Application of the orthogonal functions to spectrophotometric analysis

Summary A rapid spectrophotometric method for the analysis of tablets containing the title compounds without preliminary separation is developed. Thus, pyridoxine is determined by measurement at _max while the six-points quadratic orthogonal polynomial has been used to determine meclozine. The mean percentage recoveries (8 determinations) were found to be 101.71±0.64 and 99.77±0.62% (P=0.05) for meclozine and pyridoxine hydrochlorides, respectively. Neither the Vierordt's nor the absorbance ratio methods gave accurate results as the proposed method. The method was applied successfully to the analysis of market preparations.

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Anwendung der Orthogonalfunktion in der spektralphotometrischen Analyse: Bestimmung von Meclozin und Pyridoxin in Tabletten

Zusammenfassung Es wurde ein Verfahren zur schnellen Bestimmung der beiden Verbindungen ohne Vortrennung ausgearbeitet. Pyridoxin wird durch Messung beim Absorptionsmaximum von 292 nm bestimmt, Meclozin wird mit Hilfe eines quadratischen Sechspunkte-Orthogonalpolynoms berechnet. Die Wiederfindungsrate (8 Bestimmungen) lag bei 101,71±0,64 bzw. 99,77±0,62% (P=0,05). Vergleichsbestimmungen nach der Methode von Vierordt und dem Verfahren der Extinktionsverhältnisse gaben weniger genaue Resultate. Die vorgeschlagene Methode wurde mit gutem Erfolg auf handelsübliche Präparate angewendet.

     

Novel Indices for the Topological Complexity of Molecules

Abstract

The development of molecular complexity measures is reviewed. Two novel sets of indices termed topological complexities are introduced proceeding from the idea that topological complexity increases with the overall connectivity of the molecular graph. The latter is assessed as the connectivity of all connected subgraphs in the molecular graph, including the graph itself. First-order, second-order, third-order, etc., topological complexities ⁱ TC are defined as the sum of the vertex degrees in the connected subgraphs with one, two, three, etc., edges, respectively. Zero-order complexity is also specified for the simplest subgraphs–the graph vertices. The overall topological complexity TC is then defined as the sum of the complexities of all orders. These new indices mirror the increase in complexity with the increase in the number of atoms and, at a constant number of atoms, with the increase in molecular branching and cyclicity. Topological complexities compare favorably to molecular connectivities of Kier and Hall, as demonstrated in detail for the classical QSPR test-the boiling points of alkanes. Related to the wide application of molecular connectivities to QSAR studies, a similar importance of the new indices is anticipated.     

Information theoretic spreading measures of orthogonal functions

We calculate information theoretic spreading measures of orthogonal functions associated with solutions of quantum mechanical isospectral potentials. In particular, Shannon, Renyi and Fisher lengths have been evaluated for potentials isospectral to the linear harmonic oscillator and the symmetric Rosen-Morse potentials. We have also compared the behaviour of different lengths for the orthogonal functions and the associated orthogonal polynomials.     

Evolution of Complexity. Molecular Aspects of Preassembly

An extension of neo-Darwinism, termed preassembly, states that genetic material required for many complex traits, such as echolocation, was present long before emergence of the traits. Assembly of genes and gene segments had occurred over protracted time-periods within large libraries of non-coding genes. Epigenetic factors ultimately promoted transfers from noncoding to coding genes, leading to abrupt formation of the trait via de novo genes. This preassembly model explains many observations that to this present day still puzzle biologists: formation of super-complexity in the absence of multiple fossil precursors, as with bat echolocation and flowering plants; major genetic and physical alterations occurring in just a few thousand years, as with housecat evolution; lack of precursors preceding lush periods of species expansion, as in the Cambrian explosion; and evolution of costly traits that exceed their need during evolutionary times, as with human intelligence. What follows in this paper is a mechanism that is not meant to supplant neo-Darwinism; instead, preassembly aims to supplement current ideas when complexity issues leave them struggling.     

Application of orthogonal functions to spectrophotometric analysis: Determination of nifuroxime and furazolidone in pharmaceutical formulations

Summary The orthogonal function method has been applied to the simultaneous determination of nifuroxime and furazolidone in admixture without the need of preliminary separation. Two procedures are proposed. The first one involves measurement of a suitable solution of the mixture in the range from 309 nm to 359 nm with 10 nm intervals to determine nifuroxime, and in the range from 345 nm to 395 nm with 10 nm intervals to determine furazolidone. The second procedure involves determination of either components through measurement at the previously mentioned wavelength range while the absorbance of the partner component is measured at its _max; correction of interference is carried out using an calculated absorbance ratio. Both methods were successfully applied to the analysis of market preparations and further application for routine analysis is recommended. Recoveries were in general between 97% and 102%.

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Anwendung von Orthogonalfunktionen in der spektral-photometrischen Analyse: Bestimmung von Nifuroxim und Furazolidon in pharmazeutischen Präparaten

Zusammenfassung Durch Anwendung von Orthogonalfunktionen können Nifuroxim und Furazolidon in einem Gemisch nebeneinander ohne vorausgehende Trennung bestimmt werden. Zwei verschiedene Verfahren werden vorgeschlagen. Bei dem einen erfolgen die Messungen für Nifuroxim im Bereich von 309 bis 359 nm in Intervallen von 10 nm und für Furazolidon von 345 bis 395 ebenfalls im 10 nm-Abstand. Beim zweiten Verfahren wird einer der Bestandteile bei den genannten Wellenlängen gemessen, während die Extinktion des anderen Bestandteils beim Absorptions-maximum gemessen wird. Die Korrektur für die Störung erfolgt über das berechnete Extinktionsverhältnis. Beide Verfahren wurden erfolgreich bei Handelsprodukten angewendet und werden für Routinebestimmungen empfohlen. Wiederfindungsraten lagen im allgemeinen zwischen 97 und 102%.

     

Two-dimensional confined hydrogen: An entropy and complexity approach

The position and momentum spreading of the electron distribution of the two-dimensional confined hydrogenic atom, which is a basic prototype of the general multidimensional confined quantum systems, is numerically studied in terms of the confinement radius for the 1s, 2s, 2p, and 3d quantum states by means of the main entropy and complexity information-theoretical measures. First, the Shannon entropy and the Fisher information, as well as the associated uncertainty relations, are computed and discussed. Then, the Fisher-Shannon, lopezruiz-mancini-alvet, and LMC-Rényi complexity measures are examined and mutually compared. We have found that these entropy and complexity quantities reflect the rich properties of the electron confinement extent in the two conjugated spaces.     

Impact of Positional Isomerism on Pathway Complexity in Aqueous Media

Pathway complexity has become an important topic in recent years due to its relevance in the optimization of molecular assembly processes, which typically require precise sample preparation protocols. Alternatively, competing aggregation pathways can be controlled by molecular design, which primarily rely on geometrical changes of the building blocks. However, understanding how to control pathway complexity by molecular design remains elusive and new approaches are needed. Herein, we exploit positional isomerism as a new molecular design strategy for pathway control in aqueous self‐assembly. We compare the self‐assembly of two carboxyl‐functionalized amphiphilic BODIPY dyes that solely differ in the relative position of functional groups. Placement of the carboxyl group at the 2‐position enables efficient pairwise H‐bonding interactions into a single thermodynamic species, whereas meso‐substitution induces pathway complexity due to competing hydrophobic and hydrogen bonding interactions. Our results show the importance of positional engineering for pathway control in aqueous self‐assembly.     

Catalytic uses of helicenes displaying phosphorus functions

This review presents an updated state of art of the catalytic uses of chiral phosphorus compounds characterized by a helical scaffold as the key stereogenic element of their structures. These include both helical scaffolds with appended phosphorus functions and helical scaffolds with embedded phosphorus-containing rings (phosphahelicenes). Catalytic applications of helical phosphines in both transition metal catalysis and organocatalysis are presented.     

Development of Structural Complexity by Liquid‐Crystal Self‐assembly

Since the discovery of the liquid‐crystalline state of matter 125 years ago, this field has developed into a scientific area with many facets. This Review presents recent developments in the molecular design and self‐assembly of liquid crystals. The focus is on new exciting soft‐matter structures distinct from the usually observed nematic, smectic, and columnar phases. These new structures have enhanced complexity, including multicompartment and cellular structures, periodic and quasiperiodic arrays of spheres, and new emergent properties, such as ferroelctricity and spontaneous achiral symmetry‐breaking. Comparisons are made with developments in related fields, such as self‐assembled monolayers, multiblock copolymers, and nanoparticle arrays. Measures of structural complexity used herein are the size of the lattice, the number of distinct compartments, the dimensionality, and the logic depth of the resulting supramolecular structures.     

X-Ray structures of two families of hydrolytic antibodies

The catalytic mechanisms of two esterase-like catalytic antibodies (Abs) have been determined, based on kinetic data and on structures of the complexes with transition-state analogs and with a stable substrate analog of the reactions they catalyze. Both Abs stabilize the oxyanion intermediate close to the transition state in ester hydrolysis. The different geometries of the hydrogen bonds that participate in this stabilization account for most of the difference between the efficiencies of these two Abs.     

Light-controlled smart nanotubes based on the orthogonal assembly of two homopolymers

Two homopolymers can orthogonally self-assemble into pseudo-copolymer based on terminal host-guest interactions, and these supramolecular copolymers further fabricate one-dimensional nanotubes in water. By applying alternate UV/visible light, the aggregates can reversibly assemble and disassemble by means of the association and disassociation of active connection.     

Controlling the assembly of nanoparticle mixtures with two orthogonal polymer complexation reactions

Self-assembly from mixed dispersions of three sizes of monodisperse polystyrene nanoparticles, large (L), medium (M), and small (S), was controlled by coating each particle type with either a monofunctional or bifunctional polymer capable of participating in specific complexation reactions. The complexation reactions were (1) complexation between phenolic polymers and polyethylene glycol (PEG) containing polymers and (2) condensation of phenylboronic acid containing polymers with polyols. These complexation reactions function independently and can be "turned off" independently; phenylboronic acid complexation was reversed by lowering the pH, whereas the interactions of phenolic copolymers with PEG copolymers could be reversed by adding excess PEG homopolymer. The specificity and reversibility of the interactions was demonstrated by the formation of simple binary aggregates from mixtures. The bifunctional copolymers were poly(vinyl phenol-co-diallyldimethyl ammonium chloride), Ph-DADMAC, and poly(3-acrylamide phenylboronic acid-co-PEG methacrylate), PBA-PEG. The monofunctional polymer was polyvinylalcohol, PVA. Ph-DADMAC forms complexes with PBA-PEG (H-bonding) and with anionic surfaces or polymers (electrostatic/polyelectrolyte complexation). PBA-PEG complexes with Ph-DADMAC (H-bonding) and with PVA (boronate ester formation). PVA does not interact with Ph-DADMAC; therefore, PVA coated particles do not deposit onto Ph-DADMAC coated particles.     

Comparison of the force field in various pyrochlore families. II. Phases presenting structural defects

A previous study of various A₂B₂O₆O′ pyrochlore families by vibrational spectroscopy allowed the analysis of the ir and Raman spectra and the force fields of pyrochlore phases presenting structural defects. The spectra of the following compounds were compared: (i) ideal pyrochlore Cd₂Ta₂O₇, (ii) lacunary Tl₂Ta₂O₆, (iii) nonstoichiometric Pb_1.5Ta₂O_6.5, and (iv) Pb_2.3Ta₂O_7.3 exhibiting regular shear planes. If the tridimensional network of TaO₆ octahedra is not modified and the perturbations concern only the A₄O′ tetrahedra network, a slight modification of the vibrational spectra and a weak decrease in the TaO stretching and OTaO bending force constants are observed. But, if the octahedra network is perturbed, large modifications appear on the spectra, revealing unambiguously the existence of new types of bonds created by the defects in the structure. The Raman intense lines observed in the low frequency range in lead compounds is also discussed.     

Emission enhancement using two orthogonal targets in double pulse laser-induced breakdown spectroscopy

The enhancement of emission intensity resulting from the interaction between two laser-induced plasmas on two orthogonal targets was investigated using double pulse laser-induced breakdown spectroscopy (LIBS) at 0.7 Pa, by means of time-resolved spectroscopy and fast photography. The results showed that the interaction between both plasmas improved carbon emission intensity in comparison to a single laser-induced plasma. For all the carbon lines of interest 477.2 nm (CI), 426.7 nm (CII), and 473.4 nm (C₂ Swan band head), the intensity enhancement showed a maximum at a delay between lasers in the range from 2 to 5 μs; moreover it increased with the fluence of the first laser. On the other hand, in the case of C₂ the intensity enhancement reached a maximum at 5 mm from the target; however it decreased with increasing fluence of the second laser. The largest intensity enhancement found was twofold for atomic species and sixfold for molecular species.