Algorithmic Verification of Asynchronous Programs

Asynchronous programming is a ubiquitous systems programming idiom to manage concurrent interactions with the environment. In this style, instead of waiting for time-consuming operations to complete, the programmer makes a non-blocking call to the operation and posts a callback task to a task buffer that is executed later when the time-consuming operation completes. A co-operative scheduler mediates the interaction by picking and executing callback tasks from the task buffer to completion (and these callbacks can post further callbacks to be executed later). Writing correct asynchronous programs is hard because the use of callbacks, while efficient, obscures program control flow. We provide a formal model underlying asynchronous programs and study verification problems for this model. We show that the safety verification problem for finite-data asynchronous programs is expspace-complete. We show that liveness verification for finite-data asynchronous programs is decidable and polynomial-time equivalent to Petri Net reachability. Decidability is not obvious, since even if the data is finite-state, asynchronous programs constitute infinite-state transition systems: both the program stack and the task buffer of pending asynchronous calls can be potentially unbounded. Our main technical construction is a polynomial-time semantics-preserving reduction from asynchronous programs to Petri Nets and conversely. The reduction allows the use of algorithmic techniques on Petri Nets to the verification of asynchronous programs. We also study several extensions to the basic models of asynchronous programs that are inspired by additional capabilities provided by implementations of asynchronous libraries, and classify the decidability and undecidability of verification questions on these extensions.Comment: 46 pages, 9 figure

Covariant Quark Model for the Baryons

A family of simply solvable covariant quark models for the baryons is presented. With optimal parameter choices the models reproduce the empirical spectra of the baryons in all flavor sectors to an accuracy of a few percent. Complete spectra are obtained for all states of the strange, charm and beauty hyperons with $L \leq 2$. The magnetic moments and axial coupling constants of the ground state baryons correspond to those of conventional quark models. We construct current-density operators that are consistent with empirical nucleon form factors at low and medium energies.Comment: 32pages, LateX, 3 figures(postscript

A Post-Succession Analysis of Factors Influencing Coaching Success in NCAA Division I Men’s Basketball – Journal of Issues in Intercollegiate Athletics

Based on the reciprocal determinism component of social learning theory, a total of 736 men’s NCAA Division I basketball coaching changes between 1999 and 2014 were examined to establish which factors were related to conference success following a coaching change. Results from an exploratory latent class analysis indicated that many demographic, environmental, and experiential variables assumed to be important in hiring a new coach are insignificant. However, a program’s previous success, individual coaching ability, and previous coach vacancy circumstance are all significantly related to conference winning differential after a coaching change. Results also indicated a regression to the mean occurs after most coaching changes except for the most elite programs. Pragmatically, however, findings show relatively small increments in winning or losing following a coaching change, suggesting that the impact of a coach is often overstated. Stakeholders can use this information to evaluate coaches, programs, and hiring practices in men’s Division I basketball

Design Features to Accelerate the Higher-Order Assembly of DNA Origami on Membranes

Nanotechnology often exploits DNA origami nanostructures assembled into even larger superstructures up to micrometer sizes with nanometer shape precision. However, large-scale assembly of such structures is very time-consuming. Here, we investigated the efficiency of superstructure assembly on surfaces using indirect cross-linking through low-complexity connector strands binding staple strand extensions, instead of connector strands binding to scaffold loops. Using single-molecule imaging techniques, including fluorescence microscopy and atomic force microscopy, we show that low sequence complexity connector strands allow formation of DNA origami superstructures on lipid membranes, with an order-of-magnitude enhancement in the assembly speed of superstructures. A number of effects, including suppression of DNA hairpin formation, high local effective binding site concentration, and multivalency are proposed to contribute to the acceleration. Thus, the use of low-complexity sequences for DNA origami higher-order assembly offers a very simple but efficient way of improving throughput in DNA origami design.Published as part of The Journal of Physical Chemistry virtual special issue “W. E. Moerner Festschrift”

Curvature in Noncommutative Geometry

Our understanding of the notion of curvature in a noncommutative setting has progressed substantially in the past ten years. This new episode in noncommutative geometry started when a Gauss-Bonnet theorem was proved by Connes and Tretkoff for a curved noncommutative two torus. Ideas from spectral geometry and heat kernel asymptotic expansions suggest a general way of defining local curvature invariants for noncommutative Riemannian type spaces where the metric structure is encoded by a Dirac type operator. To carry explicit computations however one needs quite intriguing new ideas. We give an account of the most recent developments on the notion of curvature in noncommutative geometry in this paper.Comment: 76 pages, 8 figures, final version, one section on open problems added, and references expanded. Appears in "Advances in Noncommutative Geometry - on the occasion of Alain Connes' 70th birthday

Antialactone: A New γ-Lactone from Antiaris africana, and its Absolute Configuration Determined from TDDFT CD Calculations

Four compounds were isolated from the stem bark of Antiaris africana. One of them, a γ-lactone named antialactone (1a), is reported for the first time as a natural product. The structures were determined by comprehensive analyses of their 1D and 2D NMR spectra and EI MS data. The absolute configuration of antialactone acetate (1b) was established by TDDFT CD calculations and comparison with measured CD spectra. The remaining three known compounds were identified, by comparing their spectroscopic data with those reported in the literature, as lichenxanthone, β-sitosterol, and betulinic acid

Taxation of real estate: Russian reforms and foreign practice

In this report, a comparative analysis of Russian reforms in the field of real estate taxation is conducted and foreign practice investigated