Calculation of the potential of interaction of excited atoms of alkali elements with a mercury atom: A-Hg interaction (A=K,Fr)

The interatomic potentials in the system (alkali atom in the ground and excited states)—((mercury atom) are calculated on the basis of the effective pseudopotential method using a new form of the polarized interaction potential obtained from calculations of the most important polarization patterns of perturbation theory in the Thomas-Fermi approximation. This method is used to calculate the intermolecular terms of the system A-Hg (A=K, Fr), some of which have been obtained previously.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 84–88, January, 1996.     

Molecular Dynamics Simulations of Proteins with Chemically Modified Disulfide Bonds

Proteins that are used as therapeutic drugs act in the extracellular microenvironment. They usually have a small number of intramolecular disulfide bonds to help maintain their tertiary structure in the vascular circulation. In general, most cysteine residues are part of a disulfide bond with free sulfhydrals being uncommon. We have studied whether the site-specific chemical reduction of disulfides and the incorporation of a 3-carbon methylene bridge between the cysteines in interferon-α 2a would change the structure of this protein. Bridging of both of the disulfide bonds of interferon-α 2a was studied using two different molecular simulation protocols: (1) molecular dynamics, and (2) stochastic dynamics. We have shown that the disulfide bonds in interferon-α 2a can be reduced and chemically modified without significantly altering the tertiary structure of the protein. This offers the novel possibility of chemically modifying therapeutically important proteins without affecting their biological properties.     

A Cascade Strategy Enables a Total Synthesis of (±)‐Morphine

Morphine has been a target for synthetic chemists since Robinson proposed its correct structure in 1925, resulting in a large number of total syntheses of morphine alkaloids. Here we report a total synthesis of (±)‐morphine that employs two key strategic cyclizations: 1) a diastereoselective light‐mediated cyclization of an O‐arylated butyrolactone to form a tricyclic cis‐fused benzofuran and 2) a cascade ene–yne–ene ring closing metathesis to forge the tetracyclic morphine core. This approach enables a short and stereoselective synthesis of morphine in an overall yield of 6.6 %.     

State-space exact linearization and stabilization with feedback control in SODE economic models

The paper presents a non-conventional control engineering strategy proposed by experimental physicists, employed for controlling Dynamical Systems and basically designed for the control of nonlinear systems (Liqun and Yan Zhu in Appl. Math. Mech. 19:67–73, 1998; Liqun and Yan Zhu in Phys. Lett. A 262:350–354, 1999). After a brief presentation of the strategy—called state space exact linearization method, this is applied to design a nonlinear feedback control law as well as a modified version of this law, to control the Kaldor (Chang and Smyth in Rev. Econ. Stud. 38:37–44, 1971) and the Bonhoeffer-Van Der Pohl (Grassman in Environment, Economics and their Mathematical Models, 1994) nonlinear systems used in macro-economic business cycles.     

Further shortening of the C-C single bond in substituted tetrahedranyl tetrahedrane systems: an energy decomposition analysis

The computational study explores the electronic fine tuning of the exocyclic C-C single bond length in tetrahedranyl tetrahedrane as a function of various substituents. The factors which determine the bond lengths and bond strengths are examined by using the EDA method.     

Chemically-enabled synthesis of 1,2,3,4-tetrahydroisoquinolin-1-ones

We have developed a number of efficient protocols for the facile synthesis of 1,2,3,4-tetrahydroisoquinolin-1-ones. This synthetic methodology allowed concise and efficient exploration of the SAR in all areas of the molecule. A number of these methods proved to be versatile, efficient and amenable to parallel synthesis.     

A new diamine containing disiloxane moiety and some derived Schiff bases: synthesis,structural characterisation and antimicrobial activity

A new siloxane diamine, 1,3-bis(amino-phenylene-ester-methylene)tetramethyldisiloxane (1), was obtained by a two-step procedure and used to prepare a series of Schiff bases (2–5), by reaction with different carbonylic compounds: salicylaldehyde, 3,5-dibromosalicylaldehyde, 5-chlorosalicylaldehyde and 3,5-di-tert-butyl-2-hydroxybenzaldehyde. All compounds, separated in crystalline form, were characterised by spectral (FTIR, UV–vis and NMR) analysis as well as by single-crystal X-ray diffraction. In these structures, different packing motifs occur depending on the different association degree determined by intra- and intermolecular π–π stacking interactions. Antimicrobial activity of the compounds was evaluated against three fungi and two bacteria, where the Schiff bases derived from salicylaldehyde and in special 5-chlorosalicylaldehyde showed remarkable activity.     

Rheological characterization of complex fluids in electro-magnetic fields

The paper is focused on the experimental investigations and rheological characterisations in magnetic and electric fields of liquids based on water in crude oils emulsions, added with ferrofluids (two types of crude oils are used in experiments: asphaltic and paraffinic, respectively). The final samples disclose weakly effects in the presence of magnetic field (saturated magnetization: M_n < 300 [G]) and behave almost as isolators in electric field (conductivity: σ < 10⁻⁵ [S/m]). The main goal of the study is to explore to what extent rheometry of complex fluids in electric and magnetic fields is able to offer value information about the internal structure of the samples. The experimental results prove that anomalous rheological behaviour (thixotropy, non-monotonic flow curve or viscosity function) of a complex fluid (in our case, emulsions based on paraffinic oil) generate also thixotropic properties and non-monotonic answers in the presence ferrofluids, under low magnetic and/or electric fields intensity. Our prospective study suggests that novel experimental procedures based on interaction: electro-magnetic field–complex fluids can be developed, in order to determine indirectly some relevant rheological properties of the complex fluids with internal network structure.     

Determination of the non-linear parameter (mobility factor) of the Giesekus constitutive model using LAOS procedure

The paper introduces a novel procedure to determine the non-linear parameter of the Giesekus model, in relation to the characterization of the non-linear oscillatory shear regime of viscoelastic polymer solutions based on polyacrylamide. Instead of using the shear-thinning viscosity as the representative non-linear effect, the third harmonic in the Fourier spectrum of the shear stress response signal is considered for computing the mobility factor. The fluid is subjected to large amplitude oscillatory shear (LAOS) and its response is recorded. Deviations of this signal from the sinusoidal form are specific to each material and gives both qualitative and quantitative measures of the non-linearity. By fitting the material response with the corresponding numerical solutions of the n-modes Giesekus constitutive relation, one can extract the values of the non-linear α_i-parameters that describe the fluid rheology. It is demonstrated that this procedure, which can be successfully applied to semi-concentrated polymer solutions, provides better results than the classical viscosity-fit method.