Search Results (4)

This paper establishes some links between Sturm–Liouville problems and the well-known controllability property in linear dynamic systems, together with a control law design that allows any prefixed arbitrary final state finite value to be reached via feedback from any given finite initial conditions. The scheduled second-order dynamic systems are equivalent to the stated second-order differential equations, and they are used for analysis purposes. In the first study, a control law is synthesized for a forced time-invariant nominal version of the current time-varying one so that their respective two-point boundary values are coincident. Afterward, the parameter that fixes the set of eigenvalues of the Sturm–Liouville system is replaced by a time-varying parameter that is a control function to be synthesized without performing, in this case, any comparison with a nominal time-invariant version of the system. Such a control law is designed in such a way that, for given arbitrary and finite initial conditions of the differential system, prescribed final conditions along a time interval of finite length are matched by the state trajectory solution. As a result, the solution of the dynamic system, and thus that of its differential equation counterpart, is subject to prefixed two-point boundary values at the initial and at the final time instants of the time interval of finite length under study. Also, some algebraic constraints between the eigenvalues of the Sturm–Liouville system and their evolution operators are formulated later on. Those constraints are based on the fact that the solutions corresponding to each of the eigenvalues match the same two-point boundary values. Full article

This study offers a detailed comparative analysis of the reflexes of Proto-Bantu noun class prefixes within nine Gabonese languages belonging to the B50, B60, and B70 groups of Guthrie’s referential inventory of the Bantu languages. Genealogically speaking, all of them are part of the Kwilu-Ngounie subclade of the Bantu family’s West-Coastal Bantu branch. Starting out from a robust dataset comprising over 4000 lexical items collected through fieldwork and existing descriptions, the Comparative Method is used to distinguish changes in noun class morphology due to regular sound shifts from those emerging from analogical reanalysis and levelling. The comparative study shows a systematic reduction and reorganization of the inherited Proto-Bantu noun class system, notably the loss of classes 12/13 and 19 across all languages, variable retention and loss of classes 7/8 and 11, and complex patterns of reshuffling involving classes 5, 9/10, and 1/2. Key innovations, potentially reinforcing lexicon-based hypotheses of phylogenetic subgrouping within Kwilu-Ngounie, include the development of a class 7 allomorphy conditioned by stem-initial segments in the B50 languages and the emergence of vocalic prefixes restricted to the B60 and B70 languages. Full article

An important set of sound changes affected the South Bantu languages through the impact of front vowels on following consonants, most notably under the form of the class 5 nominal prefix *i-. These consonant changes are well known, but their extent has been underestimated, as the substantial data in this paper show. There is not even a standard name for these changes, which are here called “Preceding-I effects”. This paper offers a detailed study of the relevant conditioning factor, calling attention to the understudied category of hiatus resolution in the history of Bantu languages. Although the reflexes in individual languages vary and levelling often reduced the number of surviving examples, indications of systematic PI-effects in all the subgroups of the South Bantu branch contrast with other Bantu branches and suggest a common conditioning factor was present in Proto-South-Bantu. Full article

In this work, the synthesis, selective chemical modifications, and self-assembly behavior in aqueous media of a novel poly(2-(dimethylamino)ethyl acrylate)₂₀-b-poly(N-isopropylacrylamide)₁₁-b-poly(oligo ethylene glycol methyl ether acrylate)₁₈ (PDMAEA₂₀-b-PNIPAM₁₁-b-POEGA₁₈) dual-responsive (pH and temperature) and triply hydrophilic amino-based triblock terpolymer are reported. The amine functional triblock terpolymer was synthesized by sequential reversible addition fragmentation chain transfer polymerization (RAFT) polymerization and molecularly characterized by size exclusion chromatography (SEC) and ¹H-NMR spectroscopy that evidenced the success of the three-step polymerization scheme. The tertiary amine pendant groups of the PDMAEA block were chemically modified in order to produce the Q₁PDMAEA₂₀-b-PNIPAM₁₁-b-POEGA₁₈ as well as the Q₆PDMAEA₂₀-b-PNIPAM₁₁-b-POEGA₁₈ quaternized triblock terpolymers (Q₁ and Q₆ prefixes show the number of carbon atoms (C1 and C6) attached on the PDMAEA groups) using methyl iodide (CH₃I) and 1-iodohexane (C₆H₁₃I) as the quaternizing agents and the SPDMAEA₂₀-b-PNIPAM₁₁-b-POEGA₁₈ sulfobetainized triblock terpolymer using 1,3 propanesultone (C₃H₆O₃S) as the sulfobetainization agent. The self-assembly properties of the triblock terpolymers in aqueous solutions upon varying temperature and solution pH were studied by light scattering and fluorescence spectroscopy experiments. The novel triblock terpolymers self-assemble into nanosized aggregates upon solution temperature rise above the nominal lower critical solution temperature (LCST) of the temperature-responsive PNIPAM block. The remarkable stimuli-responsive self-assembly behavior of the novel triblock terpolymers in aqueous media make them interesting candidates for biomedical applications in the fields of drug and gene delivery. Full article