Challenges in Protein Formulation Focused on Extrusion-Spheronization Process Ravetti, Soledad; Hergert, Lisandro Yamil; Sparo, Mónica Delfina; Sanchez Bruni, Sergio Fabian; Palma, Santiago Daniel Biotechnology revolution had led the overcoming of different types of therapeutic protein because of theirchemical structure can perform specific reactions in the body, increasing efficacy and decreasing side effects.Numerous efforts were made to optimize the physicochemical properties of the proteins used for therapeuticand studied different methods for an effective administration of the protein contained in the medicine,evaluating different routes of administration to achieve the desired therapeutic effects. The delivery systemfor oral pharmaceutical proteins and peptides is still in development stage. There are number of limitationsto oral delivery of proteins such as barriers to peptide bioavailability after oral administration, intestinalmembrane permeability, size, intestinal and hepatic metabolism and solubility. Pellets have shown greatpotential in the delivery of proteins/peptidal drugs. Some strategies of development of oral protein andpeptides has always been challenged, optimizing the safety and efficacy while ensuring the ability tomanufacture the drug while maintaining quality and stability. The pelletization techniques have beenreviewed in numerous papers, is a technique that enables the formation of spherical beads or pellets with amean diameter usually ranging from 0.5-2.0 mm. Pellets are prepared by different techniques, such asextrusion and spheronization. This review discusses challenges in protein formulation that have been used toprepare pelletized dosage forms using the extrusion-spheronization process.

Centro histórico de Quito : aportes para reflexionar sobre la preservación de las casas patio desde el estado de concientización usuaria; Historical Center of Quito : an experience for the preservation of courtyard houses with an emphasis on user awareness Sanchez, Lorena Marina; Woolfson, Olga La temprana declaración de Quito como Patrimonio de la Humanidad en 1978 la convierte en un ejemplo latinoamericano con una singular experiencia preservacionista. Su Centro Histórico compone una amalgama de períodos y bienes, destacándose la presencia del sincretismo español-aborigen. Esta hibridación sobrevive en el área de amortiguación, compuesta por diferentes barrios, a través de una tipología residencial característica: las casas patio. Con un sinfín de complejidades para su tratamiento, estas viviendas componen gran parte de la identidad habitacional quiteña, aunque sólo recientemente han adquirido un nuevo protagonismo dentro del marco de protección residencial. Por ello y mediante un abordaje histórico-arquitectónico y social, se ha indagado el fragmento patrimonial del barrio San Juan, representativo de lo que acontece en el área de amortiguación. Desde una concepción de la investigación exploratoria, de carácter principalmente cualitativo y centrada en la concientización de los usuarios, se exponen los diagnósticos y lineamientos de acción asociados. Esta aproximación se ha realizado mediante la observación in situ, el análisis de planimetrías, bibliografía y fotografías, la realización de entrevistas y encuestas de opinión. De esta forma se presentan reflexiones finales junto con un desarrollo metodológico factible de ser apropiado a otros bienes residenciales en otros contextos urbanos.; The early declaration of Quito as a World Heritage site in 1978, makes this city a Latin American example with a remarkable preservationist experience. Its Historical Centre composes a blend of periods and goods, emphasizing on the presence of Spanish-Aborigine syncretism stands. This hybridation survives in the buffer area, made up of different neighborhoods, through a residential property typology: the patio houses. With endless complexities to their approach, these homes comprise the residential identity of Quito, but they have only recently taken on a new protagonism within a residential protection framework. Therefore, and through a historical-architectural and social approach, has been investigated the patrimonial fragment of the neighbourhood of San Juan, which is representative of what happens in the buffer area. Diagnosis and guidelines are exposed from a conception of exploratory study, mainly qualitative and focused on users awareness. This approximation has been carried on through the observation in situ, the analysis of planimetry, bibliography, photographs, the carrying out of interviews and opinion polls. Thus, final reflections are presented along with a methodological development feasible of being adapted to other residential properties in other urban contexts.

Notelmis Hinton y Onychelmis Hinton (Coleoptera: Elmidae: Elminae) de Colombia: claves taxonóicas ilustradas; Notelmis Hinton y Onychelmis Hinton (Coleoptera: Elmidae: Elminae) from Colombia: illustrating taxonomical keys Gonzalez Córdoba, Marcela; Zuñiga, Marıa del Carmen; Manzo, María Verónica; Giraldo, Lina Paola; Chará, Julián Material de los géneros Notelmis Hinton y Onychelmis Hinton de diferentes localidades de Colombia es analizado. Se registran por primera vez para el país dos especies de Notelmis (N. bifoveolata y N. nodipes) y una de Onychelmis (O. leleupi), conocidas para Ecuador, Panamá y Costa Rica y se amplían los rangos de distribución de estos géneros y la especie O. longicollis. Estos taxones se ubican principalmente en la región natural andina en un rango altitudinal comprendido entre 96 y 2700 msnm. Se complementa la información con claves taxonómicas ilustradas para la separación e identificación de las especies registradas en Colombia hasta el momento, mapas de distribución a nivel genérico y específico y datos ecológicos de las localidades de colecta.; Material belonging to the genus Notelmis Hinton y Onychelmis Hinton from different localities from Colombia are evaluated. Two species of Notelmis (N. bifoveolata and N. nodipes) and one of Onychelmis (O. leleupi) are recorded in this country for the first time. The species have been previously found in Ecuador, Panama and Costa Rica. The distribution ranges for the genera Notelmis, Onychelmis, and for the species O. longicollis are also expanded for Colombia. Specimens are mainly located in the Andean natural region between altitudes of 96 and 2,700 meters above sea level. The information is supplemented with illustrated taxonomic keys for identification of the species, distribution maps, and ecological data for the sampling locations.

Mitigation of pulse-width-modulation distortion using a digital predistorter based on memory polynomials Chierchie, Fernando; Cousseau, Juan Edmundo; Paolini, Eduardo Emilio; Stefan Werner This paper presents an adaptive digital predistorter (DPD) that significantly reduces the baseband distortion of digital pulse width modulation (PWM), typically used in switching (class-D) amplifiers. A generalized Hammerstein structure (also known as power filter) composed by static nonlinearities and FIR filters is used to model the baseband behavior of PWM. We show that the contribution of the higher order terms of the nonlinearity are negligible and therefore, for practical applications, only the first three or four odd powers should be retained. The convergence of the DPD is studied and the performance is demonstrated and compared with other approaches. Good results are obtained for typical signals even when using low-order FIR filters in the DPD. Measurement results obtained using a digital signal processor are also presented aiming to validate the proposed approach.

Approximate solutions to the quantum problem of two opposite charges in a constant magnetic field Ardenghi, Juan Sebastian; Gadella, M.; Negro, J. We consider two particles of equal mass and opposite charge in a plane subject to a perpendicular constant magnetic field. This system is integrable but not superintegrable. From the quantum point of view, the solution is given by two fourth degree Hill differential equations which involve the energy as well as a second constant of motion. There are two solvable approximations in relation to the value of a parameter. Starting from each of these approximations, a consistent perturbation theory can be applied to get approximate values of the energy levels and of the second constant of motion.

Influence of macrophyte integrity on zooplankton habitat preference, emphasizing the released phenolic compounds and chromophoric dissolved organic matter Gutierrez, Marìa Florencia; Mayora, Gisela Paola Macrophyte health status can influence the composition of their exudates causing different effects on zooplankton behavior and distribution in nature. We hypothesize that: (1) the release of phenolic compounds and chromophoric dissolved organic matter (CDOM) depends on macrophyte species and its health status (broken macrophytes: BM, or healthy macrophytes: HM); (2) the repellency effect depends on zooplankton species, macrophyte species and its health status; and (3) higher concentrations of phenolic compounds and CDOM produce a stronger repellency effect. Phenolic compounds and CDOM were analyzed in exudates of BM and HM of Salvinia sp., Eichhornia crassipes, Pistia stratiotes, Azolla sp. and Ludwigia peploides. Through a flow-through experiment, the repellency produced by these exudates was assessed in two copepods (Notodiaptomus conifer and Argyrodiaptomus falcifer) and one cladoceran (Ceriodaphnia dubia). Our hypotheses were partially validated. The quantity of exudated phenolic compounds and CDOM depended on macrophyte species and, to a lesser extent, on the plant health status. The repellency effect was affected by macrophyte and zooplankton species but not by the health status of plants. Only C. dubia and A. falcifer increased their evasion behavior when phenolic compound and CDOM concentrations increased. In brief, the structuring effect of repellent substances depends on different factors. Under a certain threshold concentration, zooplankton behavior might depend on the information associated with the plant odor (e.g., predation risk, structural complexity) more than on the quantity of the released chemical compounds. Above this threshold, evasion would be the only possible option to avoid damaging effects.

Tectonic models for the Patagonian orogenic curve (southernmost Andes): An appraisal based on analog experiments from the Fuegian thrust-fold belt Torres Carbonell, Pablo Juan; Guzman, Cecilia Griselda; Yagupsky, Daniel Leonardo; Dimieri, Luis Vicente Tectonic models for the evolution of the Patagonian orogenic curve were evaluated using analog experiments that considered either a rotational or a non-rotational orogenic backstop, combined with a basement promontory on the foreland cratonic margin. Five different kinematic configurations were used, aiming to evaluate the influence of the Río Chico Arc as a rigid obstacle on the evolution of the Fuegian thrust-fold belt. Rotations, strains and displacement fields obtained from each analog experiment were compared with the structural geology known from the Fuegian thrust-fold belt, in order to appraise the tectonic models that are more consistent with the natural structure. The push of a counterclockwise rotational backstop, combined with the buttressing effect of a foreland promontory, seem of major importance in controlling the final structure and map-view shape of the thrust wedge.

Oldest record of Thinocoridae (Aves, Charadriiformes) from South America; Le plus ancien thinocoridé (Aves, Charadriiformes) d’Amérique du Sud Agnolin, Federico; Tomassini, Rodrigo Leandro; Contreras, Victor Hugo Here we describe an isolated distal end of tarsometatarsus coming from the late Miocene levels of the Loma de Las Tapias Formation (San Juan Province, Argentina). The specimen was identified as a Thinocoridae, and constitutes the oldest record for the clade. It also represents the only Tertiary finding for the family from South America and one of the scarce avian remains reported from central Argentina. This record provides new information on the palaeobiogeography of the clade.; Nous décrivons ici une extrémité distale isolée de tarsométatarse provenant du Miocène terminal de la Formation Loma de Las Tapias (Province de San Juan, Argentine). Le spécimen a été identifié comme un Thinocoridae, et constitue le plus ancien enregistrement de cette famille en Amérique du Sud. Il représente aussi la seule occurrence de thinocoridé dans le Tertiaire d’Amérique du Sud et l’un des rares restes d’oiseaux rapportés du centre de l’Argentine. Cette découverte fournit des informations sur la paléobiogéographie des représentants fossiles de ce clade.

Boundaries of Morphological and Molecular Variation and the Distribution of a Miniaturized Froglet, Brachycephalus nodoterga (Anura: Brachycephalidae) Clemente Carvalho, Rute B. G.; Perez, Sergio Ivan; Tonhatti, Carlos H.; Condez, Thais H.; Sawaya, Ricardo J.; Haddad, Celio F. B.; Dos Reis, Sergio F. Most miniaturized froglets of the genus Brachycephalus occur in isolation in slopes of mountain ranges at elevations varying from 600 to 1,800 m in the Atlantic Forest of eastern Brazil. For organisms such as Bracycephalus with spatially discontinuous distributions, a fundamental task is to determine whether observed patterns of variation are consistent with geographic differentiation among allopatric populations within a single species or are suggestive of a potential species boundary. We address this problem by focusing on continental and island population samples potentially assignable to Brachycephalus nodoterga (Anura: Brachycephalidae) from the perspective of variation in qualitative and quantitative morphological traits and DNA sequences. Population samples from continental and island populations share color characteristics, qualitative traits, and multivariate patterns of variation and covariation in cranial metric traits. Comparative analysis of DNA sequences showed the magnitude of molecular distances between B. nodoterga and Brachycephalus ephippium to be 1 order of magnitude larger than molecular distances within B. nodoterga and B. ephippium. We interpret the combined morphological and molecular evidence to indicate that continental and island population samples examined here are conspecific. Therefore, by defining species boundaries for B. nodoterga, we also established minimal estimates of its distribution.

Marine bacterial community structure resilience to changes in protist predation under phytoplankton bloom conditions Baltar, Federico; Palovaara, Joakim; Unrein, Fernando; Catala, Philippe; Horňák, Karel; Šimek, Karel; Vaqué, Dolors; Massana, Ramon; Gasol, Josep M.; Pinhassi, Jarone To test whether protist grazing selectively affects the composition of aquatic bacterial communities, we combined high-throughput sequencing to determine bacterial community composition with analyses of grazing rates, protist and bacterial abundances and bacterial cell sizes and physiological states in a mesocosm experiment in which nutrients were added to stimulate a phytoplankton bloom. A large variability was observed in the abundances of bacteria (from 0.7 to 2.4 × 10 6 cells per ml), heterotrophic nanoflagellates (from 0.063 to 2.7 × 10 4 cells per ml) and ciliates (from 100 to 3000 cells per l) during the experiment (∼3-, 45- and 30-fold, respectively), as well as in bulk grazing rates (from 1 to 13 × 10 6 bacteria per ml per day) and bacterial production (from 3 to 379 μg per C l per day) (1 and 2 orders of magnitude, respectively). However, these strong changes in predation pressure did not induce comparable responses in bacterial community composition, indicating that bacterial community structure was resilient to changes in protist predation pressure. Overall, our results indicate that peaks in protist predation (at least those associated with phytoplankton blooms) do not necessarily trigger substantial changes in the composition of coastal marine bacterioplankton communities.

dsRNA-protein interactions studied by molecular dynamics techniques. Unravelling dsRNA recognition by DCL1 Drusin, Salvador Iván; Suarez, Irina Paula; Gauto, Diego Fernando; Rasia, Rodolfo Maximiliano; Moreno, Diego Martin Double stranded RNA (dsRNA) participates in several biological processes, where RNA molecules acquire secondary structure inside the cell through base complementarity. The double stranded RNA binding domain (dsRBD) is one of the main protein folds that is able to recognize and bind to dsRNA regions. The N-terminal dsRBD of DCL1 in Arabidopsis thaliana (DCL1-1), in contrast to other studied dsRBDs, lacks a stable structure, behaving as an intrinsically disordered protein. DCL1-1 does however recognize dsRNA by acquiring a canonical fold in the presence of its substrate. Here we present a detailed modeling and molecular dynamics study of dsRNA recognition by DCL1-1. We found that DCL1-1 forms stable complexes with different RNAs and we characterized the residues involved in binding. Although the domain shows a binding loop substantially shorter than other homologs, it can still interact with the dsRNA and results in bending of the dsRNA A-type helix. Furthermore, we found that R8, a non-conserved residue located in the first dsRNA binding region, recognizes preferentially mismatched base pairs. We discuss our findings in the context of the function of DCL1-1 within the microRNA processing complex.

Cambios morfológicos producidos por el Parasitismo de Strelkovimermis Spiculatus Poinar & Camino, 1986 (Nematoda, Mermithidae): En larvas del mosquito Culex Pipiens Linneaus, 1758 (Diptera, Culicidae); Morphological changes caused by parasitism of Strelkovimermis spiculatus (Nematoda, Mermithidae) in Culex Pipiens mosquito larvae (Diptera, Culicidae) Reboredo, Guillermo Raul; González, Sandra Elizabeth; Rusconi, José Matías; Camino, Nora Beatriz El presente estudio evalúa el efecto del parasitismo de Strelkovimermis spiculatus Poinar & Camino, 1986 (Nematoda, Mermithidae), sobre larvas del mosquito Culex pipiens Linnaeus, 1758 (Diptera, Culicidae) a nivel histopatológico. Debido a la presencia del nemátodo que se evidencia por sus estructuras tales como los homorocitos, esticocitos, cuerdas longitudinales y trofosoma, se observó una alteración principalmente a nivel del epitelio intestinal, el cuerpo graso y la musculatura de la larva.; This study reports the effect of parasitism of the mermithid Strelkovimermis spiculatus Poinar & Camino, 1986 (Nematoda, Mermithidae)parasitizing larvae of the mosquito Culex pipiens Linneaus, 1758 (Diptera, Culicidae) at histopathological level. Due to the presence of nematode,evidenced by their structures such as longitudinal chords and trophosome, we observed changes mainly at the intestinal epithelium, fat body andmuscle of the larva.

Sentidos sobre la política en las memorias sobre la toma de la Escuela de Educación Técnica Nº 1 de Bahía Blanca en 1973 Seitz, Ana Inés El artículo aborda las memorias de exalumnos de la Escuela de Educación Técnica N° 1 de Bahía Blanca sobre la toma del colegio en junio de 1973, a pocos días de la asunción de Héctor Cámpora como presidente. En estos relatos es posible reconocer dos grupos distintos. Por un lado, el de quienes enfatizan el carácter apolítico de la medida, fundando la acción en reclamos exclusivamente gremiales. Por el otro, el de aquellos que, por el contrario, señalan que la ocupación de la escuela fue generada por la injerencia de sectores del peronismo de izquierda local. A través del análisis de las memorias de estos exestudiantes sobre el proceso de ocupación del colegio en 1973, este trabajo se propone indagar en los sentidos que la política y la militancia política adquieren para ellos en el presente.

FARGO3D: A new GPU-oriented MHD code Benítez Llambay, Pablo; Masset, Frédéric S. We present the FARGO3D code, recently publicly released. It is a magnetohydrodynamics code developed with special emphasis on the physics of protoplanetary disks and planet-disk interactions, and parallelized with MPI. The hydrodynamics algorithms are based on finite-difference upwind, dimensionally split methods. The magnetohydrodynamics algorithms consist of the constrained transport method to preserve the divergence-free property of the magnetic field to machine accuracy, coupled to a method of characteristics for the evaluation of electromotive forces and Lorentz forces. Orbital advection is implemented, and an N-body solver is included to simulate planets or stars interacting with the gas. We present our implementation in detail and present a number of widely known tests for comparison purposes. One strength of FARGO3D is that it can run on either graphical processing units (GPUs) or central processing units (CPUs), achieving large speed-up with respect to CPU cores. We describe our implementation choices, which allow a user with no prior knowledge of GPU programming to develop new routines for CPUs, and have them translated automatically for GPUs.

Rab GTPases and the Autophagy Pathway: Bacterial Targets for a Suitable Biogenesis and Trafficking of Their Own Vacuoles Lopez de Armentia, María Milagros; Amaya, Celina; Colombo, Maria Isabel Autophagy is an intracellular process that comprises degradation of damaged organelles, protein aggregates and intracellular pathogens, having an important role in controlling the fate of invading microorganisms. Intracellular pathogens are internalized by professional and non-professional phagocytes, localizing in compartments called phagosomes. To degrade the internalized microorganism, the microbial phagosome matures by fusion events with early and late endosomal compartments and lysosomes, a process that is regulated by Rab GTPases. Interestingly, in order to survive and replicate in the phagosome, some pathogens employ different strategies to manipulate vesicular traffic, inhibiting phagolysosomal biogenesis (e.g., Staphylococcus aureus and Mycobacterium tuberculosis) or surviving in acidic compartments and forming replicative vacuoles (e.g., Coxiella burnetti and Legionella pneumophila). The bacteria described in this review often use secretion systems to control the host?s response and thus disseminate. To date, eight types of secretion systems (Type I to Type VIII) are known. Some of these systems are used by bacteria to translocate pathogenic proteins into the host cell and regulate replicative vacuole formation, apoptosis, cytokine responses, and autophagy. Herein, we have focused on how bacteria manipulate small Rab GTPases to control many of these processes. The growing knowledge in this field may facilitate the development of new treatments or contribute to the prevention of these types of bacterial infections.

Early short-term treatment with neutralizing human monoclonal antibodies halts SHIV infection in infant macaques Hessell, Ann J.; Jaworski, Juan Pablo; Epson, Erin; Matsuda, Kenta; Pandey, Shilpi; Kahl, Christoph; Reed, Jason; Sutton, William F.; Hammond, Katherine B.; Cheever, Tracy A.; Barnette, Philip T.; Legasse, Alfred W.; Planer, Shannon; Stanton, Jeffrey J.; Pegu, Amarendra; Chen, Xuejun; Wang, Keyun; Siess, Don; Burke, David; Park, Byung S.; Axthelm, Michael K; Lewis, Anne; Hirsch, Vanessa M.; Graham, Barney S.; Mascola, John R.; Sacha, Jonah B.; Haigwood, Nancy L. Prevention of mother-to-child transmission (MTCT) of HIV remains a major objective where antenatal care is not readily accessible. We tested HIV-1–specific human neutralizing monoclonal antibodies (NmAbs) as a post-exposure therapy in an infant macaque model for intrapartum MTCT. One-month-old rhesus macaques were inoculated orally with the simian-human immunodeficiency virus SHIVSF162P3. On days 1, 4, 7 and 10 after virus exposure, we injected animals subcutaneously with NmAbs and quantified systemic distribution of NmAbs in multiple tissues within 24 h after antibody administration. Replicating virus was found in multiple tissues by day 1 in animals that were not treated. All NmAb-treated macaques were free of virus in blood and tissues at 6 months after exposure. We detected no anti-SHIV T cell responses in blood or tissues at necropsy, and no virus emerged after CD8+ T cell depletion. These results suggest that early passive immunotherapy can eliminate early viral foci and thereby prevent the establishment of viral reservoirs.

Acerca de los inicios de la divulgación del Psicoanálisis en Argentina: un análisis de escuela para padres; About the beginning of the popularization og Psychoanalysis in Argentina: an analysis of school for parents Savio, Ana Karina En este artículo nos proponemos analizar los tres tomos de Escuela para Padres de Eva Giberti. Buscamos, por un lado, reflexionar sobre el dispositivo enunciativo que allí surge (Maingueneau, 1987, 1999; Amossy, 2005) y, por el otro, rastrear el modo o los modos en que se construye, formula y reformula el saber experto en estos textos (Authier, 1993, 1995). El trabajo ha revelado que la divulgadora/enunciadora no se presenta como una simple mediadora entre el público lector y el saber del experto, sino que, por el contrario, las imágenes que se construyen en torno a su figura y al vínculo con el enunciatario presentan distintos matices y generan diversos efectos de sentido en el entramado discursivo. Por otra parte, se ha advertido que el nuevo saber al que se refieren no se manifiesta como inalcanzable o cerrado a la comunidad psicoanalítica.; In this article, we analyze the three volumes titled Escuela para Padres, written by Eva Giberti. We seek, on the one hand, reflect on the enunciative device (Maingueneau, 1987, 1999; Amossy, 2005) and, on the other, consider the mode or the modes in which it is constructed, formulate and reformulate the expert knowledge in these texts (Authier, 1993, 1995). This study has identified that in these texts the enunciator is not presented as a simple mediator between the public readers and the expert knowledge, but, on the contrary, the images that are constructed around its figure and the relation with the addresses have different nuances and generate various sense effects in the discursive framework. On the other hand, it has concluded that the new knowledge they refer to does not appear as out of reach, closed to the psychoanalytic community.

Nanotoxicological Effects of SiO2 Nanoparticles on Spodoptera frugiperda Sf9 Cells Santo Orihuela, Pablo Luis; Foglia, María Lucía; Targovnik, Alexandra Marisa; Miranda, Maria Victoria; Desimone, Martín Federico The application of silica nanoparticles (NPs) in the biomedical field experienced a great development. Thedriving forces for these and future developments are the possibility to design NPs with homogeneous size and structureamenable to specific grafting. Moreover, it is possible to tune the characteristics of the NPs to meet the requirements ofeach specific cell and desired application. Herein, we analyzed the effect of silica NPs of various sizes and surface chargeon the viability of Spodoptera frugiperda cells (Sf9 cell line) with the aim of extending the knowledge of possible toxicityof the NPs in the environment and development of new tools for insect control. Moreover, these results will also contributeto develop more effective systems for gene vectors delivery and recombinant proteins expression. Bare silica NPs of14 nm, 380 nm and 1430 nm as well as amine-modified silica NPs of 131 nm and 448 nm were obtained by the Stöbermethod. The NPs were characterized by DLS and zeta potential measurements. The cell viability was assessed by theMTT test. It was observed that the 14 nm NPs possess the highest toxic effect. Indeed, after 24h, the viability of the cellsexposed to the lower concentration of NPs (0.12 mg/ml) was about 40% of the value obtained for the control cells not exposedto NPs. Moreover, the exposure to other negative charged NPs also causes a lower activity when compared with thecontrol. Alternatively, lower concentrations of positive charged NPs (i.e.: 0.12 or 0.6 mg/ml) demonstrated to stimulatethe proliferation of the cells and higher concentrations (i.e.: 7.2 mg/ml) did not present significant differences with thecontrol. In conclusion, we have demonstrated that the NPs possess an effect that is highly influenced by the size, chargeand concentration. Although, silica NPs are being used in the biomedical field, these results contribute to further understandingthe risk that could be associated to nanoparticles and how these can be modified in order to meet the requirementsof each desired application.

First Steps in the Aggregation Process of Copolymers Based on Thymine Monomers: Characterization by Molecular Dynamics Simulations and Atomic Force Microscopy Garay, Alberto Sergio; Rodrigues, Daniel Enrique; Fuselli, Antonela; Martino, Debora Marcela; Passeggi, Mario Cesar Guillermo Atomistic molecular dynamic simulations were performed to study thestructure of isolated VBT−VBA (vinylbenzylthymine−vinylbenzyltriethylammoniumchloride) copolymer chains in water at different monomeric species ratios (1:1 and 1:4).The geometric parameters of the structure that the copolymers form in equilibrium together with the basic interactions that stabilize them were determined. Atomic force microscopy (AFM) measurements of dried diluted concentrations of the two copolymers onto highly oriented pyrolytic graphite (HOPG) substrates were carried out to study their aggregation arrangement. The experiments show that both copolymers arrange in fiber-like structures. Comparing the diameters predicted by the simulation results and those obtainedby AFM, it can be concluded that individual copolymers arrange in bunches of two chains, stabilized by contra-ions−copolymer interactions for the 1:1 copolymerization ratio at the ionic strength of our samples. In contrast, for the 1:4 system the individual copolymer chains do not aggregate in bunches. These results remark the relevance of the copolymerization ratio and ionic strength of the solvent in the mesoscopic structure of these materials.

Rheological behavior of concentrated skim milk dispersions as affected by physicochemical conditions: change in pH and CaCl2 addition Olivares, María Laura; Achkar, Natalia Patricia; Zorrilla, Susana Understanding the behavior of casein micelles (CM) in concentrated regimes is critical for the design of dairy unit operations such as drying or evaporation but also it is still scarce. In this work, the effect of the decrease in pH and the addition of a calcium salt on concentrated skim milk dispersions was examined by rheometric measurements at 25 °C. Control samples (S1), samples with a pH of 5.8 (S2), and samples with 0.04 M CaCl2 addition (S3) at different concentrations (40, 45, 48, 50, and 52% w/w) were analyzed through flow curves and oscillatory dynamic data by frequency sweep tests. All samples showed a clear shear thinning non-Newtonian behavior and a large dependence on concentration, dispersions being more fluid for samples S2 and S3. A viscosity model for microgels was used to obtain parameters related to the characteristic structure of systems. It was demonstrated that CM had a similar structure for the different physicochemical systems studied and that the decrease of pH and the addition of salt reduced the dispersion stability due to electrostatic and steric potential energy is depleted. Dynamic data showed that dispersions at the highest concentration had dominant and similar elastic behavior and weak gel character. A transition regime from fluid to gel was observed in samples S2 at 45% w/w. No samples obeyed the Cox-Merz rule. This study allowed gaining more understanding related to the structure of CM systems studied.