The coating of a plate withdrawn from a bath of a suspension of non-Brownian, monodisperse and neutrally buoyant spherical particles suspended in a Newtonian liquid has been studied. Using laser profilometry, particle tracking and local sample weighing we have quantified the thickness $h$ and the particle content of the film for various particle diameters $d$ and volume fractions ($0.10\leqslant \unicode[STIX]{x1D719}\leqslant 0.50$). Three coating regimes have been observed as the withdrawal velocity is increased: (i) no particle entrainment ($h\lesssim d$), (ii) a monolayer of particles ($h\sim d$), and (iii) a thick film ($h\gtrsim d$), where the suspension behaves as an effective viscous fluid following the Landau–Levich–Derjaguin law. We discuss the boundaries between these regimes, as well as the evolution of the liquid and solid content of the coating over the whole range of withdrawal capillary number and volume fractions.

Geopolymers are created by mixing a source of aluminosilicates, which can be natural or by-products from other industries, with an alkaline solution. These materials based on by-products from other industries have proven to be a less polluting alternative for concrete production than ordinary Portland cement (OPC). Geopolymers offer many advantages over OPC, such as excellent mechanical strength, increased durability, thermal resistance, and excellent stability in acidic and alkaline environments. Within these properties, mechanical strength, more specifically compressive strength, is the most important property for analyzing geopolymers as a construction material. For this reason, this study compiled information on the different variables that affect the compressive strength of geopolymers, such as Si/Al ratio, curing temperature and time, type and concentration of alkaline activator, water content, and the effect of impurities. From the information collected, it can be mentioned that geopolymers with Si/Al ratios between 1.5 and 2.0 obtained the highest compressive strengths for the different cases. On the other hand, high moderate temperatures (between 80 and 90 °C) induced higher compressive strengths in geopolymers, because the temperature favors the geopolymerization process. Moreover, longer curing times helped to obtain higher compressive strengths for all the cases analyzed. Furthermore, it was found that the most common practice is the use of sodium hydroxide combined with sodium silicate to obtain geopolymers with good mechanical strength, where the optimum SS/NaOH ratio depends on the source of aluminosilicates to be used. Generally speaking, it was observed that higher water contents lead to a decrease in compressive strength. The presence of calcium was found to be favorable in controlled proportions as it increases the compressive strength of geopolymers, on the other hand, impurities such as heavy metals have a negative effect on the compressive strength of geopolymers.

BackgroundDermatological diseases are among the primary causes of the demand for basic health care. Studies on the frequency of dermatoses are important for the proper management of health planning.ObjectivesTo evaluate the nosological and behavioral profiles of dermatological consultations in Brazil.MethodsThe Brazilian Society of Dermatology invited all of its members to complete an online form on patients who sought consultations from March 21-26, 2018. The form contained questions about patient demographics, consultation type according to the patient's funding, the municipality of the consultation, diagnosis, treatments and procedures. Diagnostic and therapeutic decisions were compared between subgroups.ResultsData from 9629 visits were recorded. The most frequent causes for consultation were acne (8.0%), photoaging (7.7%), nonmelanoma skin cancer (5.4%), and actinic keratosis (4.7%). The identified diseases had distinct patterns with regard to gender, skin color, geographic region, type of funding for the consultation, and age group. Concerning the medical conducts, photoprotection was indicated in 44% of consultations, surgical diagnostic procedures were performed in 7.3%, surgical therapeutic procedures were conducted in 19.2%, and cosmetic procedures were performed in 7.1%.Study limitationsNonrandomized survey, with a sample period of one week.ConclusionThis research allowed us to identify the epidemiological profiles of the demands of outpatients for dermatologists in various contexts. The results also highlight the importance of aesthetic demands in privately funded consultations and the significance of diseases such as acne, nonmelanoma skin cancer, leprosy, and psoriasis to public health.