Synthesis of "two-story" calix[6]aza-cryptands

The first four members of a new family of C(3v)-symmetrical "two-story" calix[6]aza-cryptands have been synthesized. These large funnel shaped aza-ligands are formed through introduction of three aromatic arms as spacers onto the small rim of a calix[6]arene and subsequently capped with the tripodal aza caps tacn [1,3,5-triazacyclononane] or tren [tris(aminoethyl)amine]. A key feature for an efficient final 1:1 macrocyclization appears to be an adequate geometrical fit between the extended calixarene scaffold and the aza caps.     

Biodegradable poly(ethylene carbonate) nanoparticles as a promising drug delivery system with "stealth" potential

The goal of this study was to investigate the suitability of poly(ethylene carbonate) (PEC) nanoparticles as a novel drug delivery system, fulfilling the requirements for a long circulation time. Particles were obtained with a narrow size distribution and nearly neutral zeta potential. Adsorption studies with human plasma proteins revealed that PEC nanoparticles bind much less proteins in comparison to polystyrene (PS) nanoparticles. Cell experiments with fluorescently labeled PEC showed no uptake of the nanoparticles by macrophages. These novel PEC nanospheres with their unique surface properties are a promising candidate for long circulating drug delivery systems in vivo.     

Geospatial model of COVID-19 spreading and vaccination with event Gillespie algorithm

We have developed a mathematical model and stochastic numerical simulation for the transmission of COVID-19 and other similar infectious diseases that accounts for the geographic distribution of population density, detailed down to the level of location of individuals, and age-structured contact rates. Our analytical framework includes a surrogate model optimization process to rapidly fit the parameters of the model to the observed epidemic curves for cases, hospitalizations, and deaths. This toolkit (the model, the simulation code, and the optimizer) is a useful tool for policy makers and epidemic response teams, who can use it to forecast epidemic development scenarios in local settings (at the scale of cities to large countries) and design optimal response strategies. The simulation code also enables spatial visualization, where detailed views of epidemic scenarios are displayed directly on maps of population density. The model and simulation also include the vaccination process, which can be tailored to different levels of efficiency and efficacy of different vaccines. We used the developed framework to generate predictions for the spread of COVID-19 in the canton of Geneva, Switzerland, and validated them by comparing the calculated number of cases and recoveries with data from local seroprevalence studies.

     

Automated densimetric system: Measurements and uncertainties for compressed fluids

In this work, we present the automatization of a densimetric system for pVT measurements of compressed fluids, operating over the temperature range from 283.15 K to 398.15 K and pressures up to 70 MPa. The heart of the automatic assembly is a commercial Anton Paar DMA HPM vibrating-tube densimeter. The densimeter was calibrated using the method developed by Lagourette et al. and modified recently by Comuñas et al. The fluids used in this calibration were a vacuum, water, and n-decane. Data reliability has been verified by comparing our experimental results for toluene with literature data. The uncertainty of the experimental density was evaluated following the rigorous procedure of the EA-4/02 guide. Moreover, new density measurements of pentaerythritol tetrapentanoate ester are presented. For this fluid with significant viscosity values, a correction factor was applied to take into account the damping effects in the densimeter cell.     

A characterization theorem for geometric logic

We establish a criterion for deciding whether a class of structures is the class of models of a geometric theory inside Grothendieck toposes; then we specialize this result to obtain a characterization of the infinitary first-order theories which are geometric in terms of their models in Grothendieck toposes, solving a problem posed by Ieke Moerdijk in 1989.     

Steady flow in the Willis circle using a Quemada model

The paper presents new results on the dynamics of blood flow in the Willis circle, by taking into account the non-Newtonian nature of the blood through a Quemada model. In previous papers we performed a steady analysis of the blood flow in the Willis polygon, by considering the blood as a Newtonian fluid. In hemodynamics this is the first step, while taking into account the non-Newtonian behaviour of the fluid is called a second order approach. This is in fact the aim of our paper, to compare the results (blood flow rates and pressures) obtained in a non-Newtonian approach with those furnished by a Newtonian modeling of the blood. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Proof of a conjecture on a congruence modulo 243 for overpartitions

Periodica Mathematica Hungarica - Let $$\bar{p}(n)$$ denote the number of overpartitions of n. Recently, numerous congruences modulo powers of 2, 3 and 5 were established regarding $$\bar{p}(n)$$ ....