Stereoisomers composition of 4-[(1′-methylpropyl)-oxycarbonyl]-2-oxetanone and related compounds,as precursors of fuctional polyesters,determined by chiral gas chromatography

Summary The configurational analysis of racemic and optically active stereoisomers of 4-[(1-methylpropyl)oxycarbonyl]-2-oxetanone has been carried out by using chiral gas chromatography. This technique has been successful in the stereoisomers composition determination of these -substituted -lactones prepared by two different routes and used as monomers in the preparation of malic acid stereocopolymers. Result are in good agreement with those obtained from high resolution ¹H NMR, in the presence of an Europium salt, as chiral shift reagent. This method has been extended to 3-methyl-4-[(1,2,2-trimethyl propyl)oxycarbonyl]-2-oxetanone. The exact knowledge of precursors configurational structure is very important in regard to the obtention of the corresponding polystereoisomers with a strictly controlled enantiomeric or diastereoisomeric composition and consequently with predictable properties.     

Exploiting ELIOT for Scaffold-Repurposing Opportunities: TRIM33 a Possible Novel E3 Ligase to Expand the Toolbox for PROTAC Design

The field of targeted protein degradation, through the control of the ubiquitin–proteasome system (UPS), is progressing considerably; to exploit this new therapeutic modality, the proteolysis targeting chimera (PROTAC) technology was born. The opportunity to use PROTACs engaging of new E3 ligases that can hijack and control the UPS system could greatly extend the applicability of degrading molecules. To this end, here we show a potential application of the ELIOT (E3 LIgase pocketOme navigaTor) platform, previously published by this group, for a scaffold-repurposing strategy to identify new ligands for a novel E3 ligase, such as TRIM33. Starting from ELIOT, a case study of the cross-relationship using GRID Molecular Interaction Field (MIF) similarities between TRIM24 and TRIM33 binding sites was selected. Based on the assumption that similar pockets could bind similar ligands and considering that TRIM24 has 12 known co-crystalised ligands, we applied a scaffold-repurposing strategy for the identification of TRIM33 ligands exploiting the scaffold of TRIM24 ligands. We performed a deeper computational analysis to identify pocket similarities and differences, followed by docking and water analysis; selected ligands were synthesised and subsequently tested against TRIM33 via HTRF binding assay, and we obtained the first-ever X-ray crystallographic complexes of TRIM33α with three of the selected compounds.     

Electrochemical and thermodynamic properties of ytterbium trichloride in molten caesium chloride

This work presents the electrochemical study of YbCl₃ in molten CsCl in the temperature range 973-1073 K. Transient electrochemical techniques have been used in order to investigate the reduction mechanism, transport parameters and thermodynamics properties of the reaction YbCl₂+1/2Cl₂=YbCl₃. The results obtained show that the reduction reaction is reversible being controlled by the rate of the mass transfer. The diffusion coefficient of [YbCl₆]^3- complex ions was determined. The apparent standard electrode potential of the soluble-soluble redox system Yb³⁺/Yb²⁺ was obtained by cyclic voltammetry.     

Ferroelectric order in individual nanometre-scale crystals

Ferroelectricity in finite-dimensional systems continues to arouse interest, motivated by predictions of vortex polarization states and the utility of ferroelectric nanomaterials in memory devices, actuators and other applications. Critical to these areas of research are the nanoscale polarization structure and scaling limit of ferroelectric order, which are determined here in individual nanocrystals comprising a single ferroelectric domain. Maps of ferroelectric structural distortions obtained from aberration-corrected transmission electron microscopy, combined with holographic polarization imaging, indicate the persistence of a linearly ordered and monodomain polarization state at nanometre dimensions. Room-temperature polarization switching is demonstrated down to ~5?nm dimensions. Ferroelectric coherence is facilitated in part by control of particle morphology, which along with electrostatic boundary conditions is found to determine the spatial extent of cooperative ferroelectric distortions. This work points the way to multi-Tbit/in(2) memories and provides a glimpse of the structural and electrical manifestations of ferroelectricity down to its ultimate limits.     

Unsteady fluid mechanics and heat transfer study in a double-tube air–combustor heat exchanger with porous medium

Fluid mechanics and heat transfer are studied in a double-tube heat exchanger that uses the combustion gases from natural gas in a porous medium located in a cylindrical tube to warm up air that flows through a cylindrical annular space. The mathematical model is constructed based on the equations of continuity, linear momentum, energy and chemical species. Unsteady fluid mechanics and heat transfer by forced gas convection in the porous media, with combustion in the inner tube, coupled to the forced convection of air in the annular cylindrical space are predicted by use of finite volumes method. Numerical simulations are made for four values of the annular air flow Reynolds number in the range 100 ? Re ? 2000, keeping constant the excess air ψ = 4.88, the porosity ε = 0.4, and the air–fuel mixture inlet speed Uo = 0.43 m/s. The results obtained allow the characterization of the velocity and temperature distributions in the inner tube and in the annular space, and at the same time to describe the displacement of the moving combustion zone and the annular porous media heat exchanger thermal efficiency. It is concluded that the temperature increase is directly related to the outer Reynolds number.     

Multi-objective design optimization of a new space radiator

In this work different multi-objective techniques are used to the conceptual design of a new kind of space radiator. Called VESPAR (Variable Emittance Space Radiator), the radiator has an effective variable emittance which makes it able to reduce or avoid the demand for heater power to warm up equipment during cold case operations in orbit. The multi-objective approach was aimed on obtaining a radiator that minimize its mass while at the same time minimize the need for heater power during cold case. Four multi-objective algorithms were used: Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II), Multi-Objective Genetic Algorithm (MOGA), Multi-Objective Simulating Annealing (MOSA) and Multi-Objective Generalized Extremal Optimization (M-GEO). The first three algorithms were used under the modeFrontier^® optimization software package, while M-GEO is a recently proposed multi-objective implementation of the Generalized Extremal Optimization (GEO) algorithm. The Pareto frontier showing the trade-off solutions between radiator mass and heater power consumption is obtained by the four algorithms and the results compared. An assessment of the performance of M-GEO on this problem, compared to the other well-known multi-objective algorithms is also made.     

Retardation of the merocyanine-spiropyran conversion in macromolecules

Summary The flash photolysis of photochromic poly(spiropyranmethacrylate) in solutions was studied. The rates of the thermal decoloration reaction in the polymer solutions are lower than in solutions of the monomer, that was attributed to the steric hindrance of the reaction in macromolecules.     

Kinetic modeling of the laser-induced breakdown spectroscopy plume from metallic lead

We report initial results of a study aimed toward developing a computational fluid dynamics (CFD) model to simulate the laser-induced breakdown spectroscopy (LIBS) plume for the purpose of understanding the physical and chemical factors that control the LIBS signature. The kinetic model developed for modeling studies of the LIBS plume from metallic lead includes a set of air reactions and ion chemistry as well as the oxidization, excitation, and ionization of lead atoms. At total of 38 chemical species and 220 reactions are included in the model. Experimental measurements of the spatial and temporal dependence of a number of lead emission lines have been made of the LIBS plume from metallic lead. The mechanism of generation of excited Pb states in the LIBS plume is analyzed through kinetic modeling and sensitivity analysis. Initial CFD model results for the LIBS plume are presented.