Effects of Prior Annealing on the Spark Plasma Sintering of Nanostructured Y2O3 Powders

The effects produced by annealing Y₂O₃ nanopowders on their spark plasma sintering (SPS) behavior are systematically investigated in this work. It is found that the annealed powders display higher sinterability with respect to the as‐received ones. Indeed, the maximum densification level reached from pristine powders is about 97.5%, whereas density decreases when further increasing either the sintering temperature or the dwell time. In contrast, the density of SPS products obtained from pretreated powder monotonically increases with temperature and processing time, thus leading to fully dense materials in 30 min at 1050°C and 60 MPa. Correspondingly, it is found that the annealing treatment markedly inhibits grain coarsening during SPS. Thus, dense translucent samples with grain size below 100 nm can be attained from annealed powders. On the other hand, white‐opaque specimens with significantly coarser microstructures (up to 1‐μm‐sized grains) are obtained when pristine powders are directly processed under the same sintering conditions. Furthermore, it is observed that the annealing treatment of SPS samples in air allows for graphite contamination removal, whereas no improvement in term of light transmittance is produced.     

Mutual Prodrugs of 5-Fluorouracil: From a Classic Chemotherapeutic Agent to Novel Potential Anticancer Drugs

The development of potent antitumor agents with a low toxicological profile against healthy cells is still one of the greatest challenges facing medicinal chemistry. In this context, the “mutual prodrug” approach has emerged as a potential tool to overcome undesirable physicochemical features and mitigate the side effects of approved drugs. Among broad-spectrum chemotherapeutics available for clinical use today, 5-fluorouracil (5-FU) is one of the most representative, also included in the World Health Organization model list of essential medicines. Unfortunately, severe side effects and drug resistance phenomena are still the primary limits and drawbacks in its clinical use. This review describes the progress made over the last ten years in developing 5-FU-based mutual prodrugs to improve the therapeutic profile and achieve targeted delivery to cancer tissues.     

Interaction of inositol phosphate with calcite

The interaction of myo-inositol hexaphosphate with calcite was studied to evaluate the adsorption mechanisms and the electrochemical modifications induced by interaction of a molecule at such a high-charge density. In addition to quantitative information through the construction of adsorption isotherms, FT-IR and Laser Doppler Velocimetry - Photon Correlation Spectroscopy (LDV-PCS) were employed to investigate the nature of the adsorbent-adsorbate bonds and to determine the electrophoretic mobility and size of the particles before and after sorption. The experiments were also run with orthophosphate (Pi) for comparison. The amount of sorbed P increased to reach a plateau at 17.8 mol m^-2 for inositol hexaphosphate (IHP) while for Pi rose 1.4 mol m^-2 but at C_e > 610^-4 M it had a sharp increase reaching 155 mol m^-2. As expected, for Pi, adsorption predominated up Ce 610^-4 M by covering about 20% of total surface. The adsorption occurred at sites that behaved as nucleus of formation of the clustering of Ca- and PO₄-ions with the ending formation of calcium phosphate precipitates at C_e higher than 610^-4 M. The reaction of inositol hexaphosphate with calcite involves, besides adsorption, precipitation of Ca salts and hence calcite dissolution also at the lowest added IHP concentrations, accounting for the large amount retained by calcite. Sorption of IHP on calcite caused aggregation of particles at low concentrations followed by an increase of their negative charge and hence re-dispersion at higher concentrations. These results indicate a great IHP-fixing capacity of calcite that can affect its accumulation in soils and P bioavailability, and a considerable change of calcite electrochemical properties and particle size distribution that can modify aggregate stability.     

More than twenty years of advancements on Frontiers in handwriting recognition

In this paper the results of the research in handwriting/handwritten character recognition in about the last quarter of a century are reported, illustrating the results presented during the International Workshop on Frontiers in Handwriting Recognition (IWFHR) and the International Conference on Frontiers in Handwriting Recognition (ICFHR).     

Is the particle deposition in a cell exposure facility comparable to the lungs? A computer model approach

Abstract

Cell exposure experiments at the air-liquid interface (ALI) are used increasingly as indicators for health effects and for the impact of aerosols on the lung. Thereby the aerosol particles are kept airborne and can deposit on a cell surface area similar to the human respiratory tract (RT). However, geometry and air flow rates of an ALI system deviate considerably from the RT. As the tissue-delivered particle dose to the lungs (TD) can hardly be measured, computer models of particle deposition are used here to mimic both the particle deposition at ALI and in the RT. An ALI exposure setup (VitroCell GmbH) for an airflow rate of 100 cm³ min^?1 is selected, where the particle deposition model has been verified experimentally. For the RT we use the hygroscopic lung deposition model of Ferron et al. (2013 Ferron, G. A., S. Upadhyay, R. Zimmermann, and E. Karg. 2013. Model of the deposition of aerosol particles in the respiratory tract of the rat. II. Hygroscopic particle deposition. J. Aerosol Med. Pulm. Drug Deliv. 26 (2):101–19. doi:10.1089/jamp.2011.0965.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). Model runs are performed for the particle deposition and for the deposited particles per surface area in both the ALI and the RT. The results show that the ALI-deposited mass is 1-2 orders of magnitude higher than in the alveolar region, because the surface area of the lung region is substantially larger. A particle size range from 40 to 450 nm is identified, where the ratio of both the deposition in a lung region and the deposition at the ALI varies by a factor less than two. Mean values for this ratio are 31 and 101 for the tracheo-bronchial and the alveolar region, respectively. The same size range is found for the ratio of the deposited particles per surface area in a lung region and at the ALI. For this range the mean surface deposition at the ALI is 23- and 1575-times larger than in the tracheo-bronchial and the alveolar lung region, respectively. The effect is partly compensated by different flow rate and cell size.

Copyright © 2020 American Association for Aerosol Research     

Peroxidase-catalyzed oxidation of β-carotene in HL-60 cells and in model systems: Involvement of phenoxyl radicals

Recent studies provide extensive evidence for the importance of carotenoids in protecting against oxidative stress associated with a number of diseases. In particular, reactions of carotenoids with phenoxyl radicals generated by peroxidasecatalyzed one-electron metabolism of phenolic compounds may represent an important antioxidant function of carotenoids. To further our understanding of the antioxidant mechanisms of carotenoids, we used in the present work two different phenolic compounds, phenol and a polar homologue of vitamin E (2,2,5,7,8-pentamethyl-6-hydroxychromane, PMC), as representatives of two different types of phenols to study reactions of their respective phenoxyl radicals with carotenoids in cells and in model systems. We found that phenoxyl radicals of PMC did not oxidize β-carotene in either HL-60 cells or in model systems with horseradish peroxidase (HRP)/H₂O₂. In contrast, the phenoxyl radicals generated from phenol (by native myeloperoxidase in HL-60 cells or HRP/H₂O₂ in model systems) effectively oxidized β-carotene and other carotenoids (canthaxanthin, lutein, lycopene). One-electron reduction of the phenoxyl radical by ascorbate (assayed by electron spin resonance-detectable formation of semidehydroascorbyl radicals) prevented HRP/H₂O₂-induced oxidation of β-carotene. PMC, but not phenol, protected β-carotene against oxidation induced by a lipid-soluble azo-initiator of peroxyl radicals. No adducts of peroxidase/phenol/H₂O₂-induced β-carotene oxidation intermediates with phenol were detected by high-performance liquid chromatography-mass spectrometry analysis of the reaction mixture. Since carotenoids are essential constituents of the antioxidant defenses in cells and biological fluids, their depletion through the reaction with phenoxyl radicals formed from endogenous, nutritional and environmental phenolics, as well as phenolic drugs, may be an important factor in the development of oxidative stress.     

Using visual and text features for direct marketing on multimedia messaging services domain

Traditionally, direct marketing companies have relied on pre-testing to select the best offers to send to their audience. Companies systematically dispatch the offers under consideration to a limited sample of potential buyers, rank them with respect to their performance and, based on this ranking, decide which offers to send to the wider population. Though this pre-testing process is simple and widely used, recently the industry has been under increased pressure to further optimize learning, in particular when facing severe time and learning space constraints. The main contribution of the present work is to demonstrate that direct marketing firms can exploit the information on visual content to optimize the learning phase. This paper proposes a two-phase learning strategy based on a cascade of regression methods that takes advantage of the visual and text features to improve and accelerate the learning process. Experiments in the domain of a commercial Multimedia Messaging Service (MMS) show the effectiveness of the proposed methods and a significant improvement over traditional learning techniques. The proposed approach can be used in any multimedia direct marketing domain in which offers comprise both a visual and text component.

Ion Channels and Electroosmosis in Porous Geopolymers: A Novel Category of Low-Cost Memristors

Memristors are electric components that emulate the memory and computational properties of biological synapses by remembering the current that flows through them. Here, for the first time, the memristive properties of geopolymers, inexpensive ceramic materials manufactured at room temperature from alkaline activation of amorphous aluminosilicate precursors, are presented. It is demonstrated that geopolymers present all the fingerprints of memristors, and a physics-based model is proposed, which demonstrates that electroosmosis in the bulk geopolymer pores induces ion channels that foster change in the overall conductance of the bulk material, contributing to the observed memristive behavior. This model opens the door to a new category of porous electroosmosis-based bulk memristors. Synaptic functions such as short-term plasticity and long-term plasticity, as well as endurance and retention capabilities are also demonstrated. The reported findings pave the way to the use of geopolymers for low-cost applications in neuromorphic computing.     

Airtightness Testing of Two-?and Three-Unit Buildings with a Single Fan

This paper presents a method for the field measurement of airtightness for two-?and three-unit buildings using only one fan pressurization system, commonly referred to as a blower door. The main advantage of this single-fan method is its lower equipment and labor cost as compared with multiple-fan methods. Results from consecutive tests in the individual units are used to prepare a set of simultaneous equations for airflow, allowing for the calculation of the air leakage characteristics of both the interior partitions and the exterior envelope on a unit-per-unit basis. Tests were performed on four buildings using the single-fan method and were compared with those obtained with a two-fan method. Test results indicate that the single-fan method may be of value as an inexpensive method of estimating the airtightness of two-?and three-unit residential buildings.