Mathematical Modeling of Hydrogels Swelling Based on the Finite Element Method

In recent years, hydrogels have been introduced as new materials suitable for applications in areas such as biomedical engineering, agriculture, etc. The rate and degree of hydrogel swelling are important parameters that control the diffusion of drugs or solvents inside a polymer network. Therefore, the description of the dynamic swelling process of the hydrogels is very important in applications that require precise control of the absorption of solvents inside the hydrogel structure. To date, most of the numerical models developed for describing the swelling process are based in the finite difference methods. Even though numerical models supported in finite differences can be easily implemented, their use is limited to samples with very simple shapes. In this paper, a new model based on the finite element method is proposed. The diffusion equation is solved in a time-deformable grid. An original procedure is proposed to numerically solve the non-linear algebraic equation system that permits computing a new grid for each time-step. Hydrogel samples of different shapes were prepared in order to conduct experimental tests to validate the numerical proposed model. Numerical results show that the new model is able to describe the mass and shape changes in the hydrogel samples in time. An application of the numerical model to determine the relation between diffusion coefficients and density in Poly-acrylamide samples allows verifying the versatility of the model.

Quantitative Electrophilicity Measures

Quantitative correlation of several theoretical electrophilicity measures over different families of organic compounds are examined relative to the experimental values of Mayr et al.Notably,the ability to predict these values accurately will help to elucidate the reactivity and selectivity trends observed in charge-transfer reactions.A crucial advantage of this theoretical approach is that itprovides this information without the need of experiments,which are often demanding and time-consuming.Here,two different types of electrophilicity measures were analyzed.First,models derived from conceptual density functional theory(c-DFT),including Parr's original proposal and further generalizations of this index,are investigated.For instance,the approaches of Gázquez et al.and Chamorro et al.are considered,whereby it is possible to distinguish between processes in which a molecule gains or loses electrons.Further,we also explored two novel electrophilicity definitions.On one hand,the potential of environmental perturbations to affect electron incorporation into a system is analyzed in terms of recent developments in c-DFT.These studies highlight the importance of considering the molecular surroundings when a consistent description of chemical reactivity is needed.On the other hand,we test a new definition of electrophilicity that is free from inconsistencies(so-called thermodynamic electrophilicity).This approach is based on Parr's pioneering insights,though it corrects issues present in the standard working expression for the calculation of electrophilicity.Additionally,we use machine-learning tools(i.e.,symbolic regression) to identify the models that best fit the experimental values.In this way,the best possible description of the electrophilicity values in terms of different electronic structure quantities is obtained.Overall,this straightforward approach enables one to obtain good correlations between the theoretical and experimental quantities by using the simple,yet powerful,interpretative advantage of c-DFT methods.In general,we observed that the correlations found at the HF/6-31 G(d) level of theory are of semi-quantitative value.To obtain more accurate results,we showed that working with families of compounds with similar functional groups is indispensable.

The role of surface functionalization of silica nanoparticles for bioimaging

Among the several types of inorganic nanoparticles available,silica nanoparticles(SNP)have earned their relevance in biological applications namely,as bioimaging agents.In fact,uorescent SNP(FSNP)have been explored in this-eld as protective nanocarriers,overcoming some limitations presented by conventional organic dyes such as high photobleaching rates.A crucial aspect on the use of uorescent SNP relates to their surface properties,since it determines the extent of interaction between nanoparticles and biological systems,namely in terms of colloidal stability in water,cellular recognition and internalization,tracking,biodistribution and speci-city,among others.Therefore,it is imperative to understand the mechanisms underlying the interaction between biosystems and the SNP surfaces,making surface functionalization a relevant step in order to take full advantage of particle properties.The versatility of the surface chemistry on silica platforms,together with the intrinsic hydrophilicity and biocompatibility,make these systems suitable for bioimaging applications,such as those mentioned in this review.

Review of Brazilian Activities Related to the Thorium Fuel Cycle and Production of Thorium Compounds at IPEN-CNEN/SP

The Brazilian＇s interest in the nuclear utilization of thorium has started in the 1950s as a consequence of the abundant occurrence ofmonazite sands. Since the 1960s, IPEN-CNEN/SP （lnstituto de Pesquisas Energ6ticas e Nucleares） has performed some developments related to the thorium fuel cycle. The production and purification of thorium compounds was carried out at IPEN for about 18 years and the main product was the thorium nitrate with high purity, having been produced over 170 metric tons of this material in the period, obtained through solvent extraction. The thorium nitrate was supplied to the domestic industry and used for gas portable lamps （Welsbach mantle）. Although the thorium compounds produced have not been employed in the nuclear area, several studies were conducted. Therefore, those activities and the accumulated experience are of strategic importance, on one hand, due to huge Brazilian thorium reserves, on the other hand, by the resurgence of the interest of thorium for the Generation IV advanced reactors. This paper presents a review of the Brazilian research and development activities related to thorium technology.

Recent therapeutic applications of the theranostic principle with dendrimers in oncology

At the intersection between treatment and diagnosis, nanoparticles technologies are strongly impacting the development of both therapeutic and diagnostic agents.Consequently, the development of novel modalities for concomitant noninvasive therapy and diagnostics known as theranostics as a single platform has gained significant interests. These multifunctional theranostic platforms include carbon-based nanomaterials（e.g., carbon nanotubes）, drug conjugates, aliphatic polymers, micelles, vesicles, core-shell nanoparticles, microbubbles and dendrimers bearing different contrast agents and drugs, such as cytotoxic compounds in the oncology domain. Dendrimers emerged as a new class of highly tunable hyperbranched polymers, and have been developed as useful theranostic platforms. Magnetic resonance imaging, gamma scintigraphy, computed tomography and optical imaging are the main techniques developed with dendrimers in the theranostic domain in oncology. Different imaging agents have been used such as Gd（Ⅲ）,19F, Fe2O3（MRI）,76Br（PET）,111In,88Y,153Gd,188Re,131I（SPECT）,177Lu,gold（CT） and boronated groups, siliconnaphthalocyanines,dialkylcarbocyanines and QDs（optical imaging dyes）.

Characterization of atmospheric aerosol (PM10 and PM2.5) from a medium sized city in S?o Paulo state,Brazil

Air pollution causes deleterious effects on human health with aerosols being among the most polluting agents.The objective of this work is the characterization of the PM2.5 and PM10 aerosol mass in the atmosphere.The methods of analysis include WD-XRF and EDS.Data were correlated with meteorological information and air mass trajectories(model HYSPLIT)by multivariate analysis.A morphological structural analysis was also carried out to identify the probable sources of atmospheric aerosols in the city of Sao Jose do Rio Preto,Brazil.The mean mass concentration values obtained were 24.54 μg/m^3 for PM10,above the WHO annual standard value of 20 μg/m^3 and 10.88 μg/m^3 for PM2.5 whose WHO recommended limit is10 μg/m^3.WD-XRF analysis of the samples revealed Si and Al as major components of the coarse fraction.In the fine fraction,the major elements were Al and S.The SEM-FEG characterization allowed identifying the morphology of the particles in agglomerates,ellipsoids and filaments in the PM10,besides spherical in the PM2.5.The analysis by EDS corroborated WD-XRF results,identifying the crustal elements,aluminosilicates and elements of anthropogenic origin in the coarse fraction.For the fine fraction crustal elements were also identified;aluminosilicates,black carbon and spherical particles(C and O) originating from combustion processes were predominant.The use of multivariate analysis to correlate air mass trajectories with the results of the morpho-structural characterization of the particulate matter allowed confirmation of the complex composition of the particles resulting from the combination of both local and long-distance sources.

An egg-shell bifunctional CeO_(2)-modified NiPd/Al_(2) O_(3) catalyst for petrochemical processes involving selective hydrogenation and hydroisomerization

The catalytic performance during the 1-butyne hydrogenation using two reduced Al_(2) O_(3)-supported Pdbased catalysts was carried out in a total recirculation system with an external fixed-bed reactor.The lab-prepared egg-shell NiPd/CeO_(2)-Al_(2) O_(3) catalyst(NiPdCe) with Pd loading=0.5 wt%,Ni/Pd atomic ratio=1 and CeO_(2) loading=3 wt% was synthesized and characterized,and it was compared with an egg-shell Al_(2) O_(3)-supported Pd based commercial catalyst(PdCC).The reduced catalysts were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,and high-resolution transmission electron microscopy.The textural characteristics and ammonia temperature-programmed desorption profiles of the fresh(unreduced) catalysts were also obtained.Both catalysts show high 1-butyne conversion and selectivity to 1-butene,but the catalysts also present important differences between hydroisomerizing and hydrogenating capabilities.NiPdCe catalyst shows higher capability for hydroisomerization reactions,while the PdCC catalyst exhibits higher hydrogenating capability.The observed catalytic performances can be interesting for some industrial processes and can provide a guideline for the development of a Pd-based catalyst with specific catalytic properties.

Titanate Nanorods Modified with Nanocrystalline ZnS Particles and Their Photocatalytic Activity on Pollutant Removal

Aiming to produce materials with enhanced photocatalytic properties, the synthesis of new crystalline nanocomposites by combining titanate nanorods（TNR） with ZnS nanocrystallites is described in this work.The TNR modification was accomplished by an in situ nucleation and growth process of ZnS nanoparticles.Zinc diethyldithiocarbamate was used as the metal chalcogenide precursor. The prepared materials were structural, morphological and optical characterized by X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy, energy dispersive spectroscopy and powder diffuse reflectance spectra. Crystalline Zn S nanoparticles were obtained as a homogeneous and continuous layer, covering completely the TNR surface. The application of these new nanocomposite materials on photocatalytic degradation of pollutants was investigated. First, the evaluation of hydroxyl radical formation, using the terephthalic acid as probe, was studied. Afterwards, the adsorption and photodegradation of safranine-T, used here as a model pollutant molecule, was investigated. The obtained data indicate that the prepared nanocomposites have potential to be used as photocatalysts for organic pollutant removal.The best removal results（97% removal） were obtained using the 0.01 Zn S/HTNR sample as catalyst（0.2 g/L; 10 ppm safranin-T solution） with a combination of a low dye adsorption（20%） and a high dye photocatalytic degradation（77%）.