Applications of Plasma-Activated Water in Dentistry: A Review

The activation of water by non-thermal plasma creates a liquid with active constituents referred to as plasma-activated water (PAW). Due to its active constituents, PAW may play an important role in different fields, such as agriculture, the food industry and healthcare. Plasma liquid technology has received attention in recent years due to its versatility and good potential, mainly focused on different health care purposes. This interest has extended to dentistry, since the use of a plasma–liquid technology could bring clinical advantages, compared to direct application of non-thermal atmospheric pressure plasmas (NTAPPs). The aim of this paper is to discuss the applicability of PAW in different areas of dentistry, according to the published literature about NTAPPs and plasma–liquid technology. The direct and indirect application of NTAPPs are presented in the introduction. Posteriorly, the main reactors for generating PAW and its active constituents with a role in biomedical applications are specified, followed by a section that discusses, in detail, the use of PAW as a tool for different oral diseases.     

Composite with Recyclable Loads for the Manufacture of Blocks to Build Popular Houses

The science space in a state school in Natal city was built using a composite consisting of gypsum, EPS （expanded polystyrene）, shredded tire, cement and water. Mechanical and thermal resistances were evaluated. Inside the blocks, three types of fillings （EPS plates, aluminum cans and 500 mL bottles of mineral water） were placed in order to obtain a walls with higher thermal resistance, but also to give it an ecologically correct order, considering that both the tire and the EPS occupy a large space in landfills and require years to be degraded when released into the environment. Compression tests were conducted according to the rules. The experiments demonstrated that the temperature difference between the internal and external surfaces on the walls reached levels above 12.0 ℃. It was also demonstrated that the proposed composite has adequate mechanical strength to be used for sealing walls. The proposed use of the composite can contribute to reduce the significant housing deficit of Brazil, producing popular houses at low cost and with little time to work.     

High-entropy oxides: Harnessing crystalline disorder for emergent functionality

High-entropy materials defy historical materials design paradigms by leveraging chemical disorder to kinetically stabilize novel crystalline solid solutions comprised of many end-members. Formulational diversity results in local crystal structures that are seldom found in conventional materials and can strongly influence macroscopic physical properties. Thermodynamically prescribed chemical flexibility provides a means to tune such properties. Additionally, kinetic metastability results in many possible atomic arrangements, including both solid-solution configurations and heterogeneous phase assemblies, depending on synthesis conditions. Local disorder induced by metastability, and extensive cation solubilities allowed by thermodynamics combine to give many high-entropy oxide systems utility as electrochemical, magnetic, thermal, dielectric, and optical materials. Though high-entropy materials research is maturing rapidly, much remains to be understood and many compositions still await discovery, exploration, and implementation.     

Monitoring pH-dependent conformational changes in aqueous solutions of poly(methacrylic acid)-b-polydimethylsiloxane copolymer based on fluorescence spectra of pyrene and 1,3-bis(1-pyrenyl)propane

Aqueous solutions of poly(methacrylic acid)-b-polydimethylsiloxane copolymer (PMA-b-PDMS), and reference solutions of PMA homopolymer, were studied as a function of pH using fluorescent probes: pyrene (P) and 1,3-bis(1-pyrenyl)propane (P3P). In both polymers the conformational transition of PMA chains at pH>5 was reflected in the sharp increase of the intensity ratio of the first to the third vibronic band in emission spectra of P; an excimer emission appeared for P3P, as well as for P if the probe concentration was higher than its solubility limit in water. The excimer to monomer intensity ratio of both probes is a sensitive indicator of the conformational transitions of polymer chains, but P3P is significantly more sensitive compared to pyrene. The data clearly indicated that the presence of PDMS blocks markedly facilitated the transition, even though the ratio of dimethylsiloxane to methacrylic acid units in the copolymer was low, 1:34. The absence of the P3P excimer emission at pH≈3 was rationalized by assuming that clustering of sections of PMA chains around pyrene moieties imposes an extended conformation of the probe molecule.     

Electrochemical behavior of the Ti–6Al–4V alloy coated with a-C:H films

In this work diamond-like carbon films were deposited on the Ti–6Al–4V alloy, which has been used in aeronautics and biomedical fields, by electrical discharges using a magnetron cathode and a 99.999% graphite target in two different atmospheres, the first one constituted by argon and hydrogen and the second one by argon and methane. Films deposited using the argon/hydrogen mixture were called a-C:H, while films deposited using the argon/methane mixture were called DLC. Raman spectroscopy was used to study the structure of the films. The Raman spectra profile of the a-C:H films is quite different from that of the DLC films. The disorder degree of the graphite crystalline phase in a-C:H films is higher than in DLC films (a-C:H films present small values for the the I_D/I_G ratio). Potentiodynamic corrosion tests in 0.5 mol l⁻¹ NaCl aqueous solution, pH 5.8, at room temperature (≈25 °C) were carried out as for the a-C:H as for the DLC coated surfaces. Comparison between the corrosion parameters of a-C:H and DLC coated surfaces under similar deposition time, showed that DLC coated surfaces present bigger corrosion potential (E_corr) and polarization resistance than those coated with a-C:H films. Electrochemical impedance spectroscopy (EIS) was also used to study the electrochemical behavior of a-C:H and DLC coated surfaces exposed to 0.5 mol l⁻¹ aqueous solution. The EIS results were simulated with equivalent electrical circuit models for porous films. The results of these simulations showed similar tendency to the one observed in the potentiodynamic corrosion tests. The DLC film resistance and the charge transfer resistance (R_ct) for the DLC coated surface/electrolyte interface were bigger than the ones determined for the a-C:H coated surfaces.     

Nutritional recovery of mild and moderately malnourished children under two different treatment approaches (ambulatory versus day-care)

This retrospective analysis was conducted between May 1997 and May 2000 at the Centro de Atención Nutricional Infantil de Antímano, CANIA, in Caracas, Venezuela to assess the efficacy of two treatments (ambulatory versus day-care) of mild and moderate malnourished children. Inclusion criteria were: children under 10 years old with mild and moderate malnourishment, who attended a minimum of 3 control visits during a period of 12 months. One hundred fourteen malnourished children were included: fifty seven in ambulatory treatment and fifty seven in day-care treatment paired per nutritional diagnosis, gender and age (thirty nine mild and eighteen moderate malnourished children). The nutritional recovery criterion was weight for height above tenth percentile. No relation was found between treatment approaches and nutritional recovery at 3 and 6 months of treatment. In the group of mild malnourished children, the percentage of recovered patients at 3 months of treatment, that kept their recovered condition at 6 months was 83% (15/18) in the ambulatory treatment and 82% (18/22) in the day-care treatment Age of children, associated disease, acute morbidity, dietetic risk and mother's education and age were not associated with nutritional recovery at 6 months of treatment (p > 0.05). The day-care approach resulted as effective as ambulatory in mild malnourished children. In moderate malnourished new studies will need to be conducted with greater number of patients.     

Ligand Binding Promiscuity of Human Liver Fatty Acid Binding Protein: Structural and Dynamic Insights from an Interaction Study with Glycocholate and Oleate

Human liver fatty acid binding protein (hL‐FABP) has been reported to act as an intracellular shuttle of lipid molecules, thus playing a central role in systemic metabolic homeostasis. The involvement of hL‐FABP in the transport of bile salts has been postulated but scarcely investigated. Here we describe a thorough NMR investigation of glycocholate (GCA) binding to hL‐FABP. The protein molecule bound a single molecule of GCA, in contrast to the 1:2 stoichiometry observed with fatty acids. GCA was found to occupy the large internal cavity of hL‐FABP, without requiring major conformational rearrangement of the protein backbone; rather, this led to increased stability, similar to that estimated for the hL‐FABP:oleate complex. Fast‐timescale dynamics appeared not to be significantly perturbed in the presence of ligands. Slow motions (unlike for other proteins of the family) were retained or enhanced upon binding, consistent with a requirement for structural plasticity for promiscuous recognition.     

On the Determination of the Concentration of Crystal Nuclei in Glasses by DSC

An interesting technique was proposed by Ray et al. over a decade ago to determine the number density of nucleation sites, N_q, or the nucleation rate, I(T), in glasses that exhibit internal nucleation. Their approach is based on the measurement of the areas under the differential scanning calorimetry (DSC) crystallization peaks of partially crystallized glass samples. In this study, we review their method and test a modified equation recently proposed by some of us, which also takes into account the crystal morphology and impingement. We compare N_q obtained with both methods for a Li₂O·2SiO₂ glass. Small glass monoliths were treated at 620°C for different time periods for crystal growth, without any nucleation treatment, and subsequently analyzed by DSC up to 800°C. We thus estimated N_q from the area under the DSC crystallization peaks. The corrected approach resulted in N_q values which were not affected by the pair of growth times chosen, as expected, but the obtained values were two‐ to fivefold lower than those calculated with the Ray model. Taking into account previously reported nucleation rates and the corresponding induction periods as a function of temperature (for specimens of the same glass batch), we estimated the number of nuclei formed during the DSC heating/cooling steps, and also measured them by optical microscopy (OM). Finally, we compared the obtained values from OM with the N_q values determined by the DSC method. The N_q resulting from the original and new equations were approximately two orders of magnitude larger than those experimentally determined for the same glass using optical microscopy. This difference is attributed to the formation of new nuclei during the heating and cooling paths of the DSC runs and to surface crystallization, which are not taken into account in the DSC expressions.     

Robust Simulation of Counterflow Moving Bed Dryers

Abstract

In this work, a robust and accurate strategy for simulating counterflow moving bed dryers is presented. A complete pseudo-transient phenomenological model for the process has been developed and the variable time is used as a continuation parameter. The desired solution is the final steady-state reached by the model. The code DASSL is used to perform the integration of the differential algebraic equation system and consistent initialization is achieved via a direct technique. The computational effort is surprisingly small comparing to those reported in the literature. Reasonable concordance between simulated and experimental results has been observed even though the mathematical model contains no adjustable parameters. Convergence problems have not been observed for all tested operating conditions, including those pointed by other authors as particularly difficult. The mathematical tool built is capable of making accurate predictions about the behavior of the equipment in affordable computing time and hence this constitutes an invaluable tool to study counterflow moving bed drying.     

Up-Regulation of mRNA Ventricular PRNP Prion Protein Gene Expression in Air Pollution Highly Exposed Young Urbanites: Endoplasmic Reticulum Stress,Glucose Regulated Protein 78, and Nanosized Particles

Mexico City Metropolitan Area children and young adults exposed to high concentrations of air pollutants including fine and ultrafine particulate matter (PM) vs. clean air controls, exhibit myocardial inflammation and inflammasome activation with a differential right and left ventricular expression of key inflammatory genes and inflammasomes. We investigated the mRNA expression levels of the prion protein gene PRNP, which plays an important role in the protection against oxidative stress and metal toxicity, and the glucose regulated protein 78, a key protein in endoplasmic reticulum (ER) stress signaling, in ventricular autopsy samples from 30 children and young adults age 19.97 ± 6.8 years with a lifetime of low (n:4) vs. high (n:26) air pollution exposures. Light microscopy and transmission electron microscopy studies were carried out in human ventricles, and electron microscopy studies were also done in 5 young, highly exposed Mexico City dogs. There was significant left ventricular PRNP and bi-ventricular GRP78 mRNA up-regulation in Mexico City young urbanites vs. controls. PRNP up-regulation in the left ventricle was significantly different from the right, p < 0.0001, and there was a strong left ventricular PRNP and GRP78 correlation (p = 0.0005). Marked abnormalities in capillary endothelial cells, numerous nanosized particles in myocardial ER and in abnormal mitochondria characterized the highly exposed ventricles. Early and sustained cardiac ER stress could result in detrimental irreversible consequences in urban children, and while highly complex systems maintain myocardial homeostasis, failure to compensate for chronic myocardial inflammation, oxidative and ER stress, and particles damaging myocardial organelles may prime the development of pathophysiological cardiovascular states in young urbanites. Nanosized PM could play a key cardiac myocyte toxicity role.