Mecánica

Podosphaera fusca is the main causal agent of cucurbit powdery mildew in Spain and one of the most important limiting factors for cucurbit production worldwide. As an obligate biotrophic parasite, this fungus has been traditionally cultured and conserved by periodical transfers of conidia to fresh plant material. Here we describe a simple protocol for preservation of P. fusca isolates in absence of living tissue based on the dry spore, slow-freezing technique, and demonstrate that storage of silica gel desiccated conidia at −80°C is an efficient method for the long-term preservation of the pathogen.

Fracture toughness determination shall be performed by standard test methods using specimens with valid geometry. Frequently, required specimen size can not be obtained from the material thickness to be characterize so in this case is possible to obtain fracture parameters from small specimens fracture mechanics techniques or these ones using indirect methods from Charpy-V impact energy obtained by means of standard or subsize V-notch specimens. This paper presents a side grooved Charpy-V subsized specimen in order to correct ductile to brittle transition curve and transition temperature. At the same time, a comparative evaluation has been made between fracture defect assessment methods applied to pressure vessel where the material fracture parameter was obtained either Charpy standard specimens or small ones. The results are evaluated with actual values of pressure vessel fracture failures induced by pressurized cycle test. The analysis verifies an acceptable agreement in terms of ...

RESUMEN La determinación de la tenacidad a la fractura en materiales compuestos híbridos y laminados fibra-metal - FML (Fiber Metal Laminates) - resulta muy importante para poder realizar un análisis de integridad estructural que permita estimar la tolerancia al daño y la resistencia remanente del material frente a la propagación de una fisura. Dicha evaluación debe realizarse tanto en estructuras aeronáuticas como navales que utilizan compuestos FML del tipo CARALL (CArbonReinforcedAluminumLaminates). En este trabajo se presenta la determinación experimental de la tenacidad a la fractura en términos del parámetro J utilizando probetas compactas C (T) en dos tipos de material compuesto laminado con láminas de aluminio 6061-O en un caso y láminas de aluminio 1050 en otro y fibras de carbono NCT-301 embebidas en resina epoxy para ambos materiales. Los resultados indican que la adaptación de las técnicas de ensayo de tenacidad a la fractura elastoplástica utilizadas son aceptables para...

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.

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).

We aimed at the development of a technically and economically feasible process for the use of a renewable resource, lignocellulosic biomass, in the production of an energetic resource, ethanol, which may be used also as a basic raw material for alcochemistry. We detected the relevant scientific / technological problems which to date have inhibited a generalized commercial application of a process as the one proposed. Alternatives were analyzed for each stage involved in the conversion of lignocellulose to ethanol, evaluating advantages, disadvantages, productivity, efficiency and the like. This paper sums up the technological considerations and the economic assumptions that support the use of lignocellulosic biomass as a substrate for ethanol production.

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.

Antibacterial capacity of silver is well known and has been widely documented. Nanotechnology allows the optimization of this potential by formulating materials with nanoparticles of metallic silver (NPsAg) which can slowly release silver ions that inhibit the synthesis of the bacteria cell wall, thus causing bacteria death. There exist several methods to attach nanoparticles to textile fibers, such as self-assembling polymers followed by in situ reduction and deploy ofa suspension of previously synthetized nanoparticles on substrates either in original state or surface modified. This work discusses different alternatives of silver formulated textiles as well as validation of bactericidal effect by diffusion test on cultures of Staphylococcus aureus. Textiles were prepared by two different methods: a) immersionin suspensions of NPsAg of different concentrations, followed by pressurization, and b) simultaneous application of pressure and immersion in suspensions of NPsAg. Nanoparticles of silver were prepared at Nanotek´s laboratory under a proprietary method and were characterized by SEM. Bioassays bioassay were done by the worldwide standard Kirby-Bauer antibiotic testing (KB testing or disk diffusion antibiotic sensitivity testing). This is a test which uses antibiotic-impregnated wafers (in our case silver-impregnated textiles) to test whether bacteria are affected by antibiotics (namely silver in our case). Culture media in Petri disks were inoculated with Staphylococcus aureus ATCC 25923 at a concentration equivalent to a turbidityof 0.5 in Mc Farland standard scale. The sets were incubated at 35 °C and inhibition zones were measured. Results showed a correlation between concentrations of NPsAg, amount of silver attached to substrate and biocide effect. Both techniques (sequential and simultaneous pressurization immersion) showed similar results, generating inhibition zones between 2 and 4 mm for the microorganism tested. This applied work is an example of the possibility to create entrepreneurial competitively through innovation by adequate knowledge managing at the firm. La capacidad antimicrobiana de la plata es conocida desde hace mucho tiempo. La nanotecnología permite optimizar este potencial mediante la formulación de productos con nanopartículas de plata (NPsAg) que actúan por liberación lenta de iones Ag + , reaccionando con las proteínas de la pared celular de los microorganismos, desnaturalizándolas y provocando así la inhibición de su crecimiento o la muerte. Existen varios métodos de inserción de nanopartículas en las fibras textiles, dentro de las que se encuentran autoensamblados de polímeros y reducción in situ; o depósito directo de nanopartículas en suspensión sintetizadas previamente, sobre un sustrato que puede ser modificado o no. Este trabajo presenta diversas alternativas ensayadas sobre textiles diversos así como la validación de la actividad antimicrobiana mediante un ensayo de difusión frente a Staphylococcusaureus. Las telas fueron preparadas mediante dos técnicas diferentes: a) inmersión en suspensiones de NPsAg de distintas concentraciones seguida de presurización, b) aplicación simultánea de presión e inmersión en las suspensiones de NPsAg. Las nanopartículas de plata fueron preparadas en los laboratorios de Nanotek mediante una técnica propia, y fueron caracterizadas mediante microscopía SEM. Los ensayos microbiológicos fueron realizados por el método de difusión en agar. Las placas fueron sembradas con un inóculo de Staphylococcusaureus ATCC 25923 de una concentración equivalente al estándar de turbidez de 0,5 de Mc Farland, donde se apoyaron las telas y fueron incubadas a 35 °C. Se observaron los halos de inhibición. Se demostró que la cantidad de plata depositada en las telas se correlaciona con la concentración de NPsAg, y que los resultados obtenidos mediante las dos técnicas son similares. Las telas resultaron activas frente a Staphylococcusaureus presentando todas halos de inhibición entre 2 y 4 mm. El trabajo demuestra que la adecuada gestión del conocimiento en la Empresa permite generar competitividad mediante la innovación.

Groundwater of the Chacopampean Plain of Argentina (provinces of Córdoba, La Pampa,
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

There are several soil stabilization materials that can satisfy expected performance of stabilized soils. Thus we intend to ascertain the feasibility of different options, as an alternative to costly paving of low-volume secondary roads. This evaluation was made by a Life-Cycle Cost Analysis (LCCA) considering not only initial costs, but actual Net Present Worth (NPW), aiming at maximizing the intervals of time between required maintenance activities. The alternatives considered include an array imported materials and a locally manufactured suspension of nanoiron in a copolymer matrix. As control, a basic preparation limited to shaping the surface with a motor grader as the standard unpaved road maintenance practice, was also assessed. The analysis period was 6 years, according to current data on maintenance free performance of the nano formulated alternative. The NPW analysis under these assumptions support the feasibility of the nanotechnological alternative as the less costly over the total period considered.