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Search Results: 1 - 10 of 216468 matches for " Jorge Uruchurtu-Chavarín "
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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
Recurrence Quantification Analysis of Rough Surfaces Applied to Optical and Speckle Profiles  [PDF]
Oscar Sarmiento Martinez, Darwin Mayorga Cruz, Jorge Uruchurtu Chavarín, Estela Sarmiento Bustos
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.44083
Abstract: In this paper, Recurrence Quantification Analysis (RQA) is set as a practical nonlinear data tool to establish and compare surface roughness (Ra) through percentage parameters of a dynamical system: Recurrence (%REC), Determinism (%DET) and Laminarity (%LAM). Variations in surface roughness of different machining procedures from a typical metallic casting comparator are obtained from scattering intensity of a laser beam and expressed as changes in the statistics of speckle patterns and profiles optical properties. The application of the analysis (RQA) by Recurrence Plots (RPs), allowed to distinguish between machining procedures, highlighting features that other methods are unable to detect.
Caracterización de la agresividad atmosférica sobre los materiales metálicos estructurales en la Zona Metropolitana de la Ciudad de México
Ramón Mu?oz Ledo,Jorge Uruchurtu Chavarín
Revista internacional de contaminación ambiental , 2002,
Abstract:
Valvuloplastía mitral percutánea
ángeles-Valdés, Josué;Uruchurtu Chavarín, Eduardo;
Archivos de cardiología de México , 2005,
Abstract: pure mitral stenosis has a bad prognosis due to progressive narrowing of the mitral orifice, which requires surgical techniques to widen it. among these procedures are open heart surgery and the percutaneous approach through balloon valvuloplasty. this article is an update of the indications and on the use of echocardiography for patient selection. it describes transeptal puncture and analyses the advantages and disadvantages of the different interventional techniques with: one balloon, emphasizing on a technique modified by us, i.e., th use of nucleus balloon; with inoue balloon, double balloon technique, and cribier's valvulotomy, which is not performed in our country because no valvulotome is currently available. we analyze the success rate, which is of 100% when considering any increase in valvular area and of 61% in unfavorable patients, taking as a success parameter a 50% increase in the original valvular area and a decrease of the transvalvular gradient to less than 10 mm hg. we comment about procedure complications, such as severe valvular regurgitation, interatrial shunt and tamponade. procedure mortality is of 1%, especially when the valvular area is smalles than 0.7 cm2 or the wilkins score is over 13.
Corrosion Evaluation of SS-304 Stainless Steel for the Application to Heat Pumps
Arteaga,C. Cuevas; Chavarín,J. Uruchurtu; Martínez G.,Miguel A.;
Portugaliae Electrochimica Acta , 2005,
Abstract: studies of the corrosion evaluation of ss-304 stainless steel exposed in aqueous lithium bromide solution have been carried out applying the electrochemical noise technique, polarization curves and the weight loss method. the test temperatures were 50, 60 and 70 °c, and the exposure time was for fifteen days. the main objective was to determine the corrosion rates and the type of corrosion that ss-304 suffers under the mentioned conditions with the purpose of evaluating its application to heat pumps/transformers. the results showed that at the three test temperatures the type of corrosion was a mixed and pitting process. at 60 °c, it was observed some anodic peaks at the fifth day of exposure, indicating pitting nucleation. from 7 to 12 days a regular and continue pitting process was observed, and then the corrosion process became in generalized type. at 70 °c, some isolated and medium intensity peaks were observed, presenting behaviour of some mixed and pitting corrosion. the resistance noise was calculated through a statistical analysis, and then the stern-geary equation and faraday law were applied to determine the mass loss, which was compared to that obtained from weight loss method. tafel slopes were determined from experimental polarization curves. to support the metallic oxidation carried out on the stainless steel surface, atomic absorption analysis was made to the solution corrosion products.
Corrosion Evaluation of SS-304 Stainless Steel for the Application to Heat Pumps
C. Cuevas Arteaga,J. Uruchurtu Chavarín,Miguel A. Martínez G.
Portugaliae Electrochimica Acta , 2005,
Abstract: Studies of the corrosion evaluation of SS-304 stainless steel exposed in aqueous lithium bromide solution have been carried out applying the electrochemical noise technique, polarization curves and the weight loss method. The test temperatures were 50, 60 and 70 °C, and the exposure time was for fifteen days. The main objective was to determine the corrosion rates and the type of corrosion that SS-304 suffers under the mentioned conditions with the purpose of evaluating its application to heat pumps/transformers. The results showed that at the three test temperatures the type of corrosion was a mixed and pitting process. At 60 °C, it was observed some anodic peaks at the fifth day of exposure, indicating pitting nucleation. From 7 to 12 days a regular and continue pitting process was observed, and then the corrosion process became in generalized type. At 70 °C, some isolated and medium intensity peaks were observed, presenting behaviour of some mixed and pitting corrosion. The resistance noise was calculated through a statistical analysis, and then the Stern-Geary equation and Faraday Law were applied to determine the mass loss, which was compared to that obtained from weight loss method. Tafel slopes were determined from experimental polarization curves. To support the metallic oxidation carried out on the stainless steel surface, atomic absorption analysis was made to the solution corrosion products.
Efecto del pH en la corrosión de acero al carbono en presencia de un medio amargo
Esparza Zú?iga, E. M.;Veloz Rodríguez, M. A.;Reyes Cruz, V. E.;Uruchurtu Chavarín, J.;
Superficies y vacío , 2012,
Abstract: the analysis of electrochemical behaviour of carbon steel immersed in a sour water of the petroleum industry, varying the ph, was studied. different techniques used show the presence of three important corrosion stages: adsorption, species diffusion and localised corrosion. meb analysis showed the presence of corrosion products only at ph 8.5, while in all the ph tested there are cavities or pitting. the eds study confirms the presence of oxygen, calcium and chlorides at ph 8.5, where the corrosion products are present.
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
The Role of Ultrasound and Air Leak Measurement in Assessing Lung Expansion after Thoracic Surgery  [PDF]
Abraham Chavarín, Laureano Molins, Jose M. Mier, Juan J. Fibla, Cristina Izquierdo-Vidal, Cristina Simon, Angela Guirao, Jorge Hernandez
Surgical Science (SS) , 2015, DOI: 10.4236/ss.2015.68052
Abstract: Objective: To determine if lung ultrasound semiology is applicable to the post-surgical hemithorax, and its value in the evaluation of lung expansion in the postoperative period when paired with the use of digital chest drain systems. Methods: Prospective observational study including all patients undergoing thoracic surgery from June 2012 to March 2013. Patients undergoing pleurodesis or hemodynamically unstable were not considered candidates. Final inclusion in the study was based on the availability of digital chest drain system. A transthoracic lung ultrasound evaluation of the anterior and anterolateral windows was performed 20 minutes after chest drain placement. Presence or not of lung sliding and air leak values taken from the digital chest drain system were recorded. Data were submitted to a binomial classification test for analysis. Results: Forty-nine patients were included, yielding a total of 64 hemithoraces. Lung sliding was seen in 53 cases (82.8%), and an air leak value of 20 ml/min or less in 56 cases (87.5%). Sensitivity was 92.8% (95% CI: 82.6% to 97.9%) and specificity 87.5% (95% CI: 47.3% to 97.9%). Positive predictive value was 98.1%, and negative predictive value was 63.6%. Conclusions: Transthoracic lung ultrasound is a useful technique that can complement the use of digital chest drain systems in the evaluation of post-surgical lung expansion. The incorporation of lung ultrasound can greatly reduce the need for chest radiographs in thoracic surgery departments.
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
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