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Search Results: 1 - 10 of 51313 matches for " Carlos; Katime "
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Empleo de una sonda infrarroja in situ para monitorear reacciones de esterificación
Sánchez C.,Francisco J.; Cesteros,Carlos; Katime,Issa A.;
Ingeniería e Investigación , 2006,
Abstract: a batch reactor was employed having ph meter, ir probe and continuous operation detectors so that it could work as a cstr reactor. as esterification advanced, then ir bands corresponding to the carboxyl acid cooh group and the alcohol c-oh group decreased whilst a parallel increase was presented in the ester -coor group band which was forming. reaction progress could be observed by continuous ir spectrum registration. the ir band for hoh (water) could not be studied because it needed a completely anhydrous medium for doing so. standard solutions could be prepared for quantifying ir band peak intensity, according to a component?s composition in the mixture. however, when phase changes occurred in the reaction mixture, this method could not be employed for following the course of a particular reaction because random variation was detected in band intensity.
Empleo de una sonda infrarroja in situ para monitorear reacciones de esterificación Using an infrared probe for in situ monitoring of esterifying reactions
Sánchez Castellanos Francisco José,Cesteros Carlos,Katime Issa A
Ingeniería e Investigación , 2006,
Abstract: Se empleó un reactor batch (por lotes), dotado de tres detectores: pH, Sonda IR y operación en continuo, de tal forma que puede operarse como un reactor CSTR. En la medida en que la esterificación procede, decrecen las bandas correspondientes al grupo -COOH del ácido carboxIlico y la del grupo C-OH del alcohol, presentándose al mismo tiempo incremento en la banda del grupo -COOR del ester que se está formando. El progreso de la reacción se puede seguir por el registro continuo de los espectro IR. La banda correspondiente a H-O-H del agua no se puede seguir ya que se requiere de un ambiente absolutamente anhidro para hacerlo. De otro lado, por aparte pueden prepararse soluciones patrones para poder cuantificar la intensidad de los picos en el espectro IR, segün la composición del componente en la mezcla. Sin embargo, cuando se presentan cambios de fase en la mezcla reactiva, este metodo no puede emplearse para seguir el curso de una reacción, ya que se presenta una variación muy aleatoria en la senal de intensidad de los picos. A batch reactor was employed having pH meter, IR probe and continuous operation detectors so that it could work as a CSTR reactor. As esterification advanced, then IR bands corresponding to the carboxyl acid COOH group and the alcohol C-OH group decreased whilst a parallel increase was presented in the ester -COOR group band which was forming. Reaction progress could be observed by continuous IR spectrum registration. The IR band for HOH (water) could not be studied because it needed a completely anhydrous medium for doing so. Standard solutions could be prepared for quantifying IR band peak intensity, according to a component’s composition in the mixture. However, when phase changes occurred in the reaction mixture, this method could not be employed for following the course of a particular reaction because random variation was detected in band intensity.
Darunavir Resistance in HIV Infecting Protease Inhibitor-Experienced Mexican Patients  [PDF]
Carlos A. Agudelo, Luis E. Soto-Ramírez, Abraham Katime-Zú?iga, Lorena Cabrera-Ruíz, Hugo Lara-Sánchez, Juan J. Calva
World Journal of AIDS (WJA) , 2013, DOI: 10.4236/wja.2013.33035
Abstract:

Background: Darunavir (DRV) is a useful antiretroviral treatment in the salvage therapy of multiclass-resistant HIV-infected patients. This study’s aim was to determine the frequency and risk factors for DRV resistance-associated mutations (DRV-RAM) among DRV-naive Mexican patients with virologic failure after extensive antiretroviral treatment and exposure to at least one protease inhibitor (PI). Methods: HIV-infected patients with a history of at least 2 failed regimes were included and their clinical histories and genotype resistance tests were analyzed. Major PI resistance-associated mutations (PI-RAM), DRV-RAM and resistance to DRV were defined according to the IAS-USA criteria. Previous exposure to PI was compared between patients with DRV-resistant HIV and DRV-susceptible HIV-infected controls. Results: The median number of major PI-RAM was 2 (IQR = 0 - 3). In 54.7% (95% CI = 50.0% - 59.4%) of 631 subjects, no DRV-RAM were found on viral genotyping and 6.7% (95% CI = 4.8% - 8.6%) had 3 or more DRV-RAM. The two most frequently found DRV-RAM were in codons I84V (in 22.7% of cases) and L33F (in 20% of cases) in the viral protease gene. The number of major PI-RAM (as a surrogate marker of duration and number of PI used) and previous exposure to (fos) amprenavir or tipranavir were independently associated with DRV-resistant HIV infection. Conclusions: In this Mexican population, despite a high prior PI exposure, HIV-DRV resistance rate is relatively low and successful viral control with DRV-containing combined salvage therapy is expected in most patients.

Swelling Properties of New Hydrogels Based on the Dimethyl Amino Ethyl Acrylate Methyl Chloride Quaternary Salt with Acrylic Acid and 2-Methylene Butane-1,4-Dioic Acid Monomers in Aqueous Solutions  [PDF]
Issa Katime, Eduardo Mendizábal
Materials Sciences and Applications (MSA) , 2010, DOI: 10.4236/msa.2010.13026
Abstract: Hydrogels of dimethylaminoethyl acrylate methyl chloride quaternary salt (Q9) have been synthesized with different monomer ratio by copolymerization of this poorly studied monomer either with acrylic acid or with 2-methylene bu-tane-1,4-dioic acid. Hydrogel swelling was measured as a function of the composition of the hydrogel and of the crosslinking agent ratio. High values of swelling have been obtained at very high crosslinking values (< 14 wt %) and the equilibrium swelling was reached at very low time (less than 15 minutes). The swelling isotherms consisted of a steep initial portion and then levelled off as asymptotically to the equilibrium swelling limit. The experimental data suggest clearly that the swelling process obeys second-order kinetics. According to this, the kinetics rate constant and the equilibrium water content were determined at different comonomer composition and crosslinker concentration. The calculated kinetic constants ranged from 0.48 to 3.76 × 10-2 min-1 for poly (acrylic acid-co-Q9) hydrogels and from 0.68 to 4.0 × 10-2 min-1 for poly (2-methylene butane-1,4-dioic acid-co-Q9) hydrogels depending on the hydrogels composition. The diffusion process was evaluated for each hydrogel showing a non-Fickian type diffusion. In all cases was observed a considerable increase in diffusion coefficient as Q9 content increases.
Cationic Microemulsion Polymerization of Alkyl Acrylates  [PDF]
Issa Katime, Jesús Arellano, Eduardo Mendizábal, Jorge Flores
Materials Sciences and Applications (MSA) , 2010, DOI: 10.4236/msa.2010.15043
Abstract: Here we present the polymerization of n-butyl acrylate (BA), ethyl acrylate (EA) and methyl acrylate (MA) in tri-component microemulsions, using a cationic surfactant such as dodecyl trimetyl ammonium bromide in water, as a function of temperature, initiator type and, monomer and initiator concentration. The final latexes are transparent and blue color, with particle size ranging between 20 and 60 nm determined by quasielastic light scattering (QLD) and SEC molar masses of the order of 106 g/mol. Reaction times are short and reaction rates are high with final conversions between 70 and 98% depending on the monomer and the reaction conditions.
Hydrogels obtained from acrylamide, maleic acid, acrylic acid and octylmonoitaconate: synthesis, absorbent capacity and pH variations in copper sulfate solutions
Rojas de Gascue,Blanca; Ramírez,Marvelis; Aguilera,Rocelis; García,Augusto; Prin,José Luis; Lias,José; Torres,Carlos; Katime,Issa;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2007,
Abstract: abstract acrylamide (aam)/maleic acid (am), acrylic acid (aac)/maleic acid (am) and acrylic acid (aac)/2 - methylenebutanedioic acid octylesther (mi-8) hydrogels were sinthetysed in presence of amonium persulfate as initiator and n,n?-methylenebisacrylamide as crosslinking agent. the grade of hydrogels swelling was determined by two test at diferent temperatures: 25 and 37°c. the hydrogels swelling also was studied in divalents cations salts solutions, like copper by way of plasma spectroscopy emition. the swelling of synthesised hydrogels test shows isothermal that extends asinthotically to the equilibrium. it was demonstrated that the maleic acid content had a direct influence in the swelling properties (an increment of 30% in am rise the content of water in the hydrogel in 12%). respect to the copper cations adsorption, we found that the concentration decrease in the initial solution after to be in contact with the hydrogels. moreover, ph variation was measured allowing understand the reaction mechanism between the hydrogels and metallic ions
New Family of Functionalized Monomers Based on Amines: A Novel Synthesis that Exploits the Nucleophilic Substitution Reaction  [PDF]
Lissette Agüero, Luis G. Guerrero-Ramírez, Issa Katime
Materials Sciences and Applications (MSA) , 2010, DOI: 10.4236/msa.2010.13018
Abstract: Chemistry modifications are usually performed to introduce specific group that can increase properties and functionality of materials. In this study, we present the synthesis of six new functionalized monomers prepared by nucleophilic substitution reactions. Reaction of aliphatic and aromatic amines with acryloyl chloride at –20ºC, in presence of triethylamine allowed the synthesis of the corresponding amides. Proton nuclear magnetic resonance (1H NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and ultraviolet- visible (UV-Vis) measurements confirmed the success of the synthesis with a yield over 90%. These compounds emerged as potentially attractive monomers since they can be used to obtain stimuli-sensitive polymeric materials, due to the presence of amide and pyridine groups.
Polymeric Nanohydrogels of Poly(N-Isopropylacrylamide) Combined with Others Functionalized Monomers: Synthesis and Characterization  [PDF]
Lissette Agüero Luztonó, Yuneivy Cepero Donates, Luis Guillermo Guerrero Ramirez, Addys González Palomo, Dionisio Zaldivar Silva, Issa Katime
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2014, DOI: 10.4236/jbnb.2014.51005
Abstract:

Nanohydrogels from inverse microemulsion (w/o) polymerization, at 25°C, of N-isopropylacrylamide (NIPA) and functionalized monomers are described. The functionalized monomers were: N-(pyridine-4-ylmethyl) acrylamide (NP4MAM) and tert-butyl 2-acrylamidoethyl carbamate (2AAECM). The polymeric nanohydrogel obtained was characterized by attenuated total reflectance Fourier-transformed infrared spectroscopy (ATR-FTIR) and proton nuclear magnetic resonance spectrometry (1HNMR), while their morphology and particle size was assessed by scanning electron microscopy (SEM) and dynamic light scattering. Their thermal properties were studied by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). As a preliminary measure of biocompatibility, in vitro evaluations of the nanohydrogels were carried out by cellular toxicity (colon carcinoma cells, CT

Hepatitis aguda por dengue virus y hepato-toxicidad por acetaminofén: A propósito de un caso
Katime Zú?iga,Abraham; Suárez Parejo,César;
Revista Colombiana de Gastroenterologia , 2005,
Abstract: the dengue is a zoonosis viral?s etiology with mundial high incidence. its clinical spectrum is wide from clasicc dengue until hemorragic dengue shock. the hepatitis is a frecuent complication in this patients, and we must distinguish from other virals hepatitis for predominate ast upon alt, moreover , there are cases associates with acetaminofén hepatotoxicity.
Hepatitis aguda por dengue virus y hepato-toxicidad por acetaminofén: A propósito de un caso
Abraham Katime Zú?iga,César Suárez Parejo
Revista Colombiana de Gastroenterologia , 2005,
Abstract: El dengue es una zoonosis de origen viral de alta incidencia a nivel mundial. Su espectro clínico comprende desde el dengue clásico hasta el síndrome de shock por dengue hemorrágico. La hepatitis es una complicación frecuente en los pacientes con dengue, y se debe diferenciar de otras hepatitis de origen viral por el predominio de AST sobre ALT, además, en estos pacientes se ha descrito de forma asociada hepatotoxicidad por Acetaminofén. The Dengue is a zoonosis viral’s etiology with mundial high incidence. Its clinical spectrum is Wide from clasicc dengue until hemorragic dengue shock. The Hepatitis is a frecuent complication in this patients, and we must distinguish from other virals hepatitis for predominate AST upon ALT, moreover , there are cases associates with Acetaminofén hepatotoxicity.
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