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It is proved that any $$B_{\pi }^R$$ -matrix has positive determinant. For $${\pi >0}$$ , norm bounds for the inverses of $$B_{\pi }^R$$ -matrices and error bounds for linear complementarity problems associated with $$B_{\pi }^R$$ -matrices are provided. In this last case, the bounds are simpler than previous bounds and also have the advantage that they can be used without previously knowing whether we have a $$B_{\pi }^R$$ -matrix. Some numerical examples show that these new bounds can be considerably sharper than previous ones.

In this paper an accurate method to construct the bidiagonal factorization of collocation and Wronskian matrices of Jacobi polynomials is obtained and used to compute with high relative accuracy their eigenvalues, singular values and inverses. The particular cases of collocation and Wronskian matrices of Legendre polynomials, Gegenbauer polynomials, Chebyshev polynomials of the first and second kind and rational Jacobi polynomials are considered. Numerical examples are included. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

There is a worldwide growing use of chemicals by our developed, industrialized, and technological society. More than 100,000 chemical substances are thus commonly used both by industry and households. Depending on the amount produced, physical-chemical properties, and mode of use, many of them may reach the environment and, notably, the aquatic receiving systems. This may result in undesirable and harmful side-effects on both the human and the ecosystem's health. Mediterranean rivers are largely different from Northern and Central European rivers in terms of hydrological regime, climate conditions (e.g. air temperature, solar irradiation, precipitation), and socio-economics (e.g. land use, tourism, crop types, etc.), with all these factors leading to differences in the relative importance of the environmental stressors, in the classes and levels of the pollutants found and their environmental fate. Furthermore, water scarcity might be critical in affecting water pollution because of the lowered dilution capacity of chemicals. This work provides raw chemical data from different families of microcontaminants identified in three selected Mediterranean rivers (the Sava, Evrotas, and Adige) collected during two sampling campaigns conducted in 2014 and 2015 in three different matrices, namely, water, sediments, and biota (fish). More than 200 organic micropollutants were analyzed, including relevant groups like pharmaceuticals, personal care products, perfluorinated compounds, pesticides, pyrethroid insecticides, flame retardants, and persistent organic pollutants. Data obtained were summarized with some basic statistics for all compound families and matrices analyzed. Observed occurrence and spatial patterns were interpreted both in terms of compound physical-chemical properties and local environmental pressures. Finally, their spatial distribution was examined and their ecotoxicological risk in the water phase was assessed. This allowed locating, at each basin, the most polluted sites (“hot spots”) and identifying the respective river basin specific pollutants (RBSPs), prioritizing them in terms of the potential ecotoxicological risk posed to the aquatic ecosystems., This work has been supported by the European Communities EU 7th Framework Programme Funding under Grant agreement no. 603629-ENV-2013-6.2.1-Globaqua and partly by the Generalitat de Catalunya (Consolidate Research Group 2017-SGR-01404) and by the Spanish Ministry of Science, Innovation and Universities (Projects CEX2018-000794-S and IBERAQUA-NET RED2018-102737-T). Special thanks are due to all partners of the GLOBAQUA consortium and the peer review panel for ensuring quality results and a fruitful collaboration within the frame of the project.

In this paper we provide algorithms for computing the bidiagonal decomposition of the Wronskian matrices of the monomial basis of polynomials and of the basis of exponential polynomials. It is also shown that these algorithms can be used to perform accurately some algebraic computations with these Wronskian matrices, such as the calculation of their inverses, their eigenvalues or their singular values and the solutions of some linear systems. Numerical experiments illustrate the results.

3D porous scaffolds based on agarose and nanocrystalline apatite, two structural components that act as a temporary mineralized extracellular matrix, were prepared by the GELPOR3D method. This shaping technology allows the introduction of thermally-labile molecules within the scaffolds during the fabrication procedure. An angiogenic protein, Vascular Endothelial Growth Factor, and an antibiotic, cephalexin, loaded in mesoporous silica nanoparticles, were included to design multifunctional scaffolds for bone reconstruction. The dual release of both molecules showed a pro-angiogenic behaviour in chicken embryos grown ex ovo, while, at the same time providing an antibiotic local concentration capable of inhibiting Staphylococcus aureus bacterial growth. In this sense, different release patterns, monitored by UV-spectroscopy, could be tailored as a function of the cephalexin loading strategy. The scaffold surface was characterized by a high hydrophilicity, as determined by contact angle measurements, that facilitated the adhesion and proliferation of preosteoblastic cells., Comment: 29 pages, 10 figures

In order to increase the bone forming ability of MBG-PCL composite scaffold, microporosity was created in the struts of 3D-printed MBG-PCL scaffolds for the manufacturing of a construct with a multiscale porosity consisting of meso-, micro- and macro-pores. 3D-printing imparted macroporosity while the microporosity was created by porogen removal from the struts, and the MBG particles were responsible for the mesoporosity. The scaffolds were 3D-printed using a mixture of PCL, MBG and phosphate buffered saline (PBS) particles, subsequently leached out. Microporous-PCL (pPCL) as a negative control, microporous MBG-PCL (pMBG-PCL) and non-microporous-MBG-PCL (MBG-PCL) were investigated. Scanning electron microscopy, mercury intrusion porosimetry and micro-computed tomography demonstrated that the PBS removal resulted in the formation of micropores inside the struts with porosity of around 30% for both pPCL and pMBG-PCL, with both constructs displaying an overall porosity of 80-90%. In contrast, the MBG-PCL group had a microporosity of 6% and an overall porosity of 70%. Early mineralisation was found in the pMBG-PCL post-leaching out and this resulted in the formation a more homogeneous calcium phosphate layer when using a biomimetic mineralisation assay. Mechanical properties ranged from 5 to 25 MPa for microporous and non-microporous specimens, hence microporosity was the determining factor affecting compressive properties. MC3T3-E1 metabolic activity was increased in the pMBG-PCL along with an increased production of RUNX2. Therefore, the microporosity within a 3D-printed bioceramic composite construct may result in additional physical and biological benefits., 34 pages, 10 figures

In this paper, properties and algorithms of q-B&eacute, zier curves and surfaces are analyzed. It is proven that the only q-B&eacute, zier and rational q-B&eacute, zier curves satisfying the boundary tangent property are the B&eacute, zier and rational B&eacute, zier curves, respectively. Evaluation algorithms formed by steps in barycentric form for rational q-B&eacute, zier curves and surfaces are provided.

La educación media superior (EMS) en México es ahora considerada parte de la educación obligatoria en el país. Ante esta obligatoriedad el desarrollar una educación que tenga un mayor impacto en el entorno tanto productivo como educativo cobra una mayor importancia. El aprendizaje basado en proyectos y casos prácticos ha demostrado ser una forma de generar un aprendizaje significativo, aunque desarrollarlo con los escasos recursos que se tienen en las instituciones públicas en el país representa un enorme reto. Por otra parte, está comprobado que las habilidades ligadas al enfoque de las ciencias integradas, a saber: ciencia, tecnología, ingeniería y matemática (STEM, por sus siglas en inglés), son muy importantes en la integración de un aprendizaje más activo y con mejor comprensión de los contenidos científicos. En la EMS en México existen el modelo tradicional de educación, la formación técnica y el modelo dual (ahora mediante el modelo mexicano de formación dual); sin embargo, a pesar de que son buenos esfuerzos, están más enfocados en la educación tradicional, en la capacitación técnica o en la resolución de problemas para adquirir experiencia que en desarrollar una habilidad de “ingenio” para la resolución de problemas prácticos pero no enfocados necesariamente al trabajo en una empresa en particular; habilidad que les permita tener facilidad para resolver problemas y enfrentarse mejor a compromisos como hacer frente al estudio de una ingeniería y posteriormente a diferentes tareas de investigación aplicada. Así, pues, tomando como base el programa Project Lead The Way (PLTW), que se desarrolló en Estados Unidos, el Colegio de Estudios Científicos y Tecnológicos de Querétaro (Cecyteq) desarrolló un programa denominado Bases de Ingeniería, el cual busca desarrollar en los estudiantes de EMS habilidades que les permitan enfrentarse con mayor éxito ya sea tanto a los estudios universitarios de ingeniería como al desarrollo de actividades profesionales en su especialidad técnica en el campo laboral. Este artículo muestra el seguimiento a la eficiencia del programa y la satisfacción que este ha provocado en los estudiantes. Lo anterior con la finalidad de entender cómo aplicar programas especiales que permitan formar talento competitivo a pesar de no contar con un incremento de los recursos materiales disponibles, en un primer comparativo en los planteles Corregidora, Huimilpan, Menchaca, Montenegro, Pedro Escobedo, Querétaro y San Juan del Río.

Almost strictly sign regular matrices are sign regular matrices with a special zero pattern and whose nontrivial minors are nonzero. In this paper we provide several properties of almost strictly sign regular rectangular matrices of maximal rank and analyze their Q R factorization.

We introduce strong B-matrices and strong B-Nekrasov matrices, for which some error bounds for linear complementarity problems are analyzed. In particular, it is proved that the bounds of Garcia-Esnaola and Pena (Appl. Math. Lett. 22, 1071–1075, 2009) and of (Numer. Algor. 72, 435–445, 2016) are asymptotically optimal for strong B-matrices and strong B-Nekrasov matrices, respectively. Other comparisons with a bound of Li and Li (Appl. Math. Lett. 57, 108–113, 2016) are performed.

La tesis central que guia esta editorial es la siguiente: El desarrollo de las competencias comunicativas escriturales y lectoras basadas en la comprensión de lectura, tipologías de textos y escritura creativa requiere de elementos lógicos para el desarrollo de capacidades críticas en los estudiantes universitarios.

It is proved the optimal conditioning for the ∞ -norm of collocation matrices of the tensor product of normalized B-bases among the tensor product of all normalized totally positive bases of the corresponding space of functions. Bounds for the minimal eigenvalue and singular value and illustrative numerical examples are also included.

This paper provides an accurate method to obtain the bidiagonal factorization of many generalized Pascal matrices, which in turn can be used to compute with high relative accuracy the eigenvalues, singular values and inverses of these matrices. Numerical examples are included.

Cycloidal spaces are generated by the trigonometric polynomials of degree one and algebraic polynomials. The critical length of a cycloidal space is the supremum of the lengths of the intervals on which the Hermite interpolation problems are unisolvent. The critical length is related with the critical length for design purposes in computer-aided geometric design. This paper shows an unexpected connection of critical lengths with the zeros of Bessel functions. We prove that the half of the critical length of a cycloidal space is the first positive zero of a Bessel function of the first kind.

In this paper, L D U factorization of nonsingular sign regular and almost strictly sign regular matrices is analyzed. Besides, nonsingular almost strictly sign regular matrices are characterized through the Q R factorization. Illustrative numerical examples are included.

Cauchy–Vandermonde matrices play a fundamental role in rational interpolation theory and in other fields. When all their corresponding nodes are different and positive and all poles are different and negative and follow adequate orderings, these matrices are totally positive. In this paper we provide fast algorithms for computing bidiagonal factorizations of these matrices and their inverses with high relative accuracy. These algorithms can be used to solve with high relative accuracy other algebraic problems, such as the computation of all singular values, all eigenvalues or the solution of certain linear systems. The error analysis of the algorithm for computing the bidiagonal factorization and the corresponding perturbation theory are also performed.

The combined matrix is a very useful concept for many applications. Almost strictly sign regular (ASSR) matrices form an important structured class of matrices with two possible zero patterns, which are either type-I staircase or type-II staircase. We prove that, under an irreducibility condition, the pattern of zero and nonzero entries of an ASSR matrix is preserved by the corresponding combined matrix. Without the irreducibility condition, it is proved that type-I and type-II staircases are still preserved. Illustrative numerical examples are included.

In order to measure the stability properties of Fourier sums, we introduce a conditioning of a representation of the solution of the least squares problem. We relate the conditioning of the discrete polynomial Fourier sums with the corresponding continuous one. We study the asymptotic growth of the conditioning in terms of the degree n. For Fourier–Legendre sums, it is $$O(n^{3/2})$$ . In the case of Fourier–Chebyshev sums, it is linear in the degree. For Fourier sums with Chebyshev polynomials of the second kind, it is $$O(n^2)$$ .

We present a parametrization of a Nekrasov Z-matrix that allows us to compute its inverse with high relative accuracy. Numerical examples illustrating the accuracy of the method are included.

B-matrices form a subclass of P-matrices for which error bounds for the linear complementarity problem are known. It is proved that a bound involved in such problems is asymptotically optimal. $$B_\pi ^R$$ -matrices form a subclass of P-matrices containing B-matrices. For the $$B_\pi ^R$$ -matrices, error bounds for the linear complementarity problem are obtained. We also include illustrative examples showing the sharpness of these bounds.

For a given totally positive space of continuous functions, we analyze the construction of totally positive bases of the space of antiderivatives. If the functions of the totally positive space have continuous derivatives, normalization properties can be used to describe totally positive bases of the space of derivatives and relate them with properties of the Greville abscissae. Construction of totally positive (TP) bases of the space of antiderivatives.Relationship between normalized TP basis and that of the space of derivatives.Characterization in terms of bases with increasing Greville abscissae.

Summary Schoenmakers–Coffey matrices are correlation matrices with important financial applications. Several characterizations of positive extended Schoenmakers–Coffey matrices are presented. This paper provides an accurate and fast method to obtain the bidiagonal decomposition of the conversion of these matrices, which in turn can be used to compute with high relative accuracy the eigenvalues and inverses of positive extended Schoenmakers–Coffey matrices. Numerical examples are included.

In this paper we revisit the problem of monotonicity preservation of curves and surfaces and we provide some new proofs and open problems. In particular, we prove a new formula for the derivation of rational Bézier curves. We also deal with the rational monotonicity preservation of rational Bézier surfaces and a related conjecture is presented.

The design and implementation of a Matlab object-oriented software library for working with polynomials is presented. The construction and evaluation of polynomials in Bernstein form are motivated and justified. Efficient constructions for the coefficients of a polynomial in Bernstein form when the polynomial is not given with this representation are provided. The presented adaptive evaluation algorithm uses the VS (Volk and Schumaker) algorithm, the de Casteljau algorithm, and a compensated VS algorithm. In addition, we have completed the library with other algorithms to perform other usual operations with polynomials in Bernstein form.

In estimating the largest singular value in the class of matrices equiradial with a given $n$-by-$n$ complex matrix $A$, it was proved that it is attained at one of $n(n-1)$ sparse nonnegative matrices (see C.R.~Johnson, J.M.~Pe{\~n}a and T.~Szulc, Optimal Gersgorin-style estimation of the largest singular value; {\em Electronic Journal of Linear Algebra Algebra Appl.}, 25:48--59, 2011). Next, some circumstances were identified under which the set of possible optimizers of the largest singular value can be further narrowed (see C.R.~Johnson, T.~Szulc and D.~Wojtera-Tyrakowska, Optimal Gersgorin-style estimation of the largest singular value, {\it Electronic Journal of Linear Algebra Algebra Appl.}, 25:48--59, 2011). Here the cardinality of the mentioned set for $n$-by-$n$ matrices is further reduced. It is shown that the largest singular value, in the class of matrices equiradial with a given $n$-by-$n$ complex matrix, is attained at one of $n(n-1)/2$ sparse nonnegative matrices. Finally, an inequality between the spectral radius of a $3$-by-$3$ nonnegative matrix $X$ and the spectral radius of a modification of $X$ is also proposed.

Matrices similar to nonsingular totally positive matrices are analyzed. In the particular case of SBD matrices, new characterizations are presented. For more general classes of matrices, methods to assure accurate computations are analyzed.

Weighted φ-transformed systems include many systems of functions useful in C.A.G.D. It is proved that these systems inherit some geometric properties of a given initial system, such as shape preservation or optimal shape preservation. A general class of important rational bases can be obtained as a particular example of weighted φ-transformed systems. For these bases, evaluation and subdivision algorithms are presented. Some relevant applications are pointed out.

Exponential polynomials as solutions of differential equations with constant coefficients are widely used for approximation purposes. Recently, mixed spaces containing algebraic, trigonometric and exponential functions have been extensively considered for design purposes. The analysis of these spaces leads to constructions that can be reduced to Hermite interpolation problems. In this paper, we focus on spaces generated by algebraic polynomials, hyperbolic sine and hyperbolic cosine. We present classical interpolation formulae, such as Newton and Aitken-Neville formulae and a suggestion of implementation. We explore another technique, expressing the Hermite interpolant in terms of polynomial interpolants and derive practical error bounds for the hyperbolic interpolant.

Resumen [16] El presente trabajo muestra la importancia del uso de las TI’s (Tecnologías de la Información) como herramientas de consulta para los productores en mediana y pequeña escala de agricultura protegida; donde se establece la necesidad de acceder a portales en internet o aplicaciones móviles, que provean de información acerca de precios de mercados, alertas de clima y plagas, centros de investigación, financiamientos, apoyos gubernamentales, proveedores de insumos y de servicios, requisitos de clientes, casos de éxito, etc., y de esta manera puedan tomar decisiones que les permita proyectar sus futuras producciones e incrementar su nivel de competitividad; lo anterior para evitar en lo posible intermediarios y obtener mejores ganancias. Además se podrá observar que invertir en TI’s diseñadas para reunir y proveer información completa, confiable, en tiempo real y de diversas fuentes, aunada a un buen uso de estas; disminuirá la incertidumbre en los pequeños productores de agricultura protegida. Se presentarán diversos portales consultados en Internet, así como aplicaciones móviles y sistemas de mensaje de textos para celulares desarrollados en diferentes países por instancias públicas y privadas; que muestran información de algún eslabón de la cadena de valor agrícola, de interés para los productores. Desafortunadamente esta información se encuentra en diferentes medios y el consultante debe navegar entre éstos lo que implica invertir tiempo en la consulta; además debe tener conocimientos en el uso de estas tecnologías, para que pueda crear una visión completa que le ayude a tomar decisiones de acuerdo a la información obtenida. Abstract [20] This paper shows the importance of Information Technology (IT) as a consulting tool for medium and small scale of protected agriculture’s producers. The need to access Internet portals or mobile applications are established, because these technologies provide information about market prices, climate and plague alerts, research centers, financing, government support, input and output suppliers. services, customer requirements, success stories, etc., in this way they can make decisions that allow them to project their future productions and increase their level of competitiveness; to avoid as much as possible intermediaries and obtain better profits. In addition, investment in IT’s will help to producers, to gather complete, reliable, real-time information from various sources, joined with a good use of these, the uncertainty will decrease in small-scale of protected agriculture’s producers. Several portals consulted on Internet we will present, as well as mobile applications and text message systems for cell phones developed in different countries by public and private institutions; they show information of some link in the agricultural value chain, of interest to producers. Unfortunately, this information we founded in different media and the consultants must navigate between these media, which involves investing time in the consultation; also they must have knowledge in the use of these technologies, so that you can create a complete vision to help you make decisions according to the information obtained.

We consider the problem of updating the SVD when augmenting a “tall thin” matrix, i.e., a rectangular matrix A ∈ R m × n with m ≫ n . Supposing that an SVD of A is already known, and given a matrix B ∈ R m × n ′ , we derive an efficient method to compute and efficiently store the SVD of the augmented matrix [ A B ] ∈ R m × ( n + n ′ ) . This is an important tool for two types of applications: in the context of principal component analysis, the dominant left singular vectors provided by this decomposition form an orthonormal basis for the best linear subspace of a given dimension, while from the right singular vectors one can extract an orthonormal basis of the kernel of the matrix. We also describe two concrete applications of these concepts which motivated the development of our method and to which it is very well adapted.

In this work, we evaluate the tissue response and tolerance to a designed 3D porous scaffold composed of nanocrystalline carbonate-hydroxyapatite and agarose as a preliminary step in bone repair and regeneration. These scaffolds were subcutaneously implanted into rats, which were sacrificed at different times. CD4+, CD8+ and ED1+ cells were evaluated as measurements of inflammatory reaction and tolerance. We observed some inflammatory response early after subcutaneous implantation. The 3D interconnected porosity increased scaffold integration via the formation of granulation tissue and the generation of a fibrous capsule around the scaffold. The capsule is initially formed by collagen which progressively invades the scaffold, creating a network that supports the settlement of connective tissue and generating a compact structure. The timing of the appearance of CD4+ and CD8+ cell populations is in agreement with the resolved inflammatory response. The appearance of macrophage activity evidences a slow and gradual degradation activity. Degradation started with the agarose component of the scaffold, but the nano-apatite was kept intact for up to 30 days. Therefore, this apatite/agarose scaffold showed a high capacity for integration by a connective network that stabilizes the scaffold and results in slow nano-apatite degradation. The fundamental properties of the scaffold would provide mechanical support and facilitate bone mobilization, which is of great importance in the masticatory system or large bones.

Sustained-release vaginal microbicides hold out great hope for the prevention of sexual transmission of HIV from men to women. Tenofovir (TFV) –an antiretroviral drug– sustained-release vaginal compacts combining two release control systems (by drug-loading granules with hydrophobic polymers and incorporating them in a hydrophilic matrix) are proposed in this work as a possible microbicide. The polymers used for the drug granules are Eudragit® RS (ERS), an acrylic derivative, and Zein, a maize protein. The hydrophilic matrix is composed of a mixture of hydroxypropylmethyl cellulose (HPMC) and chitosan (CH). The thermal, microscopic, spectrophotometric and X-ray diffraction analysis showed that the drug was not altered during the granulation process. Studies of TFV release, swelling and ex vivo mucoadhesion were subsequently performed on simulated vaginal fluid. The formulation whereby TFV is granulated using twice its weight in ERS, and then including these granules in a matrix in which the CH predominates over HPMC, allows the sustained release of TFV for 144 h, mucoadhesion to the vaginal mucosa for 150 h and a moderate swelling, making it the most suitable formulation of all those studied. These compacts would therefore offer women protection against the sexual acquisition of HIV.

The Bernstein-Fourier algorithm for the evaluation of polynomial curves is extended for the evaluation of polynomial tensor product surfaces. Under a natural hypothesis, accurate evaluation of Bezier curves and surfaces through several algorithms is discussed. Numerical experiments comparing the accuracy of the corresponding Horner, de Casteljau, VS and Bernstein-Fourier algorithms are presented.

The class of B-Nekrasov matrices is a subclass of P-matrices that contains Nekrasov Z-matrices with positive diagonal entries as well as B-matrices. Error bounds for the linear complementarity problem when the involved matrix is a B-Nekrasov matrix are presented. Numerical examples show the sharpness and applicability of the bounds.

An algorithmic characterization of the nonsingular almost strictly sign regular matrices by Neville elimination is presented.

A real matrix A = ( a i j ) 1 ? i , j , ? n is said to be almost strictly totally negative if it is almost strictly sign regular with signature e = ( - 1 , - 1 , ? , - 1 ) , which is equivalent to the property that all its nontrivial minors are negative. In this paper an algorithmic characterization of nonsingular almost strictly totally negative matrices is presented.

The q-Bernstein--Vandermonde matrices are the collocation matrices of the q-Bernstein basis. This paper provides a method that allows us to compute to high relative accuracy the eigenvalues and singular values of these matrices, as well as their inverses.

El presente artículo expone el desarrollo de un conjunto de sistemas que complementan el colposcopio de luz actínica, ya que permiten la captura y manipulación de imágenes médicas que posteriormente se anexan al expediente clínico electrónico incorporado en el primer sistema, una plataforma web, que cumple con las normas mexicanas de registro electrónico y expedientes clínicos para la salud.El segundo sistema es una aplicación de escritorio que permite la manipulación de las imágenes para una mejor visualización con herramientas como anotaciones, lupa, así como la visualización de múltiples imágenes. Este tipo de sistemas promueve el intercambio de información en salud al gestionar la información proporcionada por el paciente y llevar su registro, facilitando el seguimiento y la atención en clínicas de primer nivel, complementado con un sistema para el almacenamiento y distribución de imágenes médicas.

El cáncer cervicouterino continúa siendo un grave problema de salud en México: entre 95 y 99 % de los casos están asociados al virus del papiloma humano (Tovar-Guzmán, 2008). La detección oportuna de lesiones causadas por este virus es fundamental para la prevención y tratamiento de dicha enfermedad (Aguilar-Pérez, 2003). Una forma rápida de diagnosticar este tipo de enfermedades se puede lograr mediante el uso de técnicas no invasivas; en este sentido, las imágenes médicas representan la opción más viable, sin embargo, algunas de las desventajas de este método son el bajo contraste y la presencia de ruido, por lo que es importante desarrollar herramientas que contribuyan a la visualización y mejoramiento de las imágenes. El objetivo del presente trabajo es mejorar la capacidad diagnóstica de imágenes médicas producto del procedimiento colposcópico mediante el desarrollo de un software para la visualización, procesamiento y almacenamiento de video e imágenes médicas, específicamente para la detección rápida de lesiones en el tracto genital femenino ocasionadas por el virus del papiloma humano. Se implementaron filtros digitales para mejorar la visualización de dichas lesiones, los cuales incluyen filtrado manual y automático de fluorescencia para imágenes y la detección en tiempo real mediante el procesamiento de video.

A real matrix is said Almost Strictly Sign Regular (ASSR) if all its nontrivial minors of the same order have the same strict sign. In this research, nonsingular ASSR matrices are characterized through the Neville elimination (NE). In addition, the algorithm is simplified for two important subclases: almost strictly totally negative (ASTN) matrices and Jacobi (tridiagonals) ASSR matrices.

Hermite interpolation problems on cycloidal spaces are analyzed. Newton and Aitken-Neville formulae are obtained. Numerical examples are included.

Neville elimination is an elimination procedure alternative to Gaussian elimination and very adequate when dealing with some special classes of matrices. In this paper, we present pivoting strategies such that the radii of the Gersgorin circles of the Schur complements through Neville elimination with these pivoting strategies reduce their length and we consider classes of matrices important in many applications. We include illustrative examples comparing the results with those obtained with Gaussian elimination and showing that our hypotheses are necessary.

Jacobi–Stirling numbers of first and second kind and their corresponding associated matrices play an important role in Combinatorics. This paper presents an efficient method that guarantees that the computation of the singular values and the inverses of these matrices can be performed with high relative accuracy. Numerical examples are included.

Some inequalities recently obtained for totally positive matrices are extended to more general classes of matrices. Among these larger classes of matrices, sign consistent, sign regular and matrices with signed bidiagonal decomposition are considered. The class of matrices with a signed bidiagonal decomposition contains the nonsingular totally positive matrices and their inverses.