Exact master equation for a noncommutative Brownian particle

We derive the Hu-Paz-Zhang master equation for a Brownian particle linearly coupled to a bath of harmonic oscillators on the plane with spatial noncommutativity. The results obtained are exact to all orders in the noncommutative parameter. As a by-product we derive some miscellaneous results such as the equilibrium Wigner distribution for the reservoir of noncommutative oscillators, the weak coupling limit of the master equation and a set of sufficient conditions for strict purity decrease of the Brownian particle. Finally, we consider a high-temperature Ohmic model and obtain an estimate for the time scale of the transition from noncommutative to ordinary quantum mechanics. This scale is considerably smaller than the decoherence scale.     

Correlations between the Interacting Fragments of Decaying Processes

We study the correlations (and alignment as a particular case) existent between the fragments originated in a decaying process when the daughter particles interact. The interaction between the particles is modeled using the potential of coupled oscillators, which can be treated analytically. This approach can be considered as a first step towards the characterization of realistic interacting decaying systems, an archetypal process in physics. The results presented here also suggest the possibility of manipulating correlations using external fields, a technique that could be useful to provide sources of entangled massive particles.     

Ab initio study of the chemical states of water on Cr2O3(0 0 0 1): From the isolated molecule to saturation coverage

The reactivity of the (0 0 0 1)-Cr–Cr₂O₃ surface towards water was studied by means of periodic DFT + U. Several water coverages were studied, from 1.2H₂O/nm² to 14.1H₂O/nm², corresponding to ¼, 1, 2 and 3 water/Cr at the (0 0 0 1)-Cr₂O₃ surface, respectively. With increasing coverage, water gradually completes the coordination sphere of the surface Cr atoms from 3 (dry surface) to 4 (1.2 and 4.7H₂O/nm²), 5 (9.4H₂O/nm²) and 6 (14.1H₂O/nm²). For all studied coverages, water replaces an O atom from the missing above plane. At coverages 1.2 and 4.7H₂O/nm², the Cr–O_s (surface oxygen) acid–base character and bond directionality govern the water adsorption. The adsorption is molecular at the lowest coverage. At 4.7H₂O/nm², molecular and dissociative states are isoenergetic. The activation energy barrier between the two states being as low as 12 kJ/mol, allowing protons exchanges between the OH groups, as evidenced by ab inito molecular dynamics at room temperature. At coverages of 9.4 and 14.1H₂O/nm², 1D- (respectively, 2D-) water networks are formed. The resulting surface terminations are –Cr(OH)₂ and –Cr(OH)₃– like, respectively. The increased stability of those terminations as compared to the previous ones are due to the stabilization of the adsorbed phase through a H-bond network and to the increase in the Cr coordination number, stabilizing the Cr (t_2g) orbitals in the valence band. An atomistic thermodynamic approach allows us to specify the temperature and water pressure domains of prevalence for each surface termination. It is found that the –Cr(OH)₃-like, –Cr(OH)₂ and anhydrous surfaces may be stabilized depending on (T, P) conditions. Calculated energies of adsorption and OH frequencies are in good agreement with published experimental data and support the full hydroxylation model, where the Cr achieves a 6-fold coordination, at saturation.     

Synthesis and Characterization of Polymeric Materials from Vegetable Oils

Although the petrochemical polymers have revolutionized the technological development, the intensive use of these materials have contributed to the global pollution. In this context, researches involving ecofriendliness materials are growing up, as well as, a current interest in developing materials from inexpensive and renewable resources, such as vegetable oils. In this work, is described the synthesis of polymeric materials by thermal polymerization from linseed oil (Linum usitatissimum L.) and passion fruit oil (Passiflora edulis) and their characterization by gas chromatographic (GC), Fourier transform infrared (FTIR) spectroscopy, solubility in organic solvents, thermogravimetry (TG), differential scanning calorimetry (DSC) and Raman spectroscopy. The TG curve shows that those polymeric materials present two stages of decomposition. DSC plots of the vegetable oils showed some endothermic and exothermic transitions which are not present in the DSC curves corresponding to oil-based polymers. The Raman spectra of the polymers indicate declining of absorbance in the region of CC stretching (∼1600 cm⁻¹). This absorption was used to estimate the degree of polymerization (79% and 67.5% for linseed and passion fruit oils, respectively).     

Some Interesting Observations on the Free Energy Principle

Biehl et al. (2021) present some interesting observations on an early formulation of the free energy principle. We use these observations to scaffold a discussion of the technical arguments that underwrite the free energy principle. This discussion focuses on solenoidal coupling between various (subsets of) states in sparsely coupled systems that possess a Markov blanket—and the distinction between exact and approximate Bayesian inference, implied by the ensuing Bayesian mechanics.     

Michael additions of primary and secondary amines to acrylonitrile catalyzed by lipases

The present Letter details our findings on the lipase-catalyzed Michael reactions between primary or secondary amines and acrylonitrile. Several lipases were evaluated, and good results were obtained leading to the formation of Michael adducts in shorter reaction times than the uncatalyzed reactions.     

MCE‐electrochemical detection for following interactions of ssDNA and dsDNA with methylene blue

The interaction between the organic dye, methylene blue and DNA has been studied by MCE with electrochemical detection. Interaction produces two different signals, one corresponding to free methylene blue and other, for the complex methylene blue–DNA. The hybridization between a ssDNA and a complementary sequence, specific to the severe acute respiratory syndrome virus, has been performed and studied in a thermoplastic olefin polymer of amorphous structure CE‐microchip with an end‐channel gold wire detector. Moreover, studies with a longer dsDNA, an expression vector involved in the transitory or stable expression in mammals cells, pFLAG‐CMV4, has also been performed.     

New organometallic Ru(II) and Fe(II) complexes with tetrathia-[7]-helicene derivative ligands

A series of organometallic complexes possessing new tetrathia-[7]-helicene nitrile derivative ligands [TH-7] as chromophores, of general formula [MCp(P–P)(NC{TH-[7]-Y}Z)][PF₆] (M = Ru, Fe, P–P = DPPE, Y = H, NO₂, Z = H, C≡N; M = Ru, L–L = 2PPh₃, Y = H, Z = H) has been synthesized and fully characterized. ¹H NMR, FT-IR and UV–Vis. spectroscopic data were analyzed with in order to evaluate the existence of electronic delocalization from the metal centre to the coordinated ligand to have some insight on the potentialities of these new compounds as non-linear optical molecular materials. Slow crystallization of compound [RuCp(PPh₃)₂(NC{TH-[7]-H}H)][PF₆] 2Ru revealed an interesting isomerization of the helical ligand with formation of two carbon-carbon bonds between the two terminal thiophenes, leading to the total closure of the helix (2*Ru).     

Regioselectivity Control in the Metal‐Catalyzed Functionalization of γ‐Allenols,Part 2: Theoretical Study

Calculating cyclization : Theoretical work directed towards the elucidation of the mechanisms of the gold‐, palladium‐, and lanthanum‐catalyzed oxycyclizations (5‐exo versus 6‐endo versus 7‐endo) of γ‐allenols has been pursued in close relationship with the experimental study (Part 1, accompanying paper) and has corroborated the bench results to provide a complete study of the reactivity of γ‐allenols under different metal‐catalyzed conditions.