LIPIcs

Repeated idempotent elements are commonly used to characterise iterable behaviours in abstract models of computation. Therefore, given a monoid M, it is natural to ask how long a sequence of elements of M needs to be to ensure the presence of consecutive idempotent factors. This question is formalised through the notion of the Ramsey function R_M associated to M, obtained by mapping every k ∈ ℕ to the minimal integer R_M(k) such that every word u ∈ M^* of length R_M(k) contains k consecutive non-empty factors that correspond to the same idempotent element of M. In this work, we study the behaviour of the Ramsey function R_M by investigating the regular -length of M, defined as the largest size L(M) of a submonoid of M isomorphic to the set of natural numbers {1,2, …, L(M)} equipped with the max operation. We show that the regular -length of M determines the degree of R_M, by proving that k^L(M) ≤ R_M(k) ≤ (k|M|⁴)^L(M). To allow applications of this result, we provide the value of the regular -length of diverse monoids. In particular, we prove that the full monoid of n × n Boolean matrices, which is used to express transition monoids of non-deterministic automata, has a regular -length of (n²+n+2)/2

Time resolved structural dynamics of butadiyne-linked porphyrin dimers

In this work the timescales and mechanisms associated with the structural dynamics of butadiyne-linked porphyrin dimers are investigated through time resolved narrowband pump / broadband probe transient absorption spectroscopy. Our results confirm previous findings that the broadening is partly due to a distribution of structures with different (dihedral) angular conformations. Comparison of measurements with excitations on the red and blue sides of the Q-band unravel the ground and excited state conformational re-equilibration timescales. Further comparison to a planarized dimer, through addition of a ligand, provide conclusive evidence for the twisting motion performed by the porphyrin dimer in solution

Paths of Bridging the Gap Between Academic and Media Practice: The Professors’ Vision in Media Faculties

The article aims to explore paths for bridging the gap between academic qualification in media faculties, departments, and institutes, and media practice from the point of view of media professors in Jordanian universities. A descriptive approach has been adopted to achieve the articles aim, using a survey questionnaire of 50 practitioners of media institutions, and conducting 15 interviews with professors in media faculties and departments at Jordanian universities. The results indicated a gap between academic qualification and media practice. This gap had been due to the different requirements of the market, and the sufficiency of media institutions in terms of media professionals, besides the absence of criteria for accepting students in media faculties, and the academic plans focusing on theoretical aspects more than practical aspects. The results finally concluded that six paths might bridge the gap between the academic media path and media practice: applying the mechanism for accepting students in media majors, developing curricula and plans to keep pace with the requirements of the digital age and the needs of the labor market, recruiting experienced and competent professors and involving professionals in the teaching process, preparing advanced training programs for students; and developing training centers in media faculties

LIPIcs

A deterministic finite automaton (DFA) is composite if its language L() can be decomposed into an intersection ⋂_{i = 1}^k L(_i) of languages of smaller DFAs. Otherwise, is prime. This notion of primality was introduced by Kupferman and Mosheiff in 2013, and while they proved that we can decide whether a DFA is composite, the precise complexity of this problem is still open, with a doubly-exponential gap between the upper and lower bounds. In this work, we focus on permutation DFAs, i.e., those for which the transition monoid is a group. We provide an NP algorithm to decide whether a permutation DFA is composite, and show that the difficulty of this problem comes from the number of non-accepting states of the instance: we give a fixed-parameter tractable algorithm with the number of rejecting states as the parameter. Moreover, we investigate the class of commutative permutation DFAs. Their structural properties allow us to decide compositionality in NL, and even in LOGSPACE if the alphabet size is fixed. Despite this low complexity, we show that complex behaviors still arise in this class: we provide a family of composite DFAs each requiring polynomially many factors with respect to its size. We also consider the variant of the problem that asks whether a DFA is k-factor composite, that is, decomposable into k smaller DFAs, for some given integer k ∈ ℕ. We show that, for commutative permutation DFAs, restricting the number of factors makes the decision computationally harder, and yields a problem with tight bounds: it is NP-complete. Finally, we show that in general, this problem is in PSPACE, and it is in LOGSPACE for DFAs with a singleton alphabet

LIPIcs

A regular language L of finite words is composite if there are regular languages L₁,L₂,…,L_t such that L = ⋂_{i = 1}^t L_i and the index (number of states in a minimal DFA) of every language L_i is strictly smaller than the index of L. Otherwise, L is prime. Primality of regular languages was introduced and studied in [O. Kupferman and J. Mosheiff, 2015], where the complexity of deciding the primality of the language of a given DFA was left open, with a doubly-exponential gap between the upper and lower bounds. We study primality for unary regular languages, namely regular languages with a singleton alphabet. A unary language corresponds to a subset of ℕ, making the study of unary prime languages closer to that of primality in number theory. We show that the setting of languages is richer. In particular, while every composite number is the product of two smaller numbers, the number t of languages necessary to decompose a composite unary language induces a strict hierarchy. In addition, a primality witness for a unary language L, namely a word that is not in L but is in all products of languages that contain L and have an index smaller than L’s, may be of exponential length. Still, we are able to characterize compositionality by structural properties of a DFA for L, leading to a LogSpace algorithm for primality checking of unary DFAs

Directed Random Markets: Connectivity determines Money

Boltzmann-Gibbs distribution arises as the statistical equilibrium probability distribution of money among the agents of a closed economic system where random and undirected exchanges are allowed. When considering a model with uniform savings in the exchanges, the final distribution is close to the gamma family. In this work, we implement these exchange rules on networks and we find that these stationary probability distributions are robust and they are not affected by the topology of the underlying network. We introduce a new family of interactions: random but directed ones. In this case, it is found the topology to be determinant and the mean money per economic agent is related to the degree of the node representing the agent in the network. The relation between the mean money per economic agent and its degree is shown to be linear.Comment: 14 pages, 6 figure

Protease activity in the medium of larch (Larix spec.) embryogenic suspension cultures and medium-protein stabilization by compatible solutes

The stability of recombinant, secreted protein in the medium of transgenic plant cell cultures heavily determines the resulting protein yield, which is a crucial factor for every production system. In order to gain more knowledge about the feasability of rapidly growing larch (Larix sp.) embrogenic cell cultures as a possible expression system for recombinant proteins, spent cell culture medium was characterized in this study. An accumulation of endogenous proteins could be observed in the medium of larch embrogenic suspension cultures which reached up to 1750 μg per g fresh weight. In contrast, low protease activity accumulated within a typical 14-day culture period in the medium. This activity was up to 20 times lower than the protease activity in two callus-derived suspension cultures of tobacco (genotype R1 and BY-2) which were measured in parallel. To asses the stability of foreign proteins, medium aliquots were spiked with Immunoglobulin G (IgG) and the amount of protein degradation was determined after 23 h of incubation by SDS-PAGE. The loss of IgG was comparable in three different larch genotypes, resulting in a mean loss of 18 % during the incubation time. This loss could remarkably be diminished by the addition of ectoin derivatives, known to be protein-protective „compatible solutes“ of bacterial origin. The most effective one was hydroxyectoin which resulted in a 76 % reduction of the observed IgG degradation. The stabilization of proteins in plant cell culture medium by compatible solutes is shown here for the first time. The possible mechanism of the stabilizing effect is discussed