Syntheses and photophysical properties of new iminopyrrolyl boron complexes and their application in efficient single-layer non-doped OLEDs prepared by spin coating

Efficient non-doped OLEDs have been achieved using new binuclear tetracoordinate organoboron complexes containing 2-(N-aryl)formiminopyrrolyl ligands.     

Jordanian deformation of the open sℓ(2) Gaudin model

We derive a deformed s?(2) Gaudin model with integrable boundaries. Starting from the Jordanian deformation of the SL(2)-invariant Yang R-matrix and generic solutions of the associated reflection equation and the dual reflection equation, we obtain the corresponding inhomogeneous spin-1/2 XXX chain. The semiclassical expansion of the transfer matrix yields the deformed s?(2) Gaudin Hamiltonians with boundary terms.     

Population dynamics with infinite Leslie matrices: finite time properties

Infinite Leslie matrices, introduced by Demetrius 40 years ago, are mathematical models of age-structured populations defined by a countable infinite number of age classes. This article is concerned with determining solutions of the discrete dynamical system in finite time. We address this problem by appealing to the concept of kneading matrices and kneading determinants. Our analysis is applicable not only to populations models, but also to models of self-reproducing machines and self-reproducing computer programs. The dynamics of these systems can also be described in terms of infinite Leslie matrices.     

Analysis of metabolic pools in broilers chicks

This paper shows the possibility of obtaining new parameters for the mathematical modelling of data on stable isotopes in biological systems and its application in obtaining data on metabolic pools of blood plasma, blood serum, liver and muscle of broilers. This theory states that the modelling of turnover used for studies of isotopic incorporation when the metabolism has a single metabolic pool is feasible by the technique of setting an exponential. However, when the metabolism has more than one metabolic pool, it is necessary to apply the linearization technique, linear regression adjustment and evaluation of the assumptions of regression to obtain the kinetic parameters such as half-life (T_1/2) and isotope exchange rate (k). The application of this technique on carbon-13 data from 100 one-day-old chicks, with the change of diet composed of grains of the photosynthetic cycle of plants from C₄ to C₃, in broilers has enabled the discovery that the liver, blood plasma and blood serum have a single metabolic pool; however, the pectoral muscle has two metabolic pools. For the liver, blood plasma and blood serum, the half-life values were found by the exponential fit being T_1/2?=?1.4 days with the rate of exchange of k?=?0.502, T_1/2?=?2.4 days with k?=?0.293 and T_1/2?=?2.0 days with k?=?0.348, respectively. For the pectoral muscle, after linearization, the half-life values were found for T_1/2(1)?=?1.7 and T_1/2(2)?=?3 days, with exchange rates of k₁?=?0.405 and k₂?=?0.235, representing approximately 66 and 34?%, respectively.     

Investigating the potassium interactions with the palytoxin induced channels in Na+/K+ pump

K(+) has been appointed as the main physiological inhibitor of the palytoxin (PTX) effect on the Na(+)/K(+) pump. This toxin acts opening monovalent cationic channels through the Na(+)/K(+) pump. We investigate, by means of computational modeling, the kinetic mechanisms related with K(+) interacting with the complex PTX-Na(+)/K(+) pump. First, a reaction model, with structure similar to Albers-Post model, describing the functional cycle of the pump, was proposed for describing K(+) interference on the complex PTX-Na(+)/K(+) pump in the presence of intracellular ATP. A mathematic model was derived from the reaction model and it was possible to solve numerically the associated differential equations and to simulate experimental maneuvers about the PTX induced currents in the presence of K(+) in the intra- and extracellular space as well as ATP in the intracellular. After the model adjusting to the experimental data, a Monte Carlo method for sensitivity analysis was used to analyze how each reaction parameter acts during each experimental maneuver involving PTX. For ATP and K(+) concentrations conditions, the simulations suggest that the enzyme substate with ATP bound to its high-affinity sites is the main substate for the PTX binding. The activation rate of the induced current is limited by the K(+) deocclusion from the PTX-Na(+)/K(+) pump complex. The K(+) occlusion in the PTX induced channels in the enzymes with ATP bound to its low-affinity sites is the main mechanism responsible for the reduction of the enzyme affinity to PTX.     

Effect of impurities in the large Au-Au distances in gold nanowires

Experimentally obtained atomically thin gold nanowires have presented exceedingly large Au-Au interatomic distances before they break. Since no theoretical calculations of pure gold nanowires have been able to produce such large distances, we have investigated, through ab initio calculations, how impurities could affect them. We have studied the effect of H, B, C, N, O, and S impurities on the nanowire electronic and structural properties, in particular how they affect the maximum Au-Au bond length. We find that the most likely candidates to explain the distances in the range of 3.6 A and 4.8 A are H and S impurity atoms, respectively.     

Double-beam two-photon optical bistability in a Fabry-Perot cavity with polar molecules

Optical bistability in a micrometre-sized Fabry-Perot cavity, filled with appropriate polar molecules, is analysed after two incident beams (with frequenciesgw ₁ andgw ₂) produce in the system a two-photon resonance at frequencygw ₁ +gw ₂. One-photon resonances at the frequenciesgw ₁ andgw ₂ are discarded. It was not necessary to assume a particular relationship betweengw ₁ andgw ₂, and the single-beam two-photon optical bistability whengw ₁ andgw ₂ are of the same order or equal is emphasized.     

Resolution of the Symmetric Nonnegative Inverse Eigenvalue Problem for Matrices Subordinate to a Bipartite Graph

There is a symmetric nonnegative matrix A, subordinate to a given bipartite graph G on n vertices, with eigenvalues _{12 n} if and only if, ₁ + _n 0, ₂ + _n-10,..., _m + _{n - m + 1}0, _{m + 1}0,..., _{n - m} 0, in which m is the matching numberof G. Other observations are also made about the symmetric nonnegative inverse eigenvalue problem with respect to a graph     

The role of salivary peptides in dental caries

Dental caries is a complex disease, characterized by demineralization of tooth structure. With a protective role, several salivary phosphopeptides appear to be involved in remineralization processes, delaying the loss of tooth structure. In this work we have correlated peptide saliva composition with dental caries susceptibility through the analysis of saliva and hydroxyapatite-adsorbed salivary peptides samples. Saliva samples were obtained from two groups, a caries-free and a cariessusceptible group, and were analysed using HPLC-MS and a sequential extraction with 6 m of guanidine followed by tri fluoroacetate. Data analysis has allowed us to verify a strong correlation between large amounts phosphopeptides (PRP1/3, histatin 1 and statherin), and the absence of dental caries, which reinforces the importance of these peptides in the maintenance of tooth integrity. In addition, in the caries-susceptible group a high number of peptide fragments was observed, suggesting a high proteolytic activity.     

Focused ultrasound versus microwave digestion for the determination of lead in must by electrothermal-atomic absorption spectrometry

The content of metals at the different stages of the winemaking process is of great concern because of legal and wine quality reasons. In the present work, we have developed a new fast procedure for metal extraction from must based on focused ultrasound with HNO3 and H2O2, with which microwave digestion of the must is not necessary. Lead was used as a model element to achieve the optimum combination of reagents in order to achieve total extraction. Results were compared with those obtained after microwave digestion of the samples. In addition, conventional and fast programs in conjunction with different matrix modifiers were studied. The method requires few sample mass (ca 0.5 g) and few reagents in low volume (HNO3 50 microL and H2O2 100 microL). The total sample treatment time is only 60 s.