Modeling the shear-dependent viscosity of nonionically stabilized waterborne dispersions

[EN] The performance of a rheological model that accounts for the effect of the volume fraction, the particle size distribution, and shear rate on the viscosity of water-borne dispersions stabilized with conventional nonionic surfactants and polymeric stabilizers is assessed. The model that contains three parameters fitted well the experimental data. The parameters were independent of the volume fraction, the particle size distribution, and the shear rate. Furthermore, two of them were not affected by the surfactant type and concentration, and temperature. The other parameter increased with the surfactant molecular weight and surface covering, but decreased with increasing temperature.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This study was supported by Ministerio de Ciencia e Innovacion (PID2019-107889GA-I00)

Historia de las teorías embriológicas (S. XVII - S.XX): reconstrucción racional según las epistemologías de Lakatos y Kuhn

Ningun

Producción de látex híbridos acrílicos/alquídicos

In this work, the production of high solids content hybrid acrylic/alkyd latexes by miniemulsion polymerization is discussed. First, the miniemulsification procedure to achieve colloidally stable hybrid nanodroplets is presented. Next, the efficient nucleation of most nanodroplets during the polymerization, avoiding other nucleation mechanisms is presented. Finally, the key aspects to control the polymer architecture as well as the particle morphology are analyzed.Fil: Goikoetxea, Monika. Universidad del País Vasco; EspañaFil: Minari, Roque Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Beristain, Itxaso. Universidad del País Vasco; EspañaFil: Paulis, María. Universidad del País Vasco; EspañaFil: Asua, José M.. Universidad del País Vasco; EspañaFil: Barandiaran, María J.. Universidad del País Vasco; Españ

The use of potymerisable surfactants in emulsión copolymerization for coatings applications

In this paper results obtained in high solids contení emulsión copolymerizations using polymerizable surfactcmts (surfmers) have been reviewed On the basis of the interpretation of the behavior of the surfmers (the conversión vs. time and their performance in stability tests and film properties), an optimal surfmer behavior has been defined, which means that all the added surfmer groups end up on the particle surface rather than being buried, which leads to inferior látex stability. One of the strategies that have been proposed to achieve this has been applied to prepare a well-defined styrene-butyl acrylate látex of which film can be easily be casi. Its properties in terms of mechanical stability, film water absorption, and film surfactant exhudation have been assessed and compared with these of a similar látex with sodiicm dodecyl sulfate. Other comonomer Systems have been studied as well with the maleic surfmer. In these Systems the surfmer behavior was less “optimum ”. For these lotices both mechanical stability and water absorption was assesse

Recent developments in miniemulsion polymerization

Some developments in miniemulsion polymerization aiming at taking advantage of its unique mechanisms minimizing the drawbacks of this technique are discussed. The discussion ineludes preparation of highly concentrated latexes, miniemulsion polymerization in continuous stirred tank reactors (CSTRs), and elimination of the low molecular weight hydrophobe

Biomechanical evaluation of oversized drilling technique on primary implant stability measured by insertion torque and resonance frequency analysis

Background: This study evaluated the influence of implant site preparation depth on primary stability measured by insertion torque and resonance frequency analysis (RFA). Material and Methods: Thirty-two implant sites were prepared in eight veal rib blocks. Sixteen sites were prepared using the conventional drilling sequence recommended by the manufacturer to a working depth of 10mm. The remaining 16 sites were prepared using an oversize drilling technique (overpreparation) to a working depth of 12mm. Bone density was determined using cone beam computerized tomography (CBCT). The implants were placed and primary stability was measured by two methods: insertion torque (Ncm), and RFA (implant stability quotient [ISQ]). Results: The highest torque values were achieved by the conventional drilling technique (10mm). The ANOVA test confirmed that there was a significant correlation between torque and drilling depth (p<0.05). However, no statistically significant differences were obtained between ISQ values at 10 or 12 mm drilling depths (p>0.05) at either measurement direction (cortical and medullar). No statistical relation between torque and ISQ values was identified, or between bone density and primary stability (p>0.05). Conclusions: Vertical overpreparation of the implant bed will obtain lower insertion torque values, but does not produce statistically significant differences in ISQ values

Changing antimalarial drug resistance patterns identified by surveillance at three sites in Uganda.

: We assessed Plasmodium falciparum drug resistance markers in parasites collected in 2012, 2013, and 2015 at 3 sites in Uganda. The prevalence and frequency of parasites with mutations in putative transporters previously associated with resistance to aminoquinolines, but increased sensitivity to lumefantrine (pfcrt 76T; pfmdr1 86Y and 1246Y), decreased markedly at all sites. Antifolate resistance mutations were common, with apparent emergence of mutations (pfdhfr 164L; pfdhps 581G) associated with high-level resistance. K13 mutations linked to artemisinin resistance were uncommon and did not increase over time. Changing malaria treatment practices have been accompanied by profound changes in markers of resistance.<br/

Drug susceptibility of Plasmodium falciparum in eastern Uganda: a longitudinal phenotypic and genotypic study

Background: Treatment and control of malaria depends on artemisinin-based combination therapies (ACTs) and is challenged by drug resistance, but thus far resistance to artemisinins and partner drugs has primarily occurred in southeast Asia. The aim of this study was to characterise antimalarial drug susceptibility of Plasmodium falciparum isolates from Tororo and Busia districts in Uganda. Methods: In this prospective longitudinal study, P falciparum isolates were collected from patients aged 6 months or older presenting at the Tororo District Hospital (Tororo district, a site with relatively low malaria incidence) or Masafu General Hospital (Busia district, a high-incidence site) in eastern Uganda with clinical symptoms of malaria, a positive Giemsa-stained blood film for P falciparum, and no signs of severe disease. Ex-vivo susceptibilities to ten antimalarial drugs were measured using a 72-h microplate growth inhibition assay with SYBR Green detection. Relevant P falciparum genetic polymorphisms were characterised by molecular methods. We compared results with those from earlier studies in this region and searched for associations between drug susceptibility and parasite genotypes. Findings: From June 10, 2016, to July 29, 2019, 361 P falciparum isolates were collected in the Busia district and 79 in the Tororo district from 440 participants. Of 440 total isolates, 392 (89%) successfully grew in culture and showed excellent drug susceptibility for chloroquine (median half-maximal inhibitory concentration [IC50] 20·0 nM [IQR 12·0-26·0]), monodesethylamodiaquine (7·1 nM [4·3-8·9]), pyronaridine (1·1 nM [0·7-2·3]), piperaquine (5·6 nM [3·3-8·6]), ferroquine (1·8 nM [1·5-3·3]), AQ-13 (24·0 nM [17·0-32·0]), lumefantrine (5·1 nM [3·2-7·7]), mefloquine (9·5 nM [6·6-13·0]), dihydroartemisinin (1·5 nM [1·0-2·0]), and atovaquone (0·3 nM [0·2-0·4]). Compared with results from our study in 2010-13, significant improvements in susceptibility were seen for chloroquine (median IC50 288·0 nM [IQR 122·0-607·0]; p\u3c0·0001), monodesethylamodiaquine (76·0 nM [44·0-137]; p\u3c0·0001), and piperaquine (21·0 nM [7·6-43·0]; p\u3c0·0001), a small but significant decrease in susceptibility was seen for lumefantrine (3·0 nM [1·1-7·6]; p\u3c0·0001), and no change in susceptibility was seen with dihydroartemisinin (1·3 nM [0·8-2·5]; p=0·64). Chloroquine resistance (IC50\u3e100 nM) was more common in isolates from the Tororo district (11 [15%] of 71), compared with those from the Busia district (12 [4%] of 320; p=0·0017). We showed significant increases between 2010-12 and 2016-19 in the prevalences of wild-type P falciparum multidrug resistance protein 1 (PfMDR1) Asn86Tyr from 60% (391 of 653) to 99% (418 of 422; p\u3c0·0001), PfMDR1 Asp1246Tyr from 60% (390 of 650) to 90% (371 of 419; p\u3c0·0001), and P falciparum chloroquine resistance transporter (PfCRT) Lys76Thr from 7% (44 of 675) to 87% (364 of 417; p\u3c0·0001). Interpretation: Our results show marked changes in P falciparum drug susceptibility phenotypes and genotypes in Uganda during the past decade. These results suggest that additional changes will be seen over time and continued surveillance of susceptibility to key ACT components is warranted. Funding: National Institutes of Health and Medicines for Malaria Venture