Optimal descriptor as a translator of eclectic information into the prediction of thermal conductivity of micro-electro-mechanical systems

Micro-electro-mechanical systems (MEMS) are involved in various fields of nanotechnology. MEMS are characterized by complex and unclear molecular architecture. However, in most cases information about chemical composition and conditions of synthesis is available. One-variable models for thermal conductivity of MEMS are suggested. These models are based on the representation of MEMS by their chemical composition and technological attributes. We have examined three random splits of available data into the training set and validation set. The average statistical characteristics of these models are quite good. Development of suggested here models is carried out without information on molecular architecture of MEMS.     

The definition of the molecular structure for potential anti-malaria agents by the Monte Carlo method

A series of 53 endochin analogs (4(1-H)-quinolone derivatives) with anti-malarial activity against the clinically relevant multidrug resistant malarial strain TM-90-C2B has been studied. The CORAL (http://www.insilico.eu/coral) software has been used as a tool to build up the quantitative structure–activity relationships (QSAR) for the anti-malaria activity. The QSAR models were calculated with the representation of the molecular structure by simplified molecular input-line entry system and by the molecular graph of atomic orbitals. The method for splitting data into the sub-training set, the calibration set, the test set, and the validation set is suggested. Three various splits were examined. Statistical quality of models for the validation sets (which are not involved in the building up models) is good. Structural indicators (alerts) for increase and decrease of the anti-malaria activity are defined.     

Energetically important C-H···F-C pseudohydrogen bonding in water: evidence and application to rational design of oligonucleotides with high binding affinity

It is controversial whether organic fluorine can form energetically important hydrogen bonds in aqueous environments. We previously showed by NMR and molecular modeling that the unexpectedly high binding affinity of 2'F-ANA is largely due to a C-H···F-C pseudohydrogen bond at pyrimidine-purine steps. Comparisons of the melting of duplexes with identical sequence composition but a rearranged sequence confirm that energetically important fluorine-mediated pseudohydrogen bonding is in operation in these sequences. The effect is of particular importance when the H-bond donor (purine H8) is activated by the presence of fluorine at its own 2'-position. These results provide a rational method to increase the binding affinity of antisense oligonucleotides by placement of 2'F-ANA modifications at pyrimidine-purine steps.     

Ratios of substrates and inhibitors of prostaglandin synthesis in blood plasma of atients with heart ischemia

To check the proposed hypothesis that the relative content of individual polyunsaturated fatty acids (PUFAs)—substrates and inhibi tors of prostanoid synthesis—in plasma can be regarded as a quantita tive risk factor of blood clotting, a test was conducted on free fatty acids content in blood plasma of healthy people (group 0) and patients with heart ischemia before (group 1) and after (group 2) they were treated for a month with a food additive called “Eiconol,” enriched with PUFA ω3. Different proportions of PUF As have been calculated in all cases, accounting for the contribution of each acid to the process of primary clotting. Comparison of PUFA rations among the three groups showed significant differences of means between groups 0 and 1 and also group 1 and 2 for 6 out of 7 proposed coefficients, which disappeared after “Eiconol” treatment (comparison of groups 0 and 2). The results led to the conclusion that out of the proposed PUFA proportions, the coefficients describing the relative content of arachidonic acid in blood plasma may be the most informative for diagnosis and treatment efficiency in evaluation of heart and vascular diseases.     

Comparison of QSAR models of anti-HIV-1 potencies based on labeled hydrogen filled graph and graph of atomic orbitals

Quantitative structure–activity relationships of anti-HIV-1 potencies of compounds, known as TIBO and HEPT derivatives, have been obtained by means of the optimization of correlation weights of local graph invariants (OCWLGI). Based on OCWLGI, Morgan-extended connectivity in labeled hydrogen-filled graph (LHFG) and in graph of atomic orbitals (GAO) have been used. The GAO may be obtained from the LHFG. Vertices in GAO are images of atomic orbitals such as the 1s¹, 2p², 3d³, etc. Comparison of the OCWLGI models of the anti-HIV-1 potencies based on LHFGs and OCWLGI models of mentioned endpoint based on the GAO has shown that the GAO models are better than the LHFG models.     

Thermal fragmentation and rearrangement of N-arylbenzamidoxime and O-phenylsulfonyloxime derivatives

Thermal fragmentation of N-arylbenzamide oximes I, II (Ar = Ph, p-tolyl) under nitrogen gives rise to benzanilide and 2-phenylbenzoxazole as the major products, in addition to benzonitrile, arylamines, phenols, benzoic acid, o- and p-aminophenols and benzimidazole derivatives. In the presence of naphthalene as radical scavenger, I gave - and β-naphthols beside the previous products. Also, heating N-arylbenzamide O-phenylsulfonyloximes III under reflux in boiling tetralin lead to the formation of benzonitrile, arylamines, diphenylamine, benzenesulfonic acid, diphenyl sulfone, 1-hydroxytetralin, -tetralone, and 1,1′-bitetralyl as the major products. Analogous results are obtained on heating III in the presence of isoquinoline as a radical trap which formed 1-phenylisoquinoline. The isolated products have been interpreted in terms of a free radical mechanism involving the homolysis of NO and/or CN bonds.     

New α-substituted alkylbenzene- and dialkylbenzene-1,2-diphosphonates: side-chain metalation of tetraethyl 4-methyl- and 4,5-dimethylbenzene-1,2-diphosphonates

Carbocyclic 1,2-diphosphonates (1a, 1b) are prepared by the Diels-Alder reaction of classical donor alka-1,3-dienes (isoprene and 2,3-dimethyl-1,3-butadiene) with tetraethyl acetylene bisphosphonate. Their aromatization by the KMnO₄-Al₂O₃ system affords 4-methyl and 4,5-dimethylbenzene-1,2-diphosphonates (2a, 2b), used as precursor for the generation of benzyl-type carbanions (3a, 3b) by lithiation with lithium isopropylamide in THF at −80 °C. The carbanions react with electrophilic reagents (chlorotrimethylsilane, p-fluorobenzaldehyde, and ethyl trifluoroacetate) in situ to form corresponding α-substituted monoalkyl- and dialkylbenzenediphosphonates in good yields.     

Pressure-induced magnetic switching and linkage isomerism in K0.4Fe4[Cr(CN)6]2.8 x 16 H2O: X-ray absorption and magnetic circular dichroism studies

The effect of applied pressure on the magnetic properties of the Prussian blue analogue K0.4Fe4[Cr(CN)6]2.8 x 16 H2O (1) has been analyzed by dc and ac magnetic susceptibility measurements. Under ambient conditions, 1 orders ferromagnetically at a critical temperature (T(C)) of 18.5 K. Under application of pressure in the 0-1200 MPa range, the magnetization of the material decreases and its critical temperature shifts to lower temperatures, reaching T(C) = 7.5 K at 1200 MPa. Pressure-dependent Raman and Mossbauer spectroscopy measurements show that this striking behavior is due to the isomerization of some Cr(III)-C[triple bond]N-Fe(II) linkages to the Cr(III)-N[triple bond]C-Fe(II) form. As a result, the ligand field around the iron(II) centers increases, and the diamagnetic low-spin state is populated. As the number of diamagnetic centers in the cubic lattice increases, the net magnetization and critical temperature of the material decrease considerably. The phenomenon is reversible: releasing the pressure restores the magnetic properties of the original material. However, we have found that under more severe pressure conditions, a metastable sample containing 22% Cr(III)-N[triple bond]C-Fe(II) linkages can be obtained. X-ray absorption spectroscopy and magnetic circular dichroism of this metastable sample confirm the linkage isomerization process.     

The use of phosphine ligands to control the regiochemistry of Pd-catalyzed hydrostannations of 1-alkynes: synthesis of (E)-1-tributylstannyl-1-alkenes

The regiochemistry of palladium-catalyzed hydrostannations of terminal alkynes is dramatically influenced by ligand effects. Use of phosphines such as Cy3P, t-Bu2PCH2t-Bu, and t-Bu3P provides (E)-1-tributylstannyl-1-alkenes with regioselectivities up to >99:<1 for substrates where the commonly used Ph3P shows much lower regioselectivities.