Papers by Gerardo D López
Computer Aided Chemical Engineering
Revista Latinoamericana De Metalurgia Y Materiales, 1984
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Medicina, 1993
The use of surgical implants and prosthetic devices to replace the original function of different... more The use of surgical implants and prosthetic devices to replace the original function of different components of the human biological system is a well established tradition in the history of medicine. Currently, one of the most prevalent points of view in dealing with this subject, is that of biocompatibility of materials of construction and methods of fabrication of these devices, in order to avoid negative impacts on the patient due to failure of implants through degradation mechanisms such as corrosion. This article presents a current general review of the relationship between biocompatibility and deterioration of metallic implants and prosthetic devices, emphasizing the specific forms that corrosion adopts in biological media. The historical perspective shows the consolidation of a tendency towards a more systematic study of these phenomena in recent years, as opposed to trial and error practices that used to be common before the third decade of this century. The understanding of...
Ingenieria Quimica, 2004
Definir el capital requerido para poner en marcha un proyecto se presenta como un factor clave an... more Definir el capital requerido para poner en marcha un proyecto se presenta como un factor clave ante la decision de su realizacion: para cuantificar criterios ante su aceptacion o rechazo. Sin embargo, en las fases de evaluacion preliminar de un proyecto, no se dispone como referencia de bases de datos completas y actualizadas: los potenciales proveedores no estan dispuestos a proporcionar sus costos, a menos que tengan alguna garantia de que finalmente seran seleccionados; el desarrollo del proceso puede no estar optimizado; los propios costos de llevar a cabo estimaciones precisas resultan elevados, porque entre otras circunstancias requieren un equipo de especialistas y un conocimiento acabado de procesos y equipos involucrados. Estas situaciones se agudizan en las pequenas y medianas empresas, ya sea por falta de recursos o por su idiosincrasia. Los "bemoles" de la estimacion La dinamica que caracteriza la realidad economica obliga a las empresas vinculadas a la fabrica...
Marine Environmental Research, 2013
We assessed the persistence of expected bactericidal performance (standard test of diffusion in a... more We assessed the persistence of expected bactericidal performance (standard test of diffusion in agar) derived from washing synthetic textiles dosed with nanosilver. Two kinds of textiles were tested (polyester plus elastin and polyamide plus elastin), and then subject to washing cycles employing a commercial brand of soap. For polyamide, bactericidal capacity diminishes after the first cycle of washing, but afterwards it reaches a constant value. Polyester resists reasonably well the first washing, but bactericidal activity is practically zero from the second cycle of washing onwards. Thus, we conclude that persistence of bactericidal capacity is related to the composition of synthetic textiles, which interact chemically with nanosilver with varying strength. This conclusion set the path to further research on improving binding capacity of nanometal to polymers, in order to extend useful life of clothing and minimize environmental impact.
We aimed at the use of lignocellulosic boas in the production of a food preserving agent that may... more We aimed at the use of lignocellulosic boas in the production of a food preserving agent that may achieve categorization as “natural” in the terms of Section 21 CFR 101.22 (A) of the US FDA. The basic approach was to detect relevant technological bottlenecks which to date have inhibited a generalized commercial application of a process as the one proposed. Processes and raw matter alternatives were analyzed for technical feasibility and reasonable yields, assessing advantages, disadvantages, productivity, efficiency and the like. This paper sums up the results achieved by the multidisciplinary team involved in the project.
Preservation of fruits and vegetables is important sanitarily as well as economically. This work ... more Preservation of fruits and vegetables is important sanitarily as well as economically. This work reports results from exposure of pears during 36 days to a natural open environment, without cooling. The samples were protected by two different means: individual wrapping with a nanosilver dosed film, and nanosilver formulated cardboard. Samples were triplicated. Efficacy of preservation was followed by daily visual inspection. At the end of the test period, all the fruits were opened to assess visually the progress of deterioration from the skin to the heart of the fruits. Best results were achieved with the nanometal formulation of the cardboard container. Individual wrapping resulted in earlier and more intensive deterioration, probably due to the generation of a microenvironment with little air renewal and consequent increase in local relative humidity. Blank samples were the most degraded, as was to be expected. We conclude that the best strategy is to dose nanosilver directly int...
Se pueden distinguir dos grandes enfoques conceptuales en el análisis del emprendedorismo: por un... more Se pueden distinguir dos grandes enfoques conceptuales en el análisis del emprendedorismo: por un lado el énfasis sobre las características personales de los hacedores (innatas o adquiridas) y por el otro la consideración de las influencias contextuales (entorno social y económico, formación). Si bien, indudablemente, ambos aspectos tienen influencia sobre la cuestión, el hecho que existan emprendedores con independencia de lo favorable o desfavorable de las condiciones políticas y económicas o del nivel de desarrollo de cada país (y de cada región dentro de un país) hace que nos inclinemos por la personalidad y la actitud de los individuos como parámetros de mayor influencia que los contextuales. Avanzando sobre dicha consideración, nuestra hipótesis básica es que los emprendedores no presentan rasgos psicológicos que los distingan particularmente de lo que es considerado normal en el grupo social al que pertenecen (cualquiera sea éste). Por lo tanto resulta deseable entender como hacen para encontrar oportunidades y negocios donde otros solo ven problemas. Con este objeto, postulamos que la auto percepción, el análisis de como se ven a si mismos los emprendedores, puede permitirnos encontrar ese intangible que motoriza el empeño que ponen en llevar adelante su idea hasta concretarla. Adoptamos así la metodología de entrevistas guiadas de larga duración tanto a emprendedores potenciales como a emprendedores con negocios en marcha. El trabajo de campo permite concluir que el factor de mayor importancia que los hace perseverar con la idea hasta concretarla se relaciona más con la intuición que con el razonamiento de manera que no es la evaluación formal del proyecto
Fullerene (nC60) and nanosilver (nAg) are nanomaterials with bactericide properties. The incremen... more Fullerene (nC60) and nanosilver (nAg) are nanomaterials with bactericide properties. The increments in their use raise questions about their potential environmental impacts, including estuarine ones. The polychaete Laeonereis acuta (Nereididae) secretes mucus that is colonized by bacteria communities. We analyzed the antioxidant and oxidative damage responses of anterior, middle and posterior region of L. acuta and bacteria communities after nC60 or nAg exposure during 24 h. Molecular analysis showed a prevalence of Vibrio genera in the communities. Bacteria biomass was lowered in worms exposed to 1.0 mg/L of nAg. nC60 reduced total antioxidant capacity of bacteria from worms exposed to 0.1 mg/L. Worms anterior region presented lower antioxidant capacity after exposure to 1.0 mg nC60/L, and the same was observed in the posterior region of worms exposed to 1.0 mg nAg/L. Lipid peroxidation was reduced in the anterior region of worms exposed to nC60 and the opposite was observed in the posterior region.
The main object of this work was to develop an antimicrobial polyester fiber by a polyelectrolyte... more The main object of this work was to develop an antimicrobial polyester fiber by a polyelectrolyte deposition technique and silver nanoparticles formation in situ. Attached silver metallic nanoparticles (Ag°NPs) work like silver cations reservoir (Ag+); and in a wet medium are released to the environment. Silver cations act against microorganisms, reacting with cellular walls proteins, denaturing and producing an alteration growth or cellular death. Textiles were prepared by a layer by layer technique: two opposite charged polyelectrolytes are deposited in an alternative form; PAH (poly-allylamine hydrochloride, positive charge) and PAA (,polyacrilic acid negative charge), producing two bilayers (2PAH/PAA). Fibers are then immersed in a AgNO3 solution for some time, to let the Ag+ diffusion onto the polymeric net, and then they were reduced by NaBH4 to form silver nanoparticles (Ag°NPs). The Silver amount achieved was between 5.5 and 7.7 mg Ag / 100 gr fiber. These textiles were tested against Staphylococus aureus, obtaining a good result in the growth inhibition.
This study analyzed the growth and biochemical responses of six bacterial colonies isolated from ... more This study analyzed the growth and biochemical responses of six bacterial colonies isolated from the mucus of the estuarine polychaeta Laeonereis acuta (Nereididae) after exposure to a water suspension of fullerene (nC 60) and nanosilver (nAg) separately (0.01; 0.10; and 1.00 mg/L) and together (0.01; 0.10; and 1.00 mg/L of nanosilver and 1.00 mg/L of fullerene added to each nAg concentration). Exposures were performed in darkness during 24 h and then samples were taken from the worms and inoculated on agar during 24 h to analyze colonies growth. After this the material was analyzed biochemically. Colonies growth (tested by wet biomass weight) was inhibited at 0.01 and 0.10 mg/L of nAg and 0.01 and 0.10 mg/ L nAg þ constant 1.00 mg/L of nC 60 (p < 0.05). Lipid peroxidation damage was significant from the control for the concentrations of 0.01 and 0.10 mg/L of nC 60 and glutathione-S-transferase (GST) activity was significantly higher for the concentration of 1.00 mg/L mg/L nAg þ constant 1.00 mg/L of nC 60 (p < 0.05). Although nC 60 did not induced growth inhibition, it triggered lipid peroxidation alone and increased GST activity together with nAg. 60 Contrary to nC 60 , nanosilver inhibited bacterial growth, although the biochemical measurements indicate that this response is not due to reactive oxygen species generation.
The use of surgical implants and prosthetic devices to replace the original function of different... more The use of surgical implants and prosthetic devices to replace the original function of different components of the human biological system is a well established tradition in the history of medicine. Currently, one of the most prevalent points of view in dealing with this subject, is that of biocompatibility of materials of construction and methods of fabrication of these devices, in order to avoid negative impacts on the patient due to failure of implants through degradation mechanisms such as corrosion. This article presents a current general review of the relationship between biocompatibility and deterioration of metallic implants and prosthetic devices, emphasizing the specific forms that corrosion adopts in biological media. The historical perspective shows the consolidation of a tendency towards a more systematic study of these phenomena in recent years, as opposed to trial and error practices that used to be common before the third decade of this century. The understanding of interactions between implants and biological tissue, thus led to some of the most promising current techniques, such as the use of powder metallurgy components to optimize skeletal fixation of implants by means of interstitial bone growth into porous metallic surfaces. The review of metals and alloys currently used for the fabrication of implants shows the amplitude of available technological alternatives, as well as the multiple criteria required to make a good selection for each specific case. Applications and pros and cons of stainless steel, Cr, Ni, Co and Ti alloys, and tantalum are briefly discussed. The introduction to basic concepts of corrosion, serves as a basis for the description of the typical forms that these phenomena adopt in biological media, including pitting, crevice corrosion, fatigue-corrosion, stress corrosion, fretting corrosion, galvanic corrosion, and intergranular corrosion. This review shows that the study of interactions between biological media and metallic implants has become a well established and specific field of science. As a result of this conclusion, an interdisciplinary treatment of the subject of biodeterioration of metallic implants and prosthetic devices is proposed. In practical terms, this proposal can be understood as the integration of an expert in materials science and engineering to the medical team. Thus, quality and reliability of the implant, as well as maximization of its useful life, would be achieved through the implementation of technical specifications, accepted standards, and pertinent testing as recommended by the above mentioned expert, who will be the person of the team more able to grasp the novelties that the dynamic field of biomaterials constantly offers.
Results on As(V) removal in the presence of oxygen using the zerovalent iron technology with comm... more Results on As(V) removal in the presence of oxygen using the zerovalent iron technology with commercial iron nanoparticles (NanoFe®) are presented, showing the effect of (NanoFe®) mass, UV light and addition of humic acids. The nanosized iron particles (NZVI) were characterized in their particle size, surface area and constituent phases. As(V) removal was rapid and increased with NZVI mass (0.005–0.1 g L−1) attaining more than 90% after 150 min of time contact with the optimal NanoFe® concentration. The removal followed a biexponential kinetic decay, with rate constants increasing with NZVI mass. (NanoFe®) presented an outstanding ability to remove As due to not only a high surface area and low particle size but also to a high intrinsic activity. Humic acids (HA) decreased around 50% the removal efficiency in the dark, indicating competition with As(V) for active surface sites. In contrast, UV light doubled removal rates, the process being even more enhanced in the presence of HA, with an almost total arsenic removal within 4 h. In all cases, adsorption on iron corrosion phases was found the main mechanism of As(V) removal, promoted by formation of Reactive Oxygen Species and enhanced under UV irradiation by the formation of multiple active species. Preliminary results with As-polluted groundwater of the Chacopampean Plain of Argentina (Tucumán Province) are also reported. Addition of NanoFe® under UV irradiation for 3 h resulted in As contents well in agreement with the regulations (<10 μg L−1).
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Papers by Gerardo D López
Santa Fe and Buenos Aires) contain levels of arsenic (As) well above the 10 μg L−1 limit
established by the Food Argentine Code (Código Alimentario Argentino 2007), same as recommended by WHO (WHO 2004) (10 μg L−1). These groundwaters present high salinity,
and the As concentrations are generally well correlated with those of other anions (F, V,
HCO3−, B, Mo). Waters are predominantly oxic, and have high pH values (7.0–8.7). Hence,
As is mainly present as As(V) (Smedley et al. 2002). Metal oxides in the sediments (especially
of Fe and Mn) are probably the main source of dissolved As as reported by Smedley et al.
(2002), although the dissolution of volcanic glass has also been cited by Nicolli et al. (1989)
as a potential source.
In many rural areas of the region, the lack of a drinking water network distribution and
the absence of important surface water bodies make necessary to extract water from deep
and shallow wells, typically used without any further treatment. In general, water quality is
poor, especially in the phreatic zone, because of the bacteriological content and high levels of
chemical contaminants and trace elements (Nicolli et al. 1989). This, together with poverty
and malnutrition conditions, causes the incidence of water-borne diseases, including chronic
endemic regional hydroarsenicism (HACRE in Spanish).
Various methods are known to be useful to remove As from drinking water, including
anion exchange, precipitation, ion flotation, and adsorption (Edwards 1994, Hering et al.
1997, Pirnie 2000). Attention has recently focused on advanced oxidation processes (AOPs)
such as heterogeneous photocatalysis (HP) (Litter 2009, Yang et al. 1999, Dutta et al. 2005,
Ferguson et al. 2005, Yoon et al. 2009) and zerovalent iron (ZVI) (Bang et al. 2005, Su and
Puls 2001), considered simple and low-cost technologies to remove As from groundwater that could be applied in poor isolated villages or settlements. HP is an AOP based on the use of a non-expensive semiconductor