Session Types with Runtime Adaptation: Overview and Examples

In recent work, we have developed a session types discipline for a calculus that features the usual constructs for session establishment and communication, but also two novel constructs that enable communicating processes to be stopped, duplicated, or discarded at runtime. The aim is to understand whether known techniques for the static analysis of structured communications scale up to the challenging context of context-aware, adaptable distributed systems, in which disciplined interaction and runtime adaptation are intertwined concerns. In this short note, we summarize the main features of our session-typed framework with runtime adaptation, and recall its basic correctness properties. We illustrate our framework by means of examples. In particular, we present a session representation of supervision trees, a mechanism for enforcing fault-tolerant applications in the Erlang language.Comment: In Proceedings PLACES 2013, arXiv:1312.221

Stationary axisymmetric solutions of five dimensional gravity

We consider stationary axisymmetric solutions of general relativity that asymptote to five dimensional Minkowski space. It is known that this system has a hidden SL(3,R) symmetry. We identify an SO(2,1) subgroup of this symmetry group that preserves the asymptotic boundary conditions. We show that the action of this subgroup on a static solution generates a one-parameter family of stationary solutions carrying angular momentum. We conjecture that by repeated applications of this procedure one can generate all stationary axisymmetric solutions starting from static ones. As an example, we derive the Myers-Perry black hole starting from the Schwarzschild solution in five dimensions.Comment: 31 pages, LaTeX; references adde

Adaptable processes

We propose the concept of adaptable processes as a way of overcoming the limitations that process calculi have for describing patterns of dynamic process evolution. Such patterns rely on direct ways of controlling the behavior and location of running processes, and so they are at the heart of the adaptation capabilities present in many modern concurrent systems. Adaptable processes have a location and are sensible to actions of dynamic update at runtime; this allows to express a wide range of evolvability patterns for concurrent processes. We introduce a core calculus of adaptable processes and propose two verification problems for them: bounded and eventual adaptation. While the former ensures that the number of consecutive erroneous states that can be traversed during a computation is bound by some given number k, the latter ensures that if the system enters into a state with errors then a state without errors will be eventually reached. We study the (un)decidability of these two problems in several variants of the calculus, which result from considering dynamic and static topologies of adaptable processes as well as different evolvability patterns. Rather than a specification language, our calculus intends to be a basis for investigating the fundamental properties of evolvable processes and for developing richer languages with evolvability capabilities

Persistent COVID and a Return to Sport.

ABSTRACT: Coronavirus disease (COVID) has become a global pandemic that has widely impacted athletes at all levels of competition. For many athletes infected with COVID, the course is mild or asymptomatic, and most athletes are able to return to play in a matter of weeks. However, 10% to 15% of people infected with COVID will go on to have prolonged COVID symptoms that last for weeks to months and impact their ability to function and exercise. Not much is known about why certain people become COVID long-haulers, nor are there any predictive tools to predetermine who may have prolonged symptoms. However, many athletes will suffer from prolonged symptoms that may require further evaluation and may prolong their return to exercise, training, and competition. The purpose of this article is to discuss a framework in which sports medicine and primary care physicians can use to evaluate COVID long-haulers and help them return to sport

RFI mitigation with phase-only adaptive beamforming

Connected radio interferometers are sometimes used in the tied-array mode: signals from antenna elements are coherently added and the sum signal applied to a VLBI backend or pulsar processing machine. Usually there is no computer-controlled amplitude weighting in the existing radio interferometer facilities. Radio frequency interference (RFI) mitigation with phase-only adaptive beamforming is proposed for this mode of observation. Small phase perturbations are introduced in each of the antenna's signal. The values of these perturbations are optimized in such a way that the signal from a radio source of interest is preserved and RFI signals suppressed. An evolutionary programming algorithm is used for this task. Computer simulations, made for both one-dimensional and two-dimensional array set-ups, show considerable suppression of RFI and acceptable changes to the main array beam in the radio source direction.Comment: 7 pages, 11 figure

Incomplete ileocecal bypass for ileal pathology in horses: 21 cases (2012–2019)

Background: Incomplete ileocecal bypass can be performed in cases in which an ileal disfunction is suspected but resection of the diseased ileum is not necessary. Objectives: To describe the clinical findings, the surgical technique, and the outcome of 21 cases of colic with ileal pathologies that underwent an incomplete ileocecal bypass. Methods: Historical, clinical, and surgical features of cases diagnosed with pathologies involving the ileum or the ileocecal valve that underwent ileocecal anastomosis without ileal resection were retrieved. Clinical (heart rate, duration of symptoms, presence of reflux, age, weight at arrival) and surgical (surgical pathology, duration of surgery, type of anastomosis) data were retrieved and analysed. Data on short term survival and postoperative complications (colic, post-operative reflux, incisional infection, fever), length of hospital stay, and long term follow up were also obtained. Results: A total of 21 horses met the criteria; 13 horses had ileal impaction (one with muscular hypertrophy), 5 horses had epiploic foramen entrapment, and 3 horses had a pedunculated lipoma. An incomplete ileocecal bypass was performed with a two-layer hand-sewn side-to-side technique in 19 cases and with a stapled side-to-side technique in 2 cases. Short term survival was 95.2%. At 12-months follow up, all horses but two were alive, and 13 of the 14 sport horses returned to their previous level of activity. Long term survival was 90.47%. Conclusions Incomplete ileocecal bypass may represent a valid surgical technique in case of ileocecal valve disfunction when ileum resection is not necessary; this technique may represent an alternative to extensive manipulation without subsequent recurrence of ileal impaction

AdS(3) holography for non-BPS geometries

By using the approach introduced in arXiv:2107.09677 we construct non-BPS solutions of 6D $(1,0)$ supergravity coupled to two tensor multiplets as a perturbation of AdS$_3\times S^3$. These solutions are both regular and asymptotically AdS$_3\times S^3$, so according to the standard holographic framework they must have a dual CFT interpretation as non-supersymmetric heavy operators of the D1-D5 CFT. We provide quantitative evidence that such heavy CFT operators are bound states of a large number of light BPS operators that are mutually non-BPS.Comment: 36 pages, 2 Mathematica files containing data to reproduce our perturbative expansions, 1 readme file summarising how to use the Mathematica file