PTML modeling for peptide discovery: in silico design of non-hemolytic peptides with antihypertensive activity

Molecular Diversity - Hypertension is a medical condition that affects millions of people worldwide. Despite the high efficacy of the current antihypertensive drugs, they are associated with...     

Complete ideals and singularities of space curves

We consider complete ideals supported on finite sequences of infinitely near points, in regular local rings with dimensions greater than two. We study properties of factorizations in Lipman special *-simple complete ideals. We relate it to a type of proximity, linear proximity, of the points, and give conditions in order to have unique factorization. Several examples are presented. Received: 2 February 2000 / in final form: 14 March 2001 / Published online: 18 January 2002     

Acoustic Analysis of Pathological Voices Compressedwith MPEG System

The MPEG-1 Layer 3 compression schema of audio signal, commonly known as mp3, has caused a great impact in recent years as it has reached high compression rates while conserving a high sound quality. Music and speech samples compressed at high bitrates are perceptually indistinguishable from the original samples, but very little was known about how compression acoustically affects the voice signal. A previous work with normal voices showed a high fidelity at high-bitrate compressions both in voice parameters and the amplitude-frequency spectrum. In the present work, dysphonic voices were tested through two studies. In the first study, spectrograms, long-term average spectra (LTAS), and fast Fourier transform (FFT) spectra of compressed and original samples of running speech were compared. In the second study, intensities, formant frequencies, formant bandwidths, and a multidimensional set of voice parameters were tested in a set of sustained phonations. Results showed that compression at high bitrates (96 and 128 kbps) preserved the relevant acoustic properties of the pathological voices. With compressions at lower bitrates, fidelity decreases, introducing some important alterations. Results from both works, Gonzalez and Cervera and this paper, open up the possibility of using MPEG-compression at high bitrates to store or transmit high-quality speech recordings, without altering their acoustic properties.     

Novel acrylic macromonomer with amphiphilic character derived from Triton X‐100: Radical copolymerization with methyl methacrylate and thermal properties

This article explores the synthesis of a novel methacrylic macromonomer with an amphiphilic character derived from poly(ethylene glycol) tert‐octylphenyl ether (MT) and its respective homopolymer. To know their reactivity in radical copolymerization reactions with methyl methacrylate (MMA), a model monomer (MTm) was synthesized to determine the reactivity ratios and compare them with the low molar fractions of copolymers of MT with MMA because they were difficult to isolate. They were r_MTm = 0.97 and r_MMA = 0.95. The compositional diagrams when representing the weight fraction of MT and MTm in the feed and the copolymer suggested that a clear correlation exists between the experimental points of the model monomer MTm and the macromonomer MT ones, suggesting that the length of the side poly(ethylene oxide) chain does not affect the reactivity of the methacrylic double bond in the prepared monomers for this type of polymerization reaction. The reactivity ratios of the copolymers have a tendency for the formation of random or Bernoullian copolymers. The glass‐transition temperatures (T_g's) of the prepared copolymers were determined by differential scanning calorimetry, deviated from the Fox equation, and discussed on the basis of treatments that consider the influence of the monomeric units along the copolymer chains, determining the T_g of the corresponding alternating dyads. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1641–1649, 2003     

Minimal, rigid foliations by curves on ℂℙ n

We prove the existence of minimal and rigid singular holomorphic foliations by curves on the projective space ℂℙ ⁿ for every dimension n≥2 and every degree d≥2. Precisely, we construct a foliation ℱ which is induced by a homogeneous vector field of degree d, has a finite singular set and all the regular leaves are dense in the whole of ℂℙ ⁿ . Moreover, ℱ satisfies many additional properties expected from chaotic dynamics and is rigid in the following sense: if ℱ is conjugate to another holomorphic foliation by a homeomorphism sufficiently close to the identity, then these foliations are also conjugate by a projective transformation. Finally, all these properties are persistent for small perturbations of ℱ.?This is done by considering pseudo-groups generated on the unit ball 𝔹 ⁿ ⊆ℂ ⁿ by small perturbations of elements in Diff(ℂ ⁿ ,0). Under open conditions on the generators, we prove the existence of many pseudo-flows in their closure (for the C ⁰-topology) acting transitively on the ball. Dynamical features as minimality, ergodicity, positive entropy and rigidity may easily be derived from this approach. Finally, some of these pseudo-groups are realized in the transverse dynamics of polynomial vector fields in ℂℙ ⁿ . Received March 7, 2002 / final version received November 26, 2002?Published online February 7, 2003 Most of this work has been carried out during a visit of the first author to IMPA/RJ and a visit of the second author to the University of Lille 1. We would like to thank these institutes for hospitality and express our gratitude to CNPq-Brazil and CNRS-France for the financial support which made these visits possible. We are also indebted to Paulo Sad, Marcel Nicolau and the referee whose comments helped us to improve on the preliminary version. Finally, the second author has partially conducted this research for the Clay Mathematics Institute.     

Hydrophilic and hydrophobic copolymer systems based on acrylic derivatives of pyrrolidone and pyrrolidine

This article deals with the synthesis of hydrophilic methacrylic monomers derived from ethyl pyrrolidone [2‐ethyl‐(2‐pyrrolidone) methacrylate (EPM)] and ethyl pyrrolidine [2‐ethyl‐(2‐pyrrolidine) methacrylate (EPyM)] and their respective homopolymers. For the determination of their reactivity in radical copolymerization reactions, both monomers were copolymerized with methyl methacrylate (MMA), the reactivity ratios being calculated by the application of linear and nonlinear mathematical methods. EPM and MMA had ratios of r_EPM = 1.11 and r_MMA = 0.76, and this indicated that EPM with MMA had a higher reactivity in radical copolymerization processes than vinyl pyrrolidone (VP; r_VP = 0.005 and r_MMA = 4.7). EPyM and MMA had reactivity ratios of r_EPyM = 1.31 and r_MMA = 0.92, and this implied, as for the EPM–MMA copolymers, a tendency to form random or Bernoullian copolymers. The glass‐transition temperatures of the prepared copolymers were determined by differential scanning calorimetry (DSC) and were found to adjust to the Fox equation. Total‐conversion copolymers were prepared, and their behavior in aqueous media was found to be dependent on the copolymer composition. The swelling kinetics of the copolymers followed water transport mechanism case II, which is the most desirable kinetic behavior for a swelling controlled‐release material. Finally, the different states of water in the hydrogels—nonfreezing water, freezing bound water, and unbound freezing water—were determined by DSC and found to be dependent on the hydrophilic and hydrophobic units of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 395–407, 2003     

Assessment of some iterative methods for non-symmetric linear systems arising in computational fluid dynamics

Various tests have been carried out in order to compare the performances of several methods used to solve the non-symmetric linear systems of equations arising from implicit discretizations of CFD problems, namely the scalar advection-diffusion equation and the compressible Euler equations. The iterative schemes under consideration belong to three families of algorithms: relaxation (Jacobi and Gauss-Seidel), gradient and Newton methods. Two gradient methods have been selected: a Krylov subspace iteration method (GMRES) and a non-symmetric extension of the conjugate gradient method (CGS). Finally, a quasi-Newton method has also been considered (Broyden). The aim of this paper is to provide indications of which appears to be the most adequate method according to the particular circumstances as well as to discuss the implementation aspects of each scheme.     

Weak type (1, 1) inequalities of maximal convolution operators

In this paper we study the behavior of the constants which appear in the weak type (1, 1) inequalities for maximal convolution operators by means of discrete methods. One of the first applications of these techniques will give us a very simple proof of the ergodic theorem. We also present partial results in order to investigate the best constant in the weak type (1, 1) inequality for the Hardy-Littlewood centered maximal operator in dimension one. In dimension bigger than one we also obtain some lower bounds for that constant.     

Averaged topological equations for dispersed two-phase flows

A general relationship between the volume fraction and the specific interfacial area for averaged dispersed two-phase flows is proposed. This relationship, expressed as a basic set of two scalar evolution equations and two vectorial non-uniformity state equations, is an analytical result obtained by a systematic approach using the derivatives of some generalized functions and a local volume-averaging technique. The proposed set of equations was expressed for measurable macroscopic parameters of the system and has the same generality as the averaged transport equations of two-phase flows. By combination of the basic set of equations, called the averaged topological equations (ATEs), second-order ATEs for the volume fraction were found. The second-order ATEs were expressed both by a Lagrangian formulation and by a Eulerian formulation. The importance and physical meaning of the ATEs developed in this study were clarified within the framework of the theory of kinematic waves.