Extended strings and graphs for simple gene assembly

The simple intramolecular model for gene assembly in ciliates is particularly interesting because it can predict the correct assembly of all available experimental data, although it is not universal. The simple model also has a confluence property that is not shared by the general model. A previous formalization of the simple model through sorting of signed permutations is unsatisfactory because it effectively ignores one operation of the model and thus, it cannot be used to answer questions about parallelism in the model, or about measures of complexity. We propose in this paper a string-based model in which a gene is represented through its sequence of pointers and markers and its assembly is represented as a string rewriting process. We prove that this string-based model is equivalent to the permutation-based model as far as gene assembly is concerned, while it tracks all operations of the simple model. We also consider overlap graphs for these strings and prove the results with respect to the overlap of markers.     

Accepting splicing systems

In this paper, we propose a novel approach to splicing systems, namely we consider them as accepting devices. Two ways of iterating the splicing operation and two variants of accepting splicing system are investigated. Altogether, we obtain four models, which are compared with each other as well as with the generating splicing systems from the computational power point of view. Several decision problems concerning the accepting splicing systems are discussed.     

Volume/surface formulation for analyzing scattering from coatedperiodic strips

A surface/surface formulation was used by Perte et al. (see IEEE Trans. Antennas. Propagat.) to analyze the scattering from periodic planar coated strips. This paper is an extension of that work where a combined volume/surface formulation has been used to solve the same problem. This formulation can be applied to problems which involve an inhomogeneous dielectric medium or/and a thick dielectric which requires the inclusion of the edge currents which were neglected as a simplification. Results obtained using the volume/surface formulation have been compared with the results published in the paper written by Petre et al. which were obtained using a surface/surface formulation     

Space–Time Block Coding for Channels with Intersymbol Interference

Stoica, P., and Lindskog, E., Space–Time Block Coding for Channels with Intersymbol Interference, Digital Signal Processing12 (2002) 616–627The downlink of many wireless communication systems can be a MISO channel. An important problem for a MISO channel is how to code across space and time to obtain the same ML receiver as for the corresponding SIMO channel. For flat fading channels, space–time block coding (STBC) is a recent breakthrough solution to this problem. In Lindskog and Paulraj (in Proceedings of ICC'2000, NewOrleans, LA, June 18–22, 2000), STBC has been generalized to channels with intersymbol interference (ISI) for the case of two transmit antennas and one receive antenna. In this paper we first revisit the generalized STBC scheme of Lindskog and Paulraj and show that it has the same appealing properties as the standard STBC for flat fading channels. Then we go on to present an extension of this scheme to ISI channels with any number of transmit and receive antennas.     

Decentring the Creative Self: How Others Make Creativity Possible in Creative Professional Fields

Since its inception, the psychology of creativity has been concerned primarily with the study of individual creators. In contrast, this research is dedicated to an exploration of (a) who has a significant impact on a creative professional's activity and (b) what the contribution is that others make to creative outcomes. The research included interviews with 60 professionals working in science and creative industries in France. The following categories of others emerged: family and friends, peers and students, clients and funders, critics and gatekeepers, and the general public – and they were related to themes depicting the interaction between these different others and the creator. Findings reveal both similarities and differences across the five domains in terms of the specific contribution of others to the creative process. Social interactions play a key formative, regulatory, motivational and informational role in relation to creative work. From ‘internalized’ to ‘distant’, other people are an integral part of the equation of creativity calling for a de‐centring of the creative self and its re‐centring in a social space of actions and interactions.     

Computing the graph-based parallel complexity of gene assembly

We consider a graph-theoretical formalization of the process of gene assembly in ciliates introduced in Ehrenfeucht et al. (2003) [3], where a gene is modeled as a signed graph. The gene assembly, based on three types of operations only, is then modeled as a graph reduction process (to the empty graph). Motivated by the robustness of the gene assembly process, the notions of parallel reduction and parallel complexity of signed graphs have been considered in Harju et al. (2006) [7]. We describe in this paper an exact algorithm for computing the parallel complexity of a given signed graph and for finding an optimal parallel reduction for it. Checking the parallel applicability of a given set of operations and scanning all possible selections amount to a high computational complexity. We also briefly discuss a faster approximate algorithm that however, cannot guarantee finding the optimal reduction.     

Averaging on Manifolds by Embedding Algorithm

We will propose a new algorithm for finding critical points of cost functions defined on a differential manifold. We will lift the initial cost function to a manifold that can be embedded in a Riemannian manifold (Euclidean space) and will construct a vector field defined on the ambient space whose restriction to the embedded manifold is the gradient vector field of the lifted cost function. The advantage of this method is that it allows us to do computations in Cartesian coordinates instead of using local coordinates and covariant derivatives on the initial manifold. We will exemplify the algorithm in the case of SO(3) averaging problems and will rediscover a few well known results that appear in literature.     

TSP: Mining top-k closed sequential patterns

Sequential pattern mining has been studied extensively in the data mining community. Most previous studies require the specification of a min_support threshold for mining a complete set of sequential patterns satisfying the threshold. However, in practice, it is difficult for users to provide an appropriate min_support threshold. To overcome this difficulty, we propose an alternative mining task: mining top-k frequent closed sequential patterns of length no less than min_, where k is the desired number of closed sequential patterns to be mined and min_ is the minimal length of each pattern. We mine the set of closed patterns because it is a compact representation of the complete set of frequent patterns. An efficient algorithm, called TSP, is developed for mining such patterns without min_support. Starting at (absolute) min_support=1, the algorithm makes use of the length constraint and the properties of top-k closed sequential patterns to perform dynamic support raising and projected database pruning. Our extensive performance study shows that TSP has high performance. In most cases, it outperforms the efficient closed sequential pattern-mining algorithm, CloSpan, even when the latter is running with the best tuned min_support threshold. Thus, we conclude that, for sequential pattern mining, mining top-k frequent closed sequential patterns without min_support is more preferable than the traditional min_support-based mining.     

Phase-modulation scatterometry

Phase-modulation scatterometry is a metrology technique for determining, by means of a phase modulator as a key device, the parameters of gratings. The main source of error to be dealt with are the fluctuations of the phase-modulation amplitude. The grating zeroth-order reflectance modulated by the phase modulator is converted into a signal by the photodetector. The measurables are the direct term and the first two harmonics of the signal. For experimental data fitting, we used the ratio of the harmonics over the direct term because it significantly improves the accuracy. A sensitivity analysis was performed for two samples, one real and one theoretical, to find the measurement configuration that insures optimum determination precision for the grating parameters. For the real sample, comparison of the theoretical predictions for sensitivity with the actual values showed a good agreement. For both samples the sensitivity analysis indicated subnanometric precision for the critical dimension (grating linewidth).