Transition from viscous to inertial regime in dense suspensions

Non-Brownian suspensions present a transition from Newtonian behavior in the zero-shear limit to a shear thickening behaviour at a large shear rate, none of which is clearly understood so far. Here, we carry out numerical simulations of such an athermal dense suspension under shear, at an imposed confining pressure. This set-up is conceptually identical to the recent experiments of Boyer and co-workers [Phys. Rev. Lett. 107,188301 (2011)]. Varying the interstitial fluid viscosities, we recover the Newtonian and Bagnoldian regimes and show that they correspond to a dissipation dominated by viscous and contact forces respectively. We show that the two rheological regimes can be unified as a function of a single dimensionless number, by adding the contributions to the dissipation at a given volume fraction.Comment: 4 pages, 3 figure

Synthesis of fucose derivatives with thiol motifs towards suicide inhibition of helicobacter pylori

The syntheses of six thiol-exhibiting monosaccharides towards suicide inhibition of Helicobacter pylori are reported. Blood group Antigen Binding Adhesin (BabA), a bacterial membrane-bound lectin, binds to human ABO and Lewis b blood group structures displayed on the surface of host epithelial cells. Crystal structures of the carbohydrate-recognition domain revealed a conserved disulfide bonded loop that anchors a critical fucose residue in these blood group structures. Disruption of this loop by N-acetylcysteine results in reduced BabA-mediated adherence to human gastric tissue sections and attenuated virulence in Lewis b-expressing transgenic mice. With a view of creating specific inhibitors of the lectin, we designed and successfully synthesised six fucose-derived compounds with thiol motifs to engage in a thiol-disulfide exchange with this disulfide bond of BabA and form a glycan-lectin disulfide linkage. Branching and extending the fucose backbone with 2- and 3-carbon thiol motifs delivered a range of candidates to be tested for biological activity against BabA

Adaptabilidade de linhagens e cultivares de feijao (Phaseolus vulgaris L.) em Rondonia e resistencia a "mela" (Thanatephorus cucumeris (Frank.) Donk).

bitstream/item/60390/1/PA-1588-0001.pd

Labeling of Activity Recognition Datasets: Detection of Misbehaving Users

Automatic recognition of user’s activities by means of wearable devices is a key element of many e-health applications, ranging from rehabilitation to monitoring of elderly citizens. Activity recognition methods generally rely on the availability of annotated training sets, where the traces collected using sensors are labelled with the real activity carried out by the user. We propose a method useful to automatically identify misbehaving users, i.e. the users that introduce inaccuracies during the labeling phase. The method is semi-supervised and detects misbehaving users as anomalies with respect to accurate ones. Experimental results show that misbehaving users can be detected with more than 99% accuracy

Selectively charged and zwitterionic analogues of the smallest immunogenic structure of Streptococcus pneumoniae type 14

Zwitterionic polysaccharides (ZPs) have been shown in recent years to display peculiar immunological properties, thus attracting the interest of the carbohydrate research community. To fully elucidate the mechanisms underlying these properties and exploit the potential of this kind of structures, in depth studies are still required. In this context, the preparation of two cationic, an anionic, as well as two zwitterionic tetrasaccharide analogues of the smallest immunogenic structure of Streptococcus pneumoniae type 14 (SP14) capsular polysaccharide are presented. By exploiting a block strategy, the negative charge has been installed on the non-reducing end of the lactose unit of the tetrasaccharide and the positive charge either on the non-reducing end of the lactosamine moiety or on an external linker. These structures have then been tested by competitive ELISA, showing that the structural variations we made do not modify the affinity of the neutral compound to binding to a specific antibody. However, lower efficacies than the natural SP14 compound were observed. The results obtained, although promising, point to the need to further elongate the polysaccharide structure, which is likely too short to cover the entire epitopes

Remarkable effect of [Li(G4)]TFSI solvate ionic liquid (SIL) on the regio- And stereoselective ring opening of α-gluco carbasugar 1,2-epoxides

Carba analogues of biologically relevant natural carbohydrates are promising structures for the development of future drugs endowed with enhanced hydrolytic stability. An open synthetic challenge in this field is the optimization of new methodologies for the stereo- and regioselective opening of α-gluco carbasugar 1,2-epoxides that allow for the preparation of pseudo mono- and disaccharides of great interest. Therefore, we investigated the effect of Lewis acids and solvate ionic liquids (SILs) on the epoxide ring opening of a model substrate. Of particular interest was the complete stereo- and regioselectivity, albeit limited to simple nucleophiles, toward the desired C(1) isomer that was observed using LiClO4. The results obtained with SILs were also remarkable. In particular, Li[NTf2]/tetraglyme ([Li(G4)]TFSI) was able to function as a Lewis acid and to direct the attack of the nucleophile preferentially at the pseudo anomeric position, even with a more complex and synthetically interesting nucleophile. The regioselectivity observed for LiClO4 and [Li(G4)]TFSI was tentatively ascribed to the formation of a bidentate chelating system, which changed the conformational equilibrium and ultimately permitted a trans-diaxial attack on C(1). To the best of our knowledge, we report here the first case in which SILs were successfully employed in a ring-opening process of epoxides

Polimorfismo N363S do gene do receptor de glucocorticoide: efeito sobre a adiposidade visceral medida pela tomografia computadorizada

OBJECTIVE: To verify whether N363S polymorphism of the glucocorticoid receptor-gene can be associated to visceral fat by CT scan in obese individuals, and the impact of this variant on metabolic profile. METHODS: The N363S variant was screened in 295 Brazilians, 195 were obese and 100 presented normal weight. Based on genotype, obese N363S SNP carriers were paired with obese wild-type subjects. This group was submitted to a CT scan and metabolic profile assessment. RESULTS: Ten subjects were found to be heterozygous for the variant (A/G genotype frequency 3.4%), 8 (4.1%) obese and 2 (2.0%) non-obese. No differences were reported for visceral adiposity area (145.8 ± 49.9 vs.147.7 ± 48.8 cm²; p = 0.92) based on CT scan results but N363S SNP carriers showed a proneness to unfavorable metabolic changes. CONCLUSION: The N363S polymorphism prevalence is low in the Brazilian population, although its presence may contribute to the worsening of individuals' metabolic profiles.OBJETIVO: Verificar se a presença do polimorfismo N363S do gene do receptor de glucocorticoide estaria associada, em indivíduos obesos, à presença de adiposidade visceral pela tomografia computadorizada, e sobre o impacto desta variante genética no perfil metabólico. MÉTODOS: A variante N363S do receptor do glicocorticoide foi verificada em um grupo de 295 indivíduos brasileiros, sendo 295 obesos e 100 com peso normal. Com base na genotipagem, os indivíduos obesos carreadores do polimorfismo N363S foram pareados com obesos normais. O grupo com polimorfismo foi submetido a exames de tomografia computadorizada abdominal e laboratoriais para a caracterização de seu perfil metabólico. RESULTADOS: Dez indivíduos eram heterozigotos para a variante AG (3,4%), sendo oito obesos (4,1%) e dois não-obesos (2%). Não foram encontradas diferenças na quantidade de adiposidade visceral (145,8 ± 49,9 versus 147,7 ± 48,8 cm²; p = 0,92) baseados no TC de abdômen. No entanto, os indivíduos carreadores do N363S SNP (single nucleotide polymorphism) apresentaram tendência a perfil metabólico desfavorável. CONCLUSÃO: O polimorfismo N363S do gene do receptor de glucocorticoide teve prevalência baixa na população estudada. A sua presença pode contribuir para a deterioração do perfil metabólico desses indivíduos

pH-responsive nanostructures based on surface active fatty acid-protic ionic liquids for imiquimod delivery in skin cancer topical therapy

or topical treatment of skin cancer, the design of pH-responsive nanocarriers able to selectively release the drug in the tumor acidic microenvironment represents a reliable option for targeted delivery. In this context, a series of newly synthesized surface-active fatty acid-protic ionic liquids (FA-PILs), based on tetramethylguanidinium cation and different natural hydrophobic fatty acid carboxylates, have been investigated with the aim of developing a pH-sensitive nanostructured drug delivery system for cutaneous administration in the skin cancer therapy. The capability of FA-PILs to arrange in micelles when combined with each other and with the non-ionic surfactant d-α-Tocopherol polyethylene glycol succinate (vitamin E TPGS) as well as their ability to solubilize imiquimod, an immuno-stimulant drug used for the treatment of skin cancerous lesions, have been demonstrated. The FA-PILs-TPGS mixed micelles showed pH-sensitivity, suggesting that the acidic environment of cancer cells can trigger nanostructures’ swelling and collapse with consequent rapid release of imiquimod and drug cytotoxic potential enhancement. The in vitro permeation/penetration study showed that the micellar formulation produced effective imiquimod concentrations into the skin exposed to acid environment, representing a potential efficacious and selective drug delivery system able to trigger the drug release in the tumor tissues, at lower and less irritating drug concentrations. © 2020 by the author

Chiral biobased ionic liquids with cations or anions including bile acid building blocks as chiral selectors in voltammetry

Chiral ionic liquids (CILs), or ionic liquids (ILs) with chiral additives, are very attractive chiral media for enantioselective electroanalysis, on account of their high chiral structural order at the electrochemical interphase. A family of molecular salts with CIL properties is now introduced, based on the chiral steroid building block of deoxycholic acid implemented either in the anion or cation. Testing them as chiral additives in a commercial achiral IL, they enable voltammetric discrimination of the enantiomers of a model chiral probe on disposable screen-printed electrodes in terms of peak potential differences, which is the most desirable transduction mode of the enantiorecognition event. The probe enantiomer sequence is the same for all selectors, consistent with their sharing the same chiral building block configuration. This proof-of-concept widens the application fields of bile acid derivatives as chiral selectors, while also enriching the still very few CIL families so far explored for applications in chiral electroanalysis

Active and driven hydrodynamic crystals

Motivated by the experimental ability to produce monodisperse particles in microfluidic devices, we study theoretically the hydrodynamic stability of driven and active crystals. We first recall the theoretical tools allowing to quantify the dynamics of elongated particles in a confined fluid. In this regime hydrodynamic interactions between particles arise from a superposition of potential dipolar singularities. We exploit this feature to derive the equations of motion for the particle positions and orientations. After showing that all five planar Bravais lattices are stationary solutions of the equations of motion, we consider separately the case where the particles are passively driven by an external force, and the situation where they are self-propelling. We first demonstrate that phonon modes propagate in driven crystals, which are always marginally stable. The spatial structure of the eigenmodes depend solely on the symmetries of the lattices, and on the orientation of the driving force. For active crystals, the stability of the particle positions and orientations depends not only on the symmetry of the crystals but also on the perturbation wavelengths and on the crystal density. Unlike unconfined fluids, the stability of active crystals is independent of the nature of the propulsion mechanism at the single particle level. The square and rectangular lattices are found to be linearly unstable at short wavelengths provided the volume fraction of the crystals is high enough. Differently, hexagonal, oblique, and face-centered crystals are always unstable. Our work provides a theoretical basis for future experimental work on flowing microfluidic crystals.Comment: 10 pages, 10 figure