Linear Compressed Pattern Matching for Polynomial Rewriting (Extended Abstract)

This paper is an extended abstract of an analysis of term rewriting where the terms in the rewrite rules as well as the term to be rewritten are compressed by a singleton tree grammar (STG). This form of compression is more general than node sharing or representing terms as dags since also partial trees (contexts) can be shared in the compression. In the first part efficient but complex algorithms for detecting applicability of a rewrite rule under STG-compression are constructed and analyzed. The second part applies these results to term rewriting sequences. The main result for submatching is that finding a redex of a left-linear rule can be performed in polynomial time under STG-compression. The main implications for rewriting and (single-position or parallel) rewriting steps are: (i) under STG-compression, n rewriting steps can be performed in nondeterministic polynomial time. (ii) under STG-compression and for left-linear rewrite rules a sequence of n rewriting steps can be performed in polynomial time, and (iii) for compressed rewrite rules where the left hand sides are either DAG-compressed or ground and STG-compressed, and an STG-compressed target term, n rewriting steps can be performed in polynomial time.Comment: In Proceedings TERMGRAPH 2013, arXiv:1302.599

An Environment for Analyzing Space Optimizations in Call-by-Need Functional Languages

We present an implementation of an interpreter LRPi for the call-by-need calculus LRP, based on a variant of Sestoft's abstract machine Mark 1, extended with an eager garbage collector. It is used as a tool for exact space usage analyses as a support for our investigations into space improvements of call-by-need calculi.Comment: In Proceedings WPTE 2016, arXiv:1701.0023

Chromosome segregation impacts on cell growth and division site selection in Corynebacterium glutamicum.

Spatial and temporal regulation of bacterial cell division is imperative for the production of viable offspring. In many rod-shaped bacteria, regulatory systems such as the Min system and nucleoid occlusion ensure the high fidelity of midcell divisome positioning. However, regulation of division site selection in bacteria lacking recognizable Min and nucleoid occlusion remains less well understood. Here, we describe one such rod-shaped organism, Corynebacterium glutamicum, which does not always place the division septum precisely at midcell. Here we now show at single cell level that cell growth and division site selection are spatially and temporally regulated by chromosome segregation. Mutants defective in chromosome segregation have more variable cell growth and aberrant placement of the division site. In these mutants, division septa constrict over and often guillotine the nucleoid, leading to nonviable, DNA-free cells. Our results suggest that chromosome segregation or some nucleoid associated factor influences growth and division site selection in C. glutamicum. Understanding growth and regulation of C. glutamicum cells will also be of importance to develop strains for industrial production of biomolecules, such as amino acids

Equations of State for Warm Dense Carbon from Quantum ESPRESSO

Warm dense plasma is the matter that exists, roughly, in the range of 10,000 to 10,000,000 Kelvin and has solid-like densities, typically between 0.1 and 10 grams per centimeter. Warm dense fluids like hydrogen, helium, and carbon are believed to make up the interiors of many planets, white dwarfs, and other stars in our universe. The existence of warm dense matter (WDM) on Earth, however, is very rare, as it can only be created with high-energy sources like a nuclear explosion. In such an event, theoretical and computational models that accurately predict the response of certain materials are thus very important. Unfortunately, given both the impracticality of producing WDM on Earth and the inherent complexity of the matter itself (partial ionization, non-negligible electron-nuclei interactions, etc.), modeling WDM has proved strenuous and problematic. Despite this difficulty and complexity, advances in Density Functional Theory Molecular Dynamics (DFT-MD) have made such simulations possible. In this thesis, elemental carbon was modeled because of its low atomic number and its relative abundance of experimental data. The Car-Parrinello MD package implemented in the code Quantum ESPRESSO was used to simulate warm dense carbon. Carbon cells were comprised of 24 atoms assigned random positions and were modeled at densities typical of WDM. System temperature was set with the Nosé-Hoover thermostat and by rescaling ionic velocities, and each cell was run at temperatures up to 10,000 Kelvin. Simulation results were plotted, analyzed, and compared to those presented in the literature. Overall, results show pressure divergence that differs substantially with current DFT models of warm dense carbon. This work continues the application of MD simulations to WDM and provides a basis for future research into thermodynamic properties of warm dense plasmas