191,916 research outputs found
Introduction
No full textThis is a collection of essays in honour of Professor Jyoti K. Parikh. Chapters in this book are written by prominent academics and practitioners who have had a professional connection with Professor Parikh during her long and distinguished career. The book engages with different dimensions of sustainable development and growth and presents a scholarly debate that is relevant to policy and research. The definition of sustainability has evolved considerably. An early definition of sustainable development was presented in the Brundtland Report in 1987, which defined sustainable development as the “development that meets the needs of the present generation without compromising the ability of future generations to meet their own needs”
A toolkit for Parikh matrices
No full textThe Parikh matrix mapping is a concept that provides information on the number of occurrences of certain (scattered) subwords in a word. Although Parikh matrices have been thoroughly studied, many of their basic properties remain open. In the present paper, we describe a toolkit that has been developed to support research in this field. Its functionality includes elementary and advanced operations related to Parikh matrices and the recently introduced variants of P -Parikh matrices and L -Parikh matrices.</p
A toolkit for Parikh matrices
No full textThe Parikh matrix mapping is a concept that provides information on the number of occurrences of certain (scattered) subwords in a word. Although Parikh matrices have been thoroughly studied, many of their basic properties remain open. In the present paper, we describe a toolkit that has been developed to support research in this field. Its functionality includes elementary and advanced operations related to Parikh matrices and the recently introduced variants of P -Parikh matrices and L -Parikh matrices.</p
matthew-p-brown/E_cells_2023: E_cells_2024
No full text<p>This page contains the code used to analyze behavior and voltage imaging data from <strong>Brown et al., 2024</strong>. Further questions can be sent to the corresponding author, Dr. Mark N. Wu ([email protected]).</p>
Counting Problems for Parikh Images
No full textGiven finite-state automata (or context-free grammars) A,B over the same alphabet and a Parikh vector p, we study the complexity of deciding whether the number of words in the language of A with Parikh image p is greater than the number of such words in the language of B. Recently, this problem turned out to be tightly related to the cost problem for weighted Markov chains. We classify the complexity according to whether A and B are deterministic, the size of the alphabet, and the encoding of p (binary or unary)
Dr. Edward P. Wimberly, ITC, July 2011
No full textThis video is a conversation with Dr. Edward P. Wimberly. Dr. Wimberly talks about his book, "No Shame in Wesley's Gospel: A Twenty-First Century Pastoral Gospel". Brad Ost, AUC Woodruff Library, is the interviewer
DESCRIPTIONAL COMPLEXITY AND PARIKH EQUIVALENCE
No full textThe thesis deals with some topics in the theory of formal languages and automata. Specifically, the thesis deals with the theory of context-free languages and the study of their descriptional complexity.
The descriptional complexity of a formal structure (e.g., grammar, model of automata, etc) is the number of symbols needed to write down its description. While this aspect is extensively treated in regular languages, as evidenced by numerous references, in the case of context-free languages few results are known.
An important result in this area is the Parikh’s theorem. The theorem states that for each context-free language there exists a regular language with the same Parikh image. Given an alphabet Σ = {a1, . . . , am}, the Parikh image is a function ψ : Σ^∗→ N^m that associates with each word w∈Σ^∗, the vector ψ(w)=(|w|_a1, |w|_a2, . . . , |w|_am), where |w|_ai is the number of occurrences of ai in w. The Parikh image of a language L⊆Σ^∗ is the set of Parikh images of its words. For instance, the language {a^nb^n | n ≥ 0} has the same Parikh image as (ab)^∗. Roughly speaking, the theorem shows that if the order of the letters in a word is disregarded, retaining only the number of their occurrences, then context-free languages are indistinguishable from regular languages.
Due to the interesting theoretical property of the Parikh’s theorem, the goal of this thesis is to study some aspects of descriptional complexity according to Parikh equivalence. In particular, we investigate the conversion of one-way nondeterministic finite automata and context-free grammars into Parikh equivalent one-way and two-way deterministic finite automata, from a descriptional complexity point of view.
We prove that for each one-way nondeterministic automaton with n states there exist Parikh equivalent one-way and two-way deterministic automata with e^O(sqrt(n lnn)) and p(n) states, respectively, where p(n) is a polynomial. Furthermore, these costs are tight. In contrast, if all the words accepted by the given one-way nondeterministic automaton contain at least two different letters, then a Parikh equivalent one-way deterministic automaton with a polynomial number of states can be found.
Concerning context-free grammars, we prove that for each grammar in Chomsky normal form with h variables there exist Parikh equivalent one-way and two-way deterministic automata with 2^O(h^2 ) and 2^O(h) states, respectively. Even these bounds are tight.
A further investigation is the study under Parikh equivalence of the state complexity of some language operations which preserve regularity. For union, concatenation, Kleene star, complement, intersection, shuffle, and reversal, we obtain a polynomial state complexity over any fixed alphabet, in contrast to the intrinsic exponential state complexity of some of these operations in the classical version. For projection we prove a superpolynomial state complexity, which is lower than the exponential one of the corresponding classical operation. We also prove that for each two one-way deterministic automata A and B it is possible to obtain a one-way deterministic automaton with a polynomial number of states whose accepted language has as Parikh image the intersection of the Parikh images of the languages accepted by A and B
Efficacy of Ultraviolet Light and Antimicrobials to Reduce Listeria monocytogenes in Chill Brines
No full textChill brines used in ready-to-eat meat processing may be an important source of post-processing contamination by Listeria monocytogenes. The purpose of this study was to determine the efficacy of ultraviolet light (UV) in combination with antimicrobials to reduce L. monocytogenes in fresh and used chill brines. Three different antimicrobials were used in combination with UV; citric acid (CA, 0.2 and 0.5%), dimethyl dicarbonate (DMDC, 250 and 500 ppm), and hydrogen peroxide (HP, 2000 and 4000 ppm).
For fresh brine studies, brine (8.0% w/v NaCl) was prepared and inoculated with a cocktail of three L. monocytogenes strains (approximately 6 log CFU/mL). Brine was treated with UV alone, antimicrobials alone, and combination of UV and antimicrobials. Moreover, to observe the effect of treatment temperature and brine circulation through the UV system on survival of listeriae cells, inoculated brine was circulated through the system without any treatment that served as control for all the treatments. For UV treatment, inoculated brine solution was exposed to UV in an Ultraviolet Water Treatment Unit (Model: AMD 150B/1/2T D; Aquionics Inc., Peak output: 254 nm) fitted with an inline chiller to maintain brine temperature of -1°C. Samples were withdrawn at regular intervals for 120 minutes. When L. monocytogenes population was no longer detectable via direct plating on MOX, enrichment was performed and suspect colonies were confirmed using API-Listeria. For antimicrobial-only (i.e., no UV) treatments, a specific concentration of antimicrobial was added in inoculated brine and samples were taken for 120 minutes. For the brine that received combination of UV and antimicrobial treatments, UV was turned on once a specific concentration of antimicrobial was added in inoculated brine and samples were withdrawn at regular intervals for 120 minutes.
When treated with UV alone, L. monocytogenes population decreased from approximately 6 log CFU/mL to below the detection limit (i.e., 1 log CFU/mL) in 15 minutes with the reduction rate of 0.87 log CFU/mL per minute. However, cells were detectable by enrichment through 120 minutes. The highest rate of decline (0.90 log CFU/mL per minute) was achieved by the combination of UV and 500 ppm DMDC (UV+500 ppm DMDC), which was not significantly different from the reduction rates of UV and UV+0.5% CA. UV+500 ppm DMDC reduced L. monocytogenes to the detection limit in 15 minutes and the organism was not detected by enrichment after 60 minutes. Though the reduction rate of UV+0.5% CA was not significantly lower than the rate of UV+500 ppm DMDC (P>0.05), the former treatment resulted in non-detectable levels more quickly (45 minutes) than the latter (60 minutes). Thus, based on enrichment studies UV+0.5% CA was the most effective treatment in reducing the population of L. monocytogenes in fresh brine. Moreover, when brine was treated with 0.5% CA alone the population decreased to below detection limit in 15 minutes with the rate significantly lower than UV+500 ppm DMDC and UV+0.5% CA (P<0.05). However, L. monocytogenes was not detectable by enrichment from 60 minutes. To summarize, through enrichment studies we observed that UV+0.5% CA, UV+500 DMDC, and 0.5% CA Control were more effective than other treatments in reducing the listeriae population to a non-detectable level.
Spent brine is recycled brine that was obtained from a frankfurter processor after its maximum usage. Results of spent brine studies showed that when brine was treated with UV+4000 ppm HP and UV+2000 ppm HP, L. monocytogenes population decreased to the detection limit in 45 minutes and was not detected by enrichment from 120 minutes. These treatments were observed to be the most effective treatments with a reduction rate of 0.12 log CFU/mL per minute. The reduction rate of some other treatments such as, UV+250 and 500 ppm DMDC, UV+0.2% and 0.5% CA, and UV alone was not significantly different from UV+4000 and 2000 ppm HP. However, the population was detected through enrichment up to 120 minutes in all other treatments.
The results of these studies indicate that combinations of UV and antimicrobial may be more effective than either treatment alone (except 0.5% CA treatment) to process fresh chill brines. However, the antimicrobials and UV were less effective for controlling L. monocytgoenes in spent brine; presumably due to the presence of organic matter.Ph. D
Riprap Stability Model Tests
No full textI. Introduction and Background 11. Test Setup and Conditions 111. Presentation of Data IV. Results V. Conclusions Appendices 1. Definition of Terms 2. Photographs of Model Dike Section 3. Model Riprap Stone Analysis 4. Tables of Expected Percent Damage for Armor Stone with Unit WeightsKWP-collectio
Parikh One-Counter Automata
No full textAbstract: Counting abilities in finite automata are traditionally provided by two orthogonal extensions: adding a single counter that can be tested for zeroness at any point, or adding \u2124-valued counters that are tested for equality only at the end of runs. In this paper, finite automata extended with both types of counters are introduced. They are called Parikh One-Counter Automata (POCA): the "Parikh" part referring to the evaluation of counters at the end of runs, and the "One-Counter" part to the single counter that can be tested during runs. Their expressiveness, in the deterministic and nondeterministic variants, is investigated; it is shown in particular that there are deterministic POCA languages that cannot be expressed without nondeterminism in the original models. The natural decision problems are also studied; strikingly, most of them are no harder than in the original models. A parametric version of nonemptiness is also considered
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