Recovering purity with comonads and capabilities

© 2020 Owner/Author. In this paper, we take a pervasively effectful (in the style of ML) typed lambda calculus, and show how to extend it to permit capturing pure expressions with types. Our key observation is that, just as the pure simply-typed lambda calculus can be extended to support effects with a monadic type discipline, an impure typed lambda calculus can be extended to support purity with a comonadic type discipline. We establish the correctness of our type system via a simple denotational model, which we call the capability space model. Our model formalises the intuition common to systems programmers that the ability to perform effects should be controlled via access to a permission or capability, and that a program is capability-safe if it performs no effects that it does not have a runtime capability for. We then identify the axiomatic categorical structure that the capability space model validates, and use these axioms to give a categorical semantics for our comonadic type system. We then give an equational theory (substitution and the call-by-value ß and • laws) for the imperative lambda calculus, and show its soundness relative to this semantics. Finally, we give a translation of the pure simply-typed lambda calculus into our comonadic imperative calculus, and show that any two terms which are ß•-equal in the STLC are equal in the equational theory of the comonadic calculus, establishing that pure programs can be mapped in an equation-preserving way into our imperative calculus

Datafun: A Functional Datalog

Datalog may be considered either an unusually powerful query language or a carefully limited logic programming language. Datalog is declarative, expressive, and optimizable, and has been applied successfully in a wide variety of problem domains. However, most use-cases require extending Datalog in an application-specific manner. In this paper we define Datafun, an analogue of Datalog supporting higher-order functional programming. The key idea is to track monotonicity with types

Certain abnormalities in millets induced by X-rays

1. Some of the recessive abnormalities induced by X-rays in E. coracana Gaertn. and Pennisetum typhoides S. & H. are described. 2. In E. coracana are described a chlorophyll deficiency in which the first two or three leaves are green and white banded, but the mature plant is fully green and two mutations effecting the panicle. In P. typhoides have been noted gappiness, tip-sterility, forking and goose-necking in the panicle, male-sterility, and weak-midribbed leaves all behaving as recessives. 3. While some of the plant characters in both these millets mutated easily, others showed no tendency to mutate. Thus in E. coracana the panicle shapes and chlorophyll factors mutated while the grain colour, length of glume and growth factors did not give any mutations, while in P. typhoides the greatest number of mutations were observed in the chlorophyll and panicle characters. 4. P.typhoides threw out more mutations than E. coracana and this is adduced to the diploidy of the former and the tetraploidy of the latter

Knowledge management practices in automotive safety attribute development

Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2006.Includes bibliographical references (p. 100-102).Organizations strive continuously to become efficient. Over the years many of them have tried to attain this through streamlining or reengineering their product development practices. 'While some of them succeed others are less successful. Product development organizations within automotive enterprises are not different in this regard. Most reengineering efforts seem to concentrate on tasks and schedule. Detailed schedules are cascaded while the identification of enablers on delivering to the new schedule is left to individual teams in the organization. At the working level, the reengineering process is misunderstood as abandonment of things gone right from past practices. This sometimes results in teams reinventing solutions to similar problems from the past. The purpose of this thesis is to demonstrate that a key enabler for success in any reengineering effort is to understand existing knowledge management practices and reuse them in the context of proposed changes. To do so, existing practices would have to be captured in usable formats. Proposed changes to existing product development process within an automotive product development organization are studied.(cont.) Comparisons are made between existing and proposed product development process. To focus this comparison and understand the changes better, the development tasks undertaken by a safety attribute team within the product development group is studied in detail. An analysis of the development process undertaken by the safety team to existing schedule is performed through case studies. Based on this analysis scenarios are developed for the proposed changes. From the case studies it is apparent that formalized knowledge management practices in formats usable by development teams will help in reducing iteration time through cascade of robust targets. Recommendations are made to build upon and sustain recently implemented knowledge management practices within the safety attribute team. An implementation roadmap for the new knowledge management frame work is provided.Ram N. Krishnaswami.S.M

The JAK inhibitor tofacitinib suppresses synovial JAK1-STAT signalling in rheumatoid arthritis.

ObjectiveTofacitinib is an oral Janus kinase (JAK) inhibitor for the treatment of rheumatoid arthritis (RA). The pathways affected by tofacitinib and the effects on gene expression in situ are unknown. Therefore, tofacitinib effects on synovial pathobiology were investigated.MethodsA randomised, double-blind, phase II serial synovial biopsy study (A3921073; NCT00976599) in patients with RA with an inadequate methotrexate response. Patients on background methotrexate received tofacitinib 10 mg twice daily or placebo for 28 days. Synovial biopsies were performed on Days -7 and 28 and analysed by immunoassay or quantitative PCR. Clinical response was determined by disease activity score and European League Against Rheumatism (EULAR) response on Day 28 in A3921073, and at Month 3 in a long-term extension study (A3921024; NCT00413699).ResultsTofacitinib exposure led to EULAR moderate to good responses (11/14 patients), while placebo was ineffective (1/14 patients) on Day 28. Tofacitinib treatment significantly reduced synovial mRNA expression of matrix metalloproteinase (MMP)-1 and MMP-3 (p<0.05) and chemokines CCL2, CXCL10 and CXCL13 (p<0.05). No overall changes were observed in synovial inflammation score or the presence of T cells, B cells or macrophages. Changes in synovial phosphorylation of signal transducer and activator of transcription 1 (STAT1) and STAT3 strongly correlated with 4-month clinical responses (p<0.002). Tofacitinib significantly decreased plasma CXCL10 (p<0.005) at Day 28 compared with placebo.ConclusionsTofacitinib reduces metalloproteinase and interferon-regulated gene expression in rheumatoid synovium, and clinical improvement correlates with reductions in STAT1 and STAT3 phosphorylation. JAK1-mediated interferon and interleukin-6 signalling likely play a key role in the synovial response.Trial registration numberNCT00976599

Classification of Subjects as Slow or Rapid Inactivators of Isoniazid Based on the Ratio of Acetylisoniazid to Isoniazid in Urine Determined by a Simple Colorimetric Method

A method for classifying subjects as slow or rapid inactivators of isoniazid based on the ratio of acetylisoniazid to isoniazid in a 3-4 hour urine collection following an intramuscular dose of isoniazid 3 mg./kg. body-weight has been described. Isoniazid and acetylisoniazid have been estimated using methods requiring the use of only a photoelectric colorimeter. Of the 279 patients investigated, 169 (61 per cent) were classified as slow inactivators and 110 (39 per cent) as rapid inactivators. This classification is an excellent agreement (97 per cent) with that based on a standard spectrophotometric method

A note on the breeding of sugarcane varieties resistant to mosaic

The behaviour of certain Coimbatore sugarcane varieties with reference to the mosaic disease has been discussed, showing that those containingSaccharum spontaneum blood are generally resistant or at least tolerant. Preliminary data regarding the supposed correlation between bristles and mosaic resistance have been presented, which indicate that at least in certain cases there appears to be no positive correlation between the high number of bristles and disease resistance, nor in the protection supposed to be afforded by the bristles to the stomata

Dating of the oldest continental sediments from the Himalayan foreland basin

A detailed knowledge of Himalayan development is important for our wider understanding of several global processes, ranging from models of plateau uplift to changes in oceanic chemistry and climate(1-4). Continental sediments 55 Myr old found in a foreland basin in Pakistan(5) are, by more than 20 Myr, the oldest deposits thought to have been eroded from the Himalayan metamorphic mountain belt. This constraint on when erosion began has influenced models of the timing and diachrony of the India-Eurasia collision(6-8), timing and mechanisms of exhumation(9,10) and uplift(11), as well as our general understanding of foreland basin dynamics(12). But the depositional age of these basin sediments was based on biostratigraphy from four intercalated marl units(5). Here we present dates of 257 detrital grains of white mica from this succession, using the Ar-40-(39) Ar method, and find that the largest concentration of ages are at 36-40 Myr. These dates are incompatible with the biostratigraphy unless the mineral ages have been reset, a possibility that we reject on the basis of a number of lines of evidence. A more detailed mapping of this formation suggests that the marl units are structurally intercalated with the continental sediments and accordingly that biostratigraphy cannot be used to date the clastic succession. The oldest continental foreland basin sediments containing metamorphic detritus eroded from the Himalaya orogeny therefore seem to be at least 15-20 Myr younger than previously believed, and models based on the older age must be re-evaluated

Practical API Protocol Checking with Access Permissions

Reusable APIs often define usage protocols. We previously developed a sound modular type system that checks compliance with typestate-based protocols while affording a great deal of aliasing flexibility. We also developed Plural, a prototype tool that embodies our approach as an automated static analysis and includes several extensions we found useful in practice. This paper evaluates our approach along the following dimensions: (1) We report on experience in specifying relevant usage rules for a large Java standard API with our approach. We also specify several other Java APIs and identify recurring patterns. (2) We summarize two case studies in verifying third-party open-source code bases with few false positives using our tool. We discuss how tool shortcomings can be addressed either with code refactorings or extensions to the tool itself. These results indicate that our approach can be used to specify and enforce real API protocols in practice