Synthesis of lupeol derivatives and their antileishmanial and antitrypanosomal activities

The natural product lupeol 1 was isolated from aerial parts of Vernonia scorpioides with satisfactory yield, which made it viable to be used as starting material in semisynthetic approach. Ten lupeol derivatives 2–11 were prepared by classical procedures. Including, five new esters derivatives 7–11, which were obtained by structural modifications in the isopropylidene fragment. All semisynthetic compounds and lupeol 1–11 were confirmed by ¹H NMR, ¹³C NMR and HRMS. Their antiprotozoal activity was evaluated in vitro against L. amazonensis and T. cruzi. Derivative 6 showed the best antitrypanosomal activity (IC₅₀ = 12.48 μg/mL) and the lowest cytotoxic derivative (CC₅₀ = 161.50 μg/mL). The mechanism of action of the most active derivatives (4, 6 and 11) is not dependent from the enzyme trypanothione reductase.     

Quantum mechanical modeling of Zn-based spinel oxides: Assessing the structural,vibrational, and electronic properties

The structural, electronic, and vibrational properties of two leading representatives of the Zn-based spinel oxides class, normal ZnX₂O₄ (X = Al, Ga, In) and inverse Zn₂MO₄ (M = Si, Ge, Sn) crystals, were investigated. In particular, density functional theory (DFT) was combined with different exchange-correlation functionals: B3LYP, HSE06, PBE0, and PBESol. Our calculations showed good agreement with the available experimental data, showing a mean percentage error close to 3% for structural parameters. For the electronic structure, the obtained HSE06 band-gap values overcome previous theoretical results, exhibiting a mean percentage error smaller than 10.0%. In particular, the vibrational properties identify the significant differences between normal and inverse spinel configurations, offering compelling evidence of a structure-property relationship for the investigated materials. Therefore, the combined results confirm that the range-separated HSE06 hybrid functional performs the best in spinel oxides. Despite some points that cannot be directly compared to experimental results, we expect that future experimental work can confirm our predictions, thus opening a new avenue for understanding the structural, electronic, and vibrational properties in spinel oxides.     

Minimal Contact Circuits for Symmetric Threshold Functions

Mathematical Notes - For the monotone symmetric threshold Boolean functions $$ f^n_2(\widetilde x\mspace{2mu})=\bigvee_{1\le i     

Discrete Vortices in Systems of Coupled Nonlinear Oscillators: Numerical Results for an Electric Model

JETP Letters - Vortex coherent structures on arrays of nonlinear oscillators joined by weak links into topologically nontrivial two-dimensional discrete manifolds have been theoretically studied. A...     

Weak Coupling between Light and Matter in Photonic Crystals Based on Porous Silicon Responsible for the Enhancement of Fluorescence of Quantum Dots under Two-Photon Excitation

JETP Letters - The development of optical and, in particular, photoluminescent sensors is currently becoming more and more significant because of their universality, selectivity, and high...     

Static Approach to Renormalization Group Analysis of Stochastic Models with Spatially Quenched Noise

Journal of Statistical Physics - A new “static” renormalization group approach to stochastic models of fluctuating surfaces with spatially quenched noise is proposed in which only...     

“It’s better to forget physics”: The Idea of the Tactical Nuclear Weapon in the Early Cold War

Physics in Perspective - The American physicist John Wheeler once told his colleague Richard Feynman that, in case of war, “it’s better to forget physics and tell the admirals and...     

Development of a Technique for the Express Assessment of Temperature Fields on the Outlet Window Membrane of the LUE-200 Accelerator

Physics of Particles and Nuclei Letters - A technique has been developed for express estimation of temperature fields using a graded curve, which can be used to justify the reliability and safety...