Andrzej Ehrenfeucht

Circularity and other invariants of gene assembly in ciliates (2009)

Ehrenfeucht, Andrzej, Petre, Ion, Prescott, David M., Rozenberg, Grzegorz

Ciliates (an ancient group of single cell organisms) have two sorts of nuclei with different functionalities: the micronucleus and the macronucleus. After the cell mating the micronuclear genes are...

Characterizing the micronuclear gene patterns in ciliates (2009)

Ehrenfeucht, Andrzej, Harju, Tero, Petre, Ion, Rozenberg, Grzegorz

The process of gene assembly in ciliates is one of the most complex examples of DNA processing known in any organism, and it is fascinating from the computational point of view - it is a prime...

Transitivity of Local Complementation and Switching on Graphs (2009)

Ehrenfeucht, Andrzej, Harju, Tero, Rozenberg, Grzegorz

The operations complementation C, local complementation lx and switching sx for the vertices x of a finite undirected graph are considered. The operation lx complements the subgraph induced by the...

Computation in Living Cell: Gene Assembly in Ciliates (2009)

Ehrenfeucht, Andrzej, Harju, Tero, Petre, Ion, Prescot, David M., Rozenberg, Grzegorz

Natural Computing is concerned with computation that is taking place in Nature. The investigation of computations in living cells is one of the central and fastest growing areas of research in this...

Under consideration for publication in Math. Struct. in Comp. Science String and graph reduction systems for gene assembly in ciliates (2008)

Andrzej Ehrenfeucht, Ion Petre, David M. Prescott, Grzegorz Rozenberg

Ciliates have developed a unique nuclear dualism- two nuclei of di erent functionality: the germline micronucleus and the somatic macronucleus. The way that ciliates assemble the macronuclear genes...

Leslie Valiant (2008)

Andrzej Ehrenfeucht, Michael Kearns, David Haussler

We prove alower bound of ( 1 ln 1 + VCdim(C) ) on the number of random examples required for distribution-free learning of a concept class C, where VCdim(C) is the Vapnik-Chervonenkis dimension and...

Math with Calculators in Elementary Schools (2007)

Patricia Baggett Andrzej, Andrzej Ehrenfeucht

Hand-held calculators allow the introduction of significant changes in the content and methods of teaching mathematics in elementary grades. Children can learn the arithmetic of real numbers from the...

Conceptual i zing Conceptualizing in Assembly Tasks (2007)

Patricia Bagett, Andrzej Ehrenfeucht

This paper gives a method to determine a person's hypothetical conceptualization of an object-- its breakdown into subassemblies, subsubassemblies, and so on-- from the person's sequence of...

THE EMBEDDING PROBLEM FOR SWITCHING CLASSES (2005)

Andrzej Ehrenfeucht, Jurriaan Hage, Tero Harju, Grzegorz Rozenberg

1 In the context of graph transformation we look at the operation of switching, which can be viewed as an elegant method for realizing global transformations of (group-labelled) graphs through local...

Finite Metrics in Switching Classes (2004)

Ehrenfeucht, Andrzej, Harju, Tero, Rozenberg, Grzegorz

Let D be a finite set together with a real valued function g with g(x,x)=0 and g(x,y) = g(y,x). A switch of g is obtained by transforming g using a local valuation s: gs (x,y) = s(x) + g(x,y) + s(y)...

Embedding Linear Orders in Grids (2004)

Ehrenfeucht, Andrzej, Harju, Tero, Rozenberg, Grzegorz

A grid is a two-dimensional permutation: an m×n-grid of size mn is an m×n-matrix where the entries run through the elements {1,2, ... , mn}. We prove that if d1 and d2 are any two linear...

Zebra Factorizations in Free Semigroups (2004)

Ehrenfeucht, Andrzej, Harju, Tero, Rozenberg, Grzegorz

Let S be a semigroup of words over an alphabet A. Let W(S) consist of those elements w of S for which every prefix and suffix of w belongs to S. We show that W(S) is a free semigroup. Moreover, S is...

Embedding in switching classes with skew gains (2004)

Andrzej Ehrenfeucht, Jurriaan Hage, Tero Harju

Abstract. In the context of graph transformation we look at the operation of switching, which can be viewed as an elegant method for realizing global transformations of (group-labelled) graphs...

How an Unfamiliar Thing Should Be Called (2002)

Baggett, Patricia, Ehrenfeucht, Andrzej

An empirical method is described to derive good names for unfamiliar objects. Three principles were used in deriving the names: (1) The vocabulary and structure of the names should be within the...

Encoding and Retaining Information in the Visuals and Verbals of an Educational Movie (2002)

Baggett, Patricia, Ehrenfeucht, Andrzej

Viewers watching a narrated movie are simultaneously presented information in two media, visual and verbal/auditory. This study shows there is no competition for resources in an educational movie:...

A Framework for Forming, Modifying, and Using Multimedia Concepts in Memory. Part I. Mathematical Formulation. (2002)

Baggett,Patricia, Ehrenfeucht,Andrzej

A theoretical framework for the structures and processes of memory is presented. The model is based on three main notions: memory, concepts, and processors. Part I puts forth the notions in...

The Size of k-pseudotrees (1992)

Emanuel Knill, Andrzej Ehrenfeucht, David Haussler, Mailstop K

Let X be a finite set. A k-pseudotree on X is a family F of subsets of X such that: (i) X 2 F and for every x 2 X, fxg 2 F ; (ii) for every U 2 F there exists an x 2 U such that if V 2 F and x 2 V ,...

Building physical and mental models in assembly tasks (1991)

Baggett, Patricia, Ehrenfeucht, Andrzej

Two videotapes were designed which showed how to assemble an 80-piece object, a lift. The lift had a hierarchical structure (breakdown into subassemblies, subsubassemblies, etc.), which was used as...

The Computational Complexity of (XOR, AND)-Counting Problems (1990)

Andrzej Ehrenfeucht, Marek Karpinski

We characterize the computational complexity of counting the exact number of satisfying assignments in (XOR; AND)-formulas in their RSE-representation (i.e., equivalently, polynomials in GF [2][x 1 ;...

Use of the 'Perceptron' algorithm to distinguish translational initiation sites in E. coli (1982)

Stormo, Gary D., Schneider, Thomas D., Gold, Larry, Ehrenfeucht, Andrzej

We have used a “Perceptron” algorithm to find a weighting function which distinguishes E. coli translational initiation sites from all other sites in a library of over 78,000 nucleotides of mRNA...

Organization of Memory

Ehrenfeucht, Andrzej, Mycielski, Jan

A new learning algorithm is presented that may have applications in the theory of natural and artificial intelligence.

Organization of Memory

Ehrenfeucht, Andrzej, Mycielski, Jan

A new learning algorithm is presented that may have applications in the theory of natural and artificial intelligence.