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Search Results: 1 - 10 of 681804 matches for " Miguel A. García-Sánchez "
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Mixed integer programming model for optimizing the layout of an ICU vehicle
Javier Alejo, Modoaldo Martín, Miguel Ortega-Mier, álvaro García-Sánchez
BMC Health Services Research , 2009, DOI: 10.1186/1472-6963-9-224
Abstract: The first task was to identify the relevant information to define the characteristics of the new vehicles and, in particular, to obtain a satisfactory interior layout to locate all the necessary materials. This information was gathered from health workers related to ICUs. With that information an optimization model was developed in order to obtain a solution. From the MIP model, a first solution was obtained, consisting of a grid to locate the different materials needed for the ICUs. The outcome from the MIP model was discussed with health workers to tune the solution, and after slightly altering that solution to meet some requirements that had not been included in the mathematical model, the eventual solution was approved by the persons responsible for specifying the characteristics of the new vehicles. According to the opinion stated by the SUMMA 112's medical group responsible for improving the ambulances (the so-called "coaching group"), the outcome was highly satisfactory. Indeed, the final design served as a basis to draw up the requirements of a public tender.As a result from solving the Optimization model, a grid was obtained to locate the different necessary materials for the ICUs. This grid had to be slightly altered to meet some requirements that had not been included in the mathematical model. The results were discussed with the persons responsible for specifying the characteristics of the new vehicles.The outcome was highly satisfactory. Indeed, the final design served as a basis to draw up the requirements of a public tender. The authors advocate this approach to address similar problems within the field of Health Services to improve the efficiency and the effectiveness of the processes involved. Problems such as those in operation rooms or emergency rooms, where the availability of a large amount of material is critical are eligible to be dealt with in a simmilar manner.Health systems rely highly on their emergency subsystems and, in particular, on th
Nylon/Porphyrin/Graphene Oxide Fiber Ternary Composite, Synthesis and Characterization  [PDF]
César García-Pérez, Carmina Menchaca-Campos, Miguel A. García-Sánchez, Elsa Pereyra-Laguna, Ociel Rodríguez-Pérez, Jorge Uruchurtu-Chavarín
Open Journal of Composite Materials (OJCM) , 2017, DOI: 10.4236/ojcm.2017.73009
Abstract: This research was based on the manufacture of new composite materials that offer technological possibilities in the development of new devices with greater efficiency. Electrospinning was used to form nylon 66/-tetra-(para-aminophenyl) porphyrin (H2T(p-NH2)PP)/graphene oxide (GO) composite film. Graphene oxide coatings were obtained from graphite, through mechanical exfoliation followed by calcination and ultrasonic agitation in an oxidant solution. These samples were characterized under SEM, FTIR, Raman spectroscopy, UV-vis and R-X techniques. On the other hand, H2T(p-NH2)PP was synthesized in two steps?process by the Rothemun reaction and the Adler Method and it was integrated within nylon polyamide fibers by direct addition of a hexamethylenediamine/adipoyl chloride reactant mixture. The polymerization of the nylon/H2T(p-NH2)PP species occurs in such a way that it starts or ends on the four peripherals-NH2 groups, connected and located in the same molecular plane of H2T(p-NH2)PP, forming nylon chains at the periphery of the macrocycle. The association of GO with nylon/H2T(p-NH2)PP fibers is performed
Nylon/Graphene Oxide Electrospun Composite Coating
Carmina Menchaca-Campos,César García-Pérez,Iván Casta?eda,Miguel A. García-Sánchez,René Guardián,Jorge Uruchurtu
International Journal of Polymer Science , 2013, DOI: 10.1155/2013/621618
Abstract: Graphite oxide is obtained by treating graphite with strong oxidizers. The bulk material disperses in basic solutions yielding graphene oxide. Starting from exfoliated graphite, different treatments were tested to obtain the best graphite oxide conditions, including calcination for two hours at 700°C and ultrasonic agitation in acidic, basic, or peroxide solutions. Bulk particles floating in the solution were filtered, rinsed, and dried. The graphene oxide obtained was characterized under SEM and FTIR techniques. On the other hand, nylon 6-6 has excellent mechanical resistance due to the mutual attraction of its long chains. To take advantage of the properties of both materials, they were combined as a hybrid material. Electrochemical cells were prepared using porous silica as supporting electrode of the electrospun nylon/graphene oxide films for electrochemical testing. Polarization curves were performed to determine the oxidation/reduction potentials under different acidic, alkaline, and peroxide solutions. The oxidation condition was obtained in KOH and the reduction in H2SO4 solutions. Potentiostatic oxidation and reduction curves were applied to further oxidize carbon species and then reduced them, forming the nylon 6-6/functionalized graphene oxide composite coating. Electrochemical impedance measurements were performed to evaluate the coating electrochemical resistance and compared to the silica or nylon samples. 1. Introduction Graphite oxide is a compound of carbon, oxygen, and hydrogen in variable ratios, commonly obtained by treating graphite with strong oxidizers. Strictly speaking “oxide” is an incorrect but historically established name, since graphite is not a metal. The bulk material disperses in basic solutions yielding monomolecular sheets, known as graphene oxide by analogy to graphene, the single-layer form of graphite [1]. Graphene oxide (GO) sheets have recently attracted substantial interest as a possible intermediate for the manufacture of graphene. It typically preserves the layer structure of the parent graphite, but the layers are buckled and the interlayer spacing is about two times larger (~0.7?nm) than that of graphite. Graphene oxide layers are about ?nm thick [2–6]. The edges of each layer are terminated with carboxyl and carbonyl groups. The detailed structure is still not understood due to the strong disorder and irregular packing of the layers [1]. One of the methods used to separate the layers of graphite consists in an aggressive oxidative processes which functionalize the periphery and some places of the graphene
Effects of the Addition of Ortho- and Para-NH2 Substituted Tetraphenylporphyrins on the Structure of Nylon 66
Luis A. Díaz-Alejo,E. Carmina Menchaca-Campos,J. Uruchurtu Chavarín,R. Sosa-Fonseca,Miguel A. García-Sánchez
International Journal of Polymer Science , 2013, DOI: 10.1155/2013/323854
Abstract: The synthetic tetrapyrrole macrocycles, such as porphyrins (H2P) and phthalocyanines (H2Pc), exhibit interesting physicochemical properties suitable to be used in modern technology. For many applications, those species should be trapped or fixed inside graphite, hydrotalcites, silica, TiO2, or polymers. Methodologies for the optimization of the properties of porphyrins, trapped or fixed inside polymers, have been barely developed. Our research works in the development of methodologies for the optimization of incorporation and display of properties of tetrapyrrole macrocycles inside inorganic, polymeric, or hybrid networks. This paper shows some results about the effect of the spatial disposition of the amine (–NH2) groups attached on the periphery of substituted tetraphenylporphyrins, on the Nylon 66 structure and on the display of the physicochemical properties of the trapped macrocycles. Nylon 66 was synthesized from adipoyl chloride and hexamethylenediamine in presence of tetraphenylporphyrins substituted with –NH2 groups localized at the ortho- or para-positions of the phenyls. Cobalt complexes formation was used to quantify the amount of porphyrins in the polymer fibers. Characterization results show that the spatial position of amine groups of the porphyrins has important structural and textural effect on the Nylon 66 fibers and on the fluorescence of the porphyrins integrated into the fibers. 1. Introduction Porphyrins are tetrapyrrole macrocyclic compounds playing a transcendental role in nature as one of the principal components of molecules such as (i) chlorophyll, (ii) the heme group in blood and cytochromes and (iii) cyanocobalamin (Vitamin B12) [1–3]. Formally, porphyrins are modified or substituted aromatic tetrapyrrole macrocyclic compounds derived from porphin (Figure 1), which consists of four pyrrole rings bonded through methine (=CH) bridges in order to form a planar and highly conjugated macrocycle. In the free bases of porphyrins, the two pyrrolic hydrogens can be substituted by a cation, and the remaining two nitrogens tend to easily coordinate with a metal nucleus as to form a stable metalloporphyrin. Synthetic porphyrinic complexes, involving practically all metallic elements of the periodic table, have been synthesized already [2–4]. The central space of porphyrins can only accommodate ions having an atomic radius smaller than 0.201?nm [2–4]; thus, causing that in the porphyrinic complexes containing the larger ions, the metallic element must be located outside of the molecular plane. Similar to the size of the cation, the
An overview of the computational aspects of nonunique factorization invariants
P. A. García-Sánchez
Mathematics , 2015,
Abstract: We give an overview of the existing algorithms to compute nonunique factorization invariants in finitely generated monoids.
A new approach for the computation of the tame degree
Pedro A. García-Sánchez
Mathematics , 2015,
Abstract: In this paper we present a new procedure to compute the tame degree of an atomic monoid that gives rise to a faster algorithm for full affine semigroups.
Diferencias de género en el VIH/sida
Gaceta Sanitaria , 2004, DOI: 10.1590/S0213-91112004000800007
Abstract: women currently have to face a series of additional risk factors for hiv infection, which place them at a disadvantage compared with men. these factors include economic dependence on their partners, difficulties in gaining access to accurate information on infection, prevention, diagnostic tests and counseling, gender violence, and discrimination. these difficulties are demonstrated by the growing epidemic in women, which illustrates the need to guarantee the legal, institutional, social and economic conditions that would enable action to be taken against these factors of inequality. the present article reviews the biological and social factors that influence susceptibility to infection in men and women, gender differences related to health services attendance and disease, and hiv/aids preventive measures from a gender perspective. the situation in europe and the usa has been taken as a reference, although the article is mainly focused on spain.
Feminismo y fictocriticismo en "Ecce fémina" de Tina Suárez Rojas
Soraya García-Sánchez
Cuadernos Interculturales , 2012,
Abstract: Tina Suárez Rojas es una autora contemporánea de Gran Canaria, Espa a. Su poesía sugiere una variedad de tópicos que se entrelazan con diferentes dicotomías: pasado y presente, tradición y modernidad, y mito y realidad, por ejemplo. El propósito de este artículo es estudiar el poema de Suárez Rojas "Ecce femina" extraído de su libro "Una mujer anda suelta" (1999a, 1999b). En "Ecce femina", Suárez Rojas se inspira en esa mujer singular que no es domesticada y que por ello no sigue las normas. No solo se considerará el feminismo como referencia teórica a los papeles tradicionales de las mujeres en la historia, sino que el término fictocriticismo también se entenderá como una forma feminista que se centra en ficción, crítica y teoría destacando la voz de la mujer en su propio contexto.
On curves with one place at infinity
Abdallah Assi,Pedro A. García-Sánchez
Mathematics , 2014,
Abstract: Let $f$ be a plane curve. We give a procedure based on Abhyankar's approximate roots to detect if it has a single place at infinity, and if so construct its associated $\delta$-sequence, and consequently its value semigroup. Also for fixed genus (equivalently Frobenius number) we construct all $\delta$-sequences generating numerical semigroups with this given genus. For a $\delta$-sequence we present a procedure to construct all curves having this associated sequence. We also study the embeddings of such curves in the plane. In particular, we prove that polynomial curves might not have a unique embedding.
Numerical semigroups and applications
Abdallah Assi,Pedro A. García-Sánchez
Mathematics , 2014,
Abstract: The aim of this manuscript is to give some basic notions related to numerical semigroups, and from these on the one hand describe a classical application to the study of singularities of plane algebraic curves, and on the other, show how numerical semigroups can be used to obtain handy examples of nonunique factorization invariants.
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