Subshifts, MSO Logic, and Collapsing Hierarchies

We use monadic second-order logic to define two-dimensional subshifts, or sets of colorings of the infinite plane. We present a natural family of quantifier alternation hierarchies, and show that they all collapse to the third level. In particular, this solves an open problem of [Jeandel & Theyssier 2013]. The results are in stark contrast with picture languages, where such hierarchies are usually infinite.Comment: 12 pages, 5 figures. To appear in conference proceedings of TCS 2014, published by Springe

C-Terminus Glycans with Critical Functional Role in the Maturation of Secretory Glycoproteins

The N-glycans of membrane glycoproteins are mainly exposed to the extracellular space. Human tyrosinase is a transmembrane glycoprotein with six or seven bulky N-glycans exposed towards the lumen of subcellular organelles. The central active site region of human tyrosinase is modeled here within less than 2.5 Å accuracy starting from Streptomyces castaneoglobisporus tyrosinase. The model accounts for the last five C-terminus glycosylation sites of which four are occupied and indicates that these cluster in two pairs - one in close vicinity to the active site and the other on the opposite side. We have analyzed and compared the roles of all tyrosinase N-glycans during tyrosinase processing with a special focus on the proximal to the active site N-glycans, s6:N337 and s7:N371, versus s3:N161 and s4:N230 which decorate the opposite side of the domain. To this end, we have constructed mutants of human tyrosinase in which its seven N-glycosylation sites were deleted. Ablation of the s6:N337 and s7:N371 sites arrests the post-translational productive folding process resulting in terminally misfolded mutants subjected to degradation through the mannosidase driven ERAD pathway. In contrast, single mutants of the other five N-glycans located either opposite to the active site or into the N-terminus Cys1 extension of tyrosinase are temperature-sensitive mutants and recover enzymatic activity at the permissive temperature of 31°C. Sites s3 and s4 display selective calreticulin binding properties. The C-terminus sites s7 and s6 are critical for the endoplasmic reticulum retention and intracellular disposal. Results herein suggest that individual N-glycan location is critical for the stability, regional folding control and secretion of human tyrosinase and explains some tyrosinase gene missense mutations associated with oculocutaneous albinism type I

Digital clay: deriving digital models from freehand sketches

During the initial stages of design, it is not uncommon to find an architect scribbling furiously with a thick pencil. Later in the design process, however, one might not be surprised to encounter the same individual in front of a computer monitor, manipulating three dimensional models in a series of activities that seem completely divorced from their previous efforts.  Armed with evidence that sketching is an effective design method for creative individuals, we also recognize that modelling and rendering applications are invaluable design development and presentation tools, and we naturally seek a connection between these methodologies. We therefore present Digital Clay, a working prototype of a sketch recognition program that interprets gestural and abstracted projection drawings and constructs appropriate three dimensional digital models

Parametric Freehand Sketches

In this paper we present the 2D parametric freehand sketch component of an experimental prototype called GEGROSS (GEsture & Geometric ReconstructiOn based Sketch System). The module implements a gesture alphabet and a calligraphic interface to manage geometric constraints found in 2D sections, that are later used to perform modeling operations. We use different elements to implement this module. The geometric kernel stores model data. The constraint manager 2D DCM handles restrictions. Finally, we use the CALI library to define gestural interfaces. In this paper we present a strategy for integrating these tools, and a calligraphic interface we developed to provide dimensional controls over freehand sketches. Our system allows users to build simple sketches composed by line segments and arcs, which are automatically tidied and beautified. Proportional and dimensional information over sketched parts is provided by handwriting their corresponding sizes

CIGRO: A Minimal Instruction Set Calligraphic Interface for Sketch-Based Modeling

Abstract. Although CAD systems have evolved considerably in functionality, expressiveness and modeling power over the last decades, their user interfaces are still tied to legacy principles and are not suited to the initial stages of prod-uct development. They exhibit steep learning curves, cumber-some and overly structured dialogues, including hundreds of commands. While much of this functionality may be required by the sheer complexity of the tasks these sys-tems are designed to help, we believe the user interface could benefit from sim-pler paradigms based on sketching and drawing to reduce unneeded complex-ity, especially in the conceptual design phase. In what follows, we present the CIGRO system that provides a reduced instruction set calligraphic interface to create polyhedral objects using an incremental drawing paradigm evocative of paper and pencil drawings. Users draw polylines on an axonometric projection, which are automatically beautified and connected to existing parts of the draw-ing. Such line drawings are then converted to a three-dimensional model through a reconstruction process guided by an axonometric inflation method.

The expressive power of two-variable least fixed-point logics

The present paper gives a classification of the expressive power of two-variable least fixed-point logics. The main results are: 1. The two-variable fragment of monadic least fixed-point logic with parameters is as expressive as full monadic least fixed-point logic (on binary structures). 2. The two-variable fragment of monadic least fixed-point logic without parameters is as expressive as the two-variable fragment of binary least fixed-point logic without parameters. 3. The two-variable fragment of binary least fixed-point logic with parameters is strictly more expressive than the two-variable fragment of monadic least fixed-point logic with parameters (even on finite strings)