9,850 research outputs found
On Asynchronous Session Semantics
This paper studies a behavioural theory of the Ď-calculus with session types under the fundamental principles of the practice of distributed computing â asynchronous communication which is order-preserving inside each connection (session), augmented with asynchronous inspection of events (message arrivals). A new theory of bisimulations is introduced, distinct from either standard
asynchronous or synchronous bisimilarity, accurately capturing the semantic nature of session-based asynchronously communicating processes augmented with
event primitives. The bisimilarity coincides with the reduction-closed barbed congruence. We examine its properties and compare them with existing semantics.
Using the behavioural theory, we verify that the program transformation of multithreaded into event-driven session based processes, using Lauer-Needham duality,
is type and semantic preserving
Field-induced commensurate long-range order in the Haldane-gap system NDMAZ
High-field neutron diffraction studies of the new quantum-disordered S=1
linear-chain antiferromagnet Ni(CHN)N(ClO) (NDMAZ)
are reported. At T=70 mK, at a critical field T applied along the
(013) direction, a phase transition to a commensurate N\'{e}el-like ordered
state is observed. The results are discussed in the context of existing
theories of quantum phase transitions in Haldane-gap antiferromagnets, and in
comparions with previous studies of the related system
Ni(CHN)N(PF)
On Observing Dynamic Prioritised Actions in SOC
We study the impact on observational semantics for SOC of priority mechanisms which combine dynamic priority with local pre-emption. We define manageable notions of strong and weak labelled bisimilarities for COWS, a process calculus for SOC, and provide alternative characterisations in terms of open barbed bisimilarities. These semantics show that COWSâs priority mechanisms partially recover the capability to observe receive actions (that could not be observed in a purely asynchronous setting) and that high priority primitives for termination impose specific conditions on the bisimilarities
Program logics for homogeneous meta-programming.
A meta-program is a program that generates or manipulates another program; in homogeneous meta-programming, a program may generate new parts of, or manipulate, itself. Meta-programming has been used extensively since macros
were introduced to Lisp, yet we have little idea how formally to reason about metaprograms. This paper provides the first program logics for homogeneous metaprogramming
â using a variant of MiniMLe by Davies and Pfenning as underlying meta-programming language.We show the applicability of our approach by reasoning about example meta-programs from the literature. We also demonstrate that our logics are relatively complete in the sense of Cook, enable the inductive derivation of characteristic formulae, and exactly capture the observational properties induced by the operational semantics
An Introduction to Pervasive Interface Automata
Pervasive systems are often context-dependent, component based systems in which components expose interfaces and offer one or more services. These systems may evolve in unpredictable ways, often through component replacement. We present pervasive interface automata as a formalism for modelling components and their composition. Pervasive interface automata are based on the interface automata of Henzinger et al, with several significant differences. We expand their notion of input and output actions to combinations of input, output actions, and callable methods and method calls. Whereas interfaces automata have a refinement relation, we argue the crucial relation in pervasive systems is component replacement, which must include consideration of the services offered by a component and assumptions about the environment. We illustrate pervasive interface autmotata and component replacement with a small case study of a pervasive application for sports predictions
Large-N reduction for N=2 quiver Chern-Simons theories on S^3 and localization in matrix models
We study reduced matrix models obtained by the dimensional reduction of N=2
quiver Chern-Simons theories on S^3 to zero dimension and show that if a
reduced model is expanded around a particular multiple fuzzy sphere background,
it becomes equivalent to the original theory on S^3 in the large-N limit. This
is regarded as a novel large-N reduction on a curved space S^3. We perform the
localization method to the reduced model and compute the free energy and the
vacuum expectation value of a BPS Wilson loop operator. In the large-N limit,
we find an exact agreement between these results and those in the original
theory on S^3.Comment: 46 pages, 11 figures; minor modification
Fluidic Proportional Thruster System Final Report
Fluidic proportional thrust control system with vortex valve
Session-Based Programming for Parallel Algorithms: Expressiveness and Performance
This paper investigates session programming and typing of benchmark examples
to compare productivity, safety and performance with other communications
programming languages. Parallel algorithms are used to examine the above
aspects due to their extensive use of message passing for interaction, and
their increasing prominence in algorithmic research with the rising
availability of hardware resources such as multicore machines and clusters. We
contribute new benchmark results for SJ, an extension of Java for type-safe,
binary session programming, against MPJ Express, a Java messaging system based
on the MPI standard. In conclusion, we observe that (1) despite rich libraries
and functionality, MPI remains a low-level API, and can suffer from commonly
perceived disadvantages of explicit message passing such as deadlocks and
unexpected message types, and (2) the benefits of high-level session
abstraction, which has significant impact on program structure to improve
readability and reliability, and session type-safety can greatly facilitate the
task of communications programming whilst retaining competitive performance
Tuning of antigen sensitivity by T cell receptor-dependent negative feedback controls T cell effector function inflammed tissues
Activated T cells must mediate effector responses sufficient to clear pathogens while avoiding excessive tissue damage. Here we have combined dynamic intravital microscopy with ex vivo assessments of T cell cytokine responses to generate a detailed spatiotemporal picture of CD4+ T cell effector regulation in the skin. In response to antigen, effector T cells arrested transiently on antigen presenting cells, briefly producing cytokine and then resuming migration. Antigen recognition led to PD-1 upregulation of the programmed death-1 (PD-1) glycoprotein by T cells and blocking its canonical ligand, programmed death-ligand 1 (PD-L1), lengthened the duration of migration arrest and cytokine production, showing that PD-1 interaction with PD-L1 is a major negative feedback regulator of antigen responsiveness. We speculate that the immune system employs a mechanism involving T cell recruitment, transient activation, and rapid desensitization, allowing the T cell response to rapidly adjust to changes in antigen presentation and minimize collateral injury to the host
Right-veering diffeomorphisms of compact surfaces with boundary II
We continue our study of the monoid of right-veering diffeomorphisms on a
compact oriented surface with nonempty boundary, introduced in [HKM2]. We
conduct a detailed study of the case when the surface is a punctured torus; in
particular, we exhibit the difference between the monoid of right-veering
diffeomorphisms and the monoid of products of positive Dehn twists, with the
help of the Rademacher function. We then generalize to the braid group B_n on n
strands by relating the signature and the Maslov index. Finally, we discuss the
symplectic fillability in the pseudo-Anosov case by comparing with the work of
Roberts [Ro1,Ro2].Comment: 25 pages, 5 figure
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