimentation processes. The area of highest deposition was located between 1000 and 1500 m depth and extended along the canyons and outside them showing their channelling effects but also overflows of dense shelf water from these canyons. Higher fluxes were observed near the bottom (30 m above bottom; mab) than at intermediate waters (500 mab) which is consistent with the formation and sinking of dense water close to the continental shelf and main displacement through the slope by the bottom. DSWC involved the highest settling fluxes of these compounds ever described in marine continental slopes and pelagic areas, e.g., peak values of PCBs (960 ng · m(-2) · d(-1)), DDTs (2900 ng · m(-2) · d(-1)), CBzs (340 ng · m(-2) · d(-1)) and lindane (180 ng · m(-2) · d(-1)).