Magnetic inversion symmetry breaking and ferroelectricity in TbMnO3

TbMnO3 is an orthorhombic insulator where incommensurate spin order for temperature T(N)<41 K is accompanied by ferroelectric order for T<28 K. To understand this, we establish the magnetic structure above and below the ferroelectric transition using neutron diffraction. In the paraelectric phase, the spin structure is incommensurate and longitudinally modulated. In the ferroelectric phase, however, there is a transverse incommensurate spiral. We show that the spiral breaks spatial inversion symmetry and can account for magnetoelectricity in TbMnO3.     

Synthesis and transformations of pyrrolo[1,2-a][1,3,5]-triazines

Pyrrolotriazines and related fused azaheterocycles have high potential for the synthesis of bioactive compounds, especially as a purine base isoster in carbon linked nucleosides. Although many structurally related compounds have already been synthesized and used in medicinal chemistry, pyrrolo[1,3,5]triazines have barely been described. The present work describes the synthesis of such heterocycles via condensation of 2-amino-3-ethoxycarbonylpyrrole with ethoxycarbonyliso(thio)cyanate. In a brief reactivity study of the obtained fused pyrroles, O- and S-alkylation, ester hydrolysis as well as regioselective bromination at the 6-position was demonstrated.     

Lessons To Be Learned: The Molecular Basis of Kinase‐Targeted Therapies and Drug Resistance in Non‐Small Cell Lung Cancer

The treatment of non‐small cell lung cancer (NSCLC) is currently experiencing a revolution. Over the last decade, the knowledge gained about the biochemical features of biomarkers and their predictive abilities has led to the development of targeted small‐molecule inhibitors that present an alternative to harsh chemotherapy. The use of these new therapies has improved the quality of life and increased the survival of patients. The occurrence of inevitable drug resistance requires the constant development of precision medicine. The detailed understanding of the target biology and the search for innovative chemical approaches has encouraged investigations in this field. Herein, we review selected aspects of the molecular targets and present an overview of current topics and challenges in the rational development of small molecules to target NSCLC.     

Characterisation of phenolic compounds of the ethyl acetate fraction from Tabernaemontana catharinensis and its potential antidepressant-like effect

This study evaluates the antidepressant-like effect and analysed the qualitative and quantitative 74 phenolic standards of ethyl acetate fraction from Tabernaemontana catharinensis leaves. Acute administration of fraction in mice reduced the immobility time in forced swimming and tail suspension tests confirming its antidepressant-like activity. The anti-immobility effect elicited by this fraction was prevented by the pretreatment of mice with PCPA (100 mg kg^?1), ketanserin (5 mg kg^?1), SCH 23,390 (0.05 mg kg^?1) or yohimbine (1 mg kg^?1). A sub effective dose of the fraction produced a synergistic effect with fluoxetine (5 mg kg^?1). Chromatographic analysis identified 4-hydroxybenzoic and p-coumaric acids in the ethyl acetate fraction from T. catharinensis. Capillary electrophoresis presented 7.34 ± 0.02 mg g^?1 of p-coumaric acid concentration in the fraction. Therefore, it is possible that antidepressant-like effect elicited by ethyl acetate fraction from T. catharinensis be dependent on the p-coumaric acid.     

Stable Boundary Conditions and Discretization for $P_N$ Equations

A solution to the linear Boltzmann equation satisfies an energy bound, which reflects a natural fact: The energy of particles in a finite volume is bounded in time by the energy of particles initially occupying the volume augmented by the energy transported into the volume by particles entering the volume over time. In this paper, we present boundary conditions (BCs) for the spherical harmonic $(P_N)$ approximation, which ensure that this fundamental energy bound is satisfied by the $P_N$ approximation. Our BCs are compatible with the characteristic waves of $P_N$ equations and determine the incoming waves uniquely. Both, energy bound and compatibility, are shown on abstract formulations of $P_N$ equations and BCs to isolate the necessary structures and properties. The BCs are derived from a Marshak type formulation of BC and base on a non-classical even/odd-classification of spherical harmonic functions and a stabilization step, which is similar to the truncation of the series expansion in the $P_N$ method. We show that summation by parts (SBP) finite difference on staggered grids in space and the method of simultaneous approximation terms (SAT) allows to maintain the energy bound also on the semi-discrete level.     

A model for π-selfadjoint operators in π1 and a special linear pencil

The eigenvalue of nonpositive type of a -selfadjoint operator A in a Pontrjagin space of index one is characterized in a model of A. Similar questions are studied for an eigen-value problem G-T in a Hilbert space with a selfadjoint operator T and a special operator G.     

Mechanism of Ru(II)-catalyzed olefin insertion and C-H activation from quantum chemical studies

The mechanism of catalytic hydroarylation of olefins by the homogeneous Ru(Tp)(CO)(Ph)(NCCH3) catalyst recently reported by Gunnoe et al. is characterized using quantum mechanics (density functional theory). The catalytic cycle features two key steps, 1,2-olefin insertion and C-H activation via an unusual mechanism, oxidative hydrogen migration. We find that these two key steps are competitive and that improving the rate of one step is detrimental to the rate of the other. The Ru catalyst has better balance and consequently higher activity than the previously explored Ir-based system.     

Mono- und dicarbenkomplexe durch reaktion von pentacarbonyleisen mit einigen dialkylamiden des zwei- und vierwertigen zinns

The dialkylamides of tin react with ironpentacarbonyl to form carbene complexes. With Me₂Sn(NMe₂)₂ and Sn(NMe₂)₄ yellow dicarbene complexes are formed by addition of two Sn---N bonds to adjacent carbonyl groups. The two carbenoid systems on the central atom are parts of a chelate ligand connected by an ---O---Sn---O--- bridge. Using [Sn(NMe₂)₂]₂, a red monomeric compound (CO)₃Fe(CONMe₂)₂Sn containing the same cyclic structural unit can be isolated. The free activation enthalpy of rotation about the C(carbene)---N bond in the tin (IV) dicarbene complexes was found to be 16.5 kcal mol^-1.