luis rios - Academia.edu (original) (raw)

Papers by luis rios

2008 Electronics, Robotics and Automotive Mechanics Conference, 2008

... Maximiliano Bueno Lopez max@ohm.utp.edu.co Santiago Sánchez Acevedo ssa@ohm.utp.edu. co ... a... more ... Maximiliano Bueno Lopez max@ohm.utp.edu.co Santiago Sánchez Acevedo ssa@ohm.utp.edu. co ... an efficient way the control laws, the following paradigms are applied: • Neuronal Networks and support vector machine as a model of classification and recognition of pat-terns. ...

Biomedical optics express, 2014

We present the development of a source of deep-red radiation for photoacoustic imaging. This sour... more We present the development of a source of deep-red radiation for photoacoustic imaging. This source, which is based on two cascaded wavelength conversion processes in aperiodically poled lithium niobate, emits 10 nanosecond pulses of over 500 µJ at 710 nm. Photoacoustic images were obtained from phantoms designed to mimic the optical and acoustic properties of oral tissue. Results indicate this device is a viable source of optical pulses for photoacoustic applications.

El defi ciente desempeño del biodiesel de aceite de palma (BAP) a bajas temperaturas constituye s... more El defi ciente desempeño del biodiesel de aceite de palma (BAP) a bajas temperaturas constituye su mayor defi ciencia de calidad y el limitante para propiciar el uso de este combustible alternativo para motores diesel puro o mezclado en altas proporciones con el combustible diesel convencional derivado del petróleo (ACPM). En este trabajo se evalúan varias alternativas para mejorar las propiedades de fl ujo a baja temperatura (PFBT) del BAP. Mediante la producción del biodiesel utilizando alcoholes ramifi cados como el isopropanol, isobutanol, 2-butanol e isopentanol se obtienen alquilésteres del aceite de palma con puntos de nube y fl uidez más bajos que los correspondientes a los metilésteres. La sustitución del grupo metil por el isopentil permite obtener reducciones en los puntos de nube y fl uidez de 8 y 21 ºC, respectivamente. Los isopropilésteres del aceite de palma poseen un punto de nube 10 ºC menor que el de los metilésteres. El punto de nube de las mezclas BAP-ACPM se incrementa en forma lineal con el contenido del biodiesel en la mezcla. Para las mezclas probadas (B5, B20 y B30) solo se presentan problemas de fi ltrabilidad del combustible a temperaturas por debajo de -4 ºC. En este trabajo se evaluó la efectividad de dos aditivos comerciales mejoradores de fl ujo para reducir el punto de obstrucción de fi ltros en frío (POFF) del biodiesel puro y las mezclas probadas. Los resultados obtenidos mostraron que con dichos aditivos

Información tecnológica, 2013

Frontiers in Optics, 2003

We report a technique for injection-seeding optical parametric generation (OPG) in periodically p... more We report a technique for injection-seeding optical parametric generation (OPG) in periodically poled lithium niobate in which the wavelength of the seed is neither that of the signal nor of the idler waves; instead, it is the wavelength resulting from the sum-frequency mixing of the pump and signal waves. We show that pulsed OPG can be appropriately seeded in this way even if the sum-frequency process is not quasi-phasematched if a pulsed laser is used as a seed, and if it is quasi-phase-matched even a low power (15 mW) HeNe beam can substantially reduce the bandwidth of the generated signal wave. all solid-state narrow bandwidth optical parametric oscillator and its applications to the high resolution spectroscopy of free radicals," J.

Información tecnológica, 2011

Se estudió un método de purificación para la glicerina procedente de la producción de biodiesel d... more Se estudió un método de purificación para la glicerina procedente de la producción de biodiesel de aceite de palma, para alcanzar los estándares requeridos para su uso en aplicaciones que no requieran el grado USP (United States Pharmacopoeia), definidos por las normas técnicas colombianas. Se usó diseño factorial 2 3 con tres variables: tipo de ácido (fosfórico o sulfúrico), cantidad de metanol y pH. Se encontró que el tratamiento con ácido sulfúrico, con 50% de metanol y pH de 6, es el que da mejores resultados y que se requiere una decoloración con carbón activado para cumplir con la exigencia de color. La glicerina refinada y decolorada obtenida cumple con los requerimientos de la glicerina tipo 2 grado 1 y 2 según la Norma Técnica colombiana NTC1274.

Industrial Crops and Products, 2013

A new modification of the Prileschajew method to produce hydroxylated vegetable oils using in sit... more A new modification of the Prileschajew method to produce hydroxylated vegetable oils using in situ generated peracetic acid and acidic resins, of the sulfonated polystyrene type, as heterogeneous catalysts is reported. Jatropha oil methylesters were chosen as model substrate. Reaction mixtures were characterized by 1 H NMR and gas chromatography. The effect of cross-linking degree of the resins on the conversion and the selectivity to glycols was analyzed. Best results were obtained with Amberlyst 15 catalyst, ca. 100% conversion and 80% selectivity at 57 • C over 24 h, stable through five re-uses.

Chemical Engineering Journal, 2012

Resumen Se muestran los resultados experimentales de la síntesis de cetales de glicerina para su ... more Resumen Se muestran los resultados experimentales de la síntesis de cetales de glicerina para su uso como aditivos que mejoren las propiedades de flujo a baja temperatura de un biodiesel de aceite de palma. Se evalúo su producción empleando catalizadores ...

In the epidermis, β1 integrin expression is normally confined to the basal layer; however, suprab... more In the epidermis, β1 integrin expression is normally confined to the basal layer; however, suprabasal expression of β1 integrins in keratinocytes has been found in psoriasis, and it has been suggested that it could be a pathogenic factor of the disease. We have investigated herein the functional state of β1 integrins of human keratinocytes in normal skin and psoriasis. The expression of β1-activation-reporter epitopes was monitored with two monoclonal antibodies, HUTS-21 and MG5A7, that recognize epitopes whose expression parallels functional activity of β1 integrins and correlates with the ligand binding activity of these heterodimeric glycoproteins. We have found that keratinocytes express activation epitopes of β1 integrins, and that these epitopes can be

Introduction. The Panama ICBG maximizes the role of the host country to discover new lead compoun... more Introduction. The Panama ICBG maximizes the role of the host country to discover new lead compounds from plants, algae and marine invertebrates for the treatment of cancer and tropical disease. The program has strengthened scientific research in Panama and produced tangible results for biodiversity conservation.

Planta Medica, 2006

Our previous studies on G. dumetorum yielded several aporphine alkaloids that showed significant ... more Our previous studies on G. dumetorum yielded several aporphine alkaloids that showed significant activity against Leishmania spp.

International Journal of Biological Macromolecules, 2009

Curdlan from Agrobacterium sp. was oxidized using 2,2,6,6,-tetramethylpiperidine-1-oxyl radical (... more Curdlan from Agrobacterium sp. was oxidized using 2,2,6,6,-tetramethylpiperidine-1-oxyl radical (TEMPO)–NaBr–NaClO systems at pH 11. The effects of oxidation conditions on degrees of oxidation and polymerization of the products obtained were studied using SEC–MALLS, NMR and IR analyses. Different families of water-soluble β-(1,3)-polyglucuronic and β-(1,3)-polyglucoglucuronic acid sodium salts were quantitatively generated with a yield of 80% and without significant loss of their molecular weights.Given that β-(1,3)-polyglucuronic acids prepared from the regioselective oxidation of curdlan by the TEMPO–NaBr–NaClO systems regularly consist of the glucuronic acid repeating unit; they may open new biotechnological fields for the utilizations of water soluble forms of curdlan.

Clinical Neurophysiology, 2006

Background: Parkinson's disease has a combination of motor impairment, cognitive deficits and aut... more Background: Parkinson's disease has a combination of motor impairment, cognitive deficits and autonomic dysfunction. It is not known if there exists some degree of interdependence between autonomic and cognitive dysfunction.

Annals of Anatomy - Anatomischer Anzeiger, 2013

From a comparative study of 222 human and 261 nonhuman primates complete cervical spines, two bon... more From a comparative study of 222 human and 261 nonhuman primates complete cervical spines, two bony variants associated to the course of the vertebral artery are proposed as unique to genus Homo within primates. First, the opening of the foramen transversarium at C2, a trait present at low frequency in humans (3 to 5.6%). Second, the presence of a bipartite foramen transversarium in the cervical segment C3-C6, a trait that can be observed fully formed in human fetal skeletons, with a clear frequency pattern along the cervical spine (C3 > C4 > C5 > C6 < C7), and the expression of which does not seem to be significantly associated to sex or side. A clear difference is observed in the frequency of a third trait, the foramen transversarium at C7, present in all the human spines studied, practically absent in Strepsirrhini, at low frequency in Platyrrhini, and generalized in Catarrhini. These findings, together with previous data regarding absence and presence of foramina at C1, indicate a pattern of gain and loss of foramina in the transverse process of the cervical vertebrae for genus Homo. The test of a possible explanation of these differences as associated to anatomical changes of the cervical spine due to erect posture and bipedal locomotion needs further research in the morphology and function of the primate cervical spine.

El objetivo de este trabajo es resumir los resultados de los principales estudios de crecimiento ... more El objetivo de este trabajo es resumir los resultados de los principales estudios de crecimiento infantil que se han realizado en Guatemala. Estas investigaciones nos muestran que el tamaño y la forma corporal, medidos a través de la estatura y de la longitud relativa de la pierna, son extremadamente sensibles al ambiente económico, social y político bajo el que crecen diferentes grupos de niños guatemaltecos. Por tanto estos estudios pueden emplearse como una evaluación desde el punto de vista del bienestar biológico de las poblaciones de una determinada estructura socioeconómica. Se comentan brevemente algunas implicaciones sociales.

Actas Dermo-Sifiliográficas, 2005

Journal of natural …, 2003

Five novel cassane diterpenes (1-5) with activity against Trypanosoma cruzi were isolated from le... more Five novel cassane diterpenes (1-5) with activity against Trypanosoma cruzi were isolated from leaves of Myrospermum frutescens. The structures were determined as 18-hydroxycassan-13,15-diene (1), 6 ,-18-dihydroxycassan-13,15-diene (2), 6 -hydroxy-18-acetoxycassan-13,15-diene (3), 18-acetoxy-13,15-diene-19-cassanoic acid (4), and 6 ,13 -dihydroxy-18-acetoxycassan-14 ,15-diene (5). Structures were elucidated by spectroscopic analysis (NMR and HRCIMS) and by the synthesis of derivatives 2a and 2b. Compounds 3 and 5 were more active against the extracellular form of the parasite (11 and 16 µM, respectively) than the intracellular forms, while compounds 1 and 2 were more active against the more clinically relevant intracellular forms of the parasite (17 µM). Compounds 1 and 2 were approximately 9-fold more toxic toward T. cruzi than toward human fibroblasts, the cell type that serves as the parasite's mammalian host cell.

Comparative Biochemistry and Physiology-Part A: …

Human body size and body proportions are interpreted as markers of ethnicity, 'race,' adaptation ... more Human body size and body proportions are interpreted as markers of ethnicity, 'race,' adaptation to temperature, nutritional history and socioeconomic status. Some studies emphasize only one of these indicators and other studies consider combinations of indicators. To better understand the biocultural nature of human size and proportions a new study of the growth of Maya-American youngsters was undertaken in 1999 and 2000. One purpose of this research is to assess changes in body proportion between Maya growing up in the US and Maya growing up in Guatemala. Height and sitting height of 6-12-year-old boys and girls (ns360) were measured and the sitting height ratio wsitting heighty heightx=100, a measure of proportion, was calculated. These data are compared with a sample of Maya of the same ages living in Guatemala and measured in 1998 (ns1297). Maya-American children are currently 10.24 cm taller, on average, and have a significantly lower sitting height ratio, (i.e. relatively longer legs, averaging 7.02 cm longer) than the Guatemala Maya. Maya-American children have body proportions more like those of white children in the US than like Maya children in Guatemala. Improvements in the environment for growth, in terms of nutrition and health, seem to explain both the trends in greater stature and relatively longer legs for the Maya-Americans. These findings are applied to the problem of modern human origins as assessed from fossil skeletons. It has been proposed that heat adapted, relatively long-legged Homo sapiens from Africa replaced the cold adapted, relatively short-legged Homo neandertalensis of the Levant and Europe wJ Hum Evol 32 (1997a) 423x. Skeletal samples of Maya adults from rural Guatemala have body proportions similar to adult Neandertals and to skeletal samples from Europe with evidence of nutritional and disease stress. Just as nutrition and health status explains the differences in the body proportions of living Maya children, these factors, along with adaptation to climate, may also explain much of the differences between the Neandertal and African hominid samples. ᮊ