Catalytic Enantioselective β-Alkylation of α,β-Unsaturated Aldehydes by Combination of Transition-Metal- and Aminocatalysis: Total Synthesis of Bisabolane Sesquiterpenes

Branching out! The first co-catalytic enantioselective (up to 98:2 e.r.) β-alkylation of α,β-unsaturated aldehydes by combination of simple chiral amine and copper catalysts provides β-branched aldehydes in a one-pot protocol. The methodology was applied to the short total syntheses of bisabolane sesquiterpenes (S)-(+)-curcumene, (E)-(S)-(+)-3-dehydrocurcumene and (S)-(+)-tumerone.     

Porphyrin dye-sensitised solar cells utilising a solid-state electrolyte

We describe a porphyrin dye-sensitised solar cell utilising a solid state electrolyte containing the I(-)/I(3)(-) redox couple, which yields a performance of 5.3% under moderate light intensity and 4.8% at full sun.     

Application of Black Pearl carbon-supported WO3 nanostructures as hybrid carriers for electrocatalytic RuSex nanoparticles

RuSe_x electrocatalytic nanoparticles were deposited onto hybrid carriers composed of Black Pearl carbon-supported tungsten oxide; and the resulting system's electrochemical activity was investigated during oxygen reduction reaction. The tungsten oxide-utilizing and RuSe_x nanoparticle-containing materials were characterized using transmission electron microscopy, X-ray diffraction and electrochemical diagnostic techniques such as cyclic voltammetry and rotating ring-disk voltammetry. Application of Black Pearl carbon carriers modified with ultra-thin films of WO₃ as matrices (supports) for RuSe_x catalytic centers results during electroreduction of oxygen in 0.5 mol dm⁻³ H₂SO₄ (under rotating disk voltammetric conditions) in the potential shift of ca. 70 mV towards more positive values relative to the behavior of the analogous WO₃-free system. Also the percent formation (at ring in the rotating ring-disk voltammetry) of the undesirable hydrogen peroxide has been decreased approximately twice by utilizing WO₃-modified carbon carriers. The results are consistent with the bifunctional mechanism in which oxygen reduction is initiated at RuSe_x centers and the hydrogen peroxide intermediate is reductively decomposed at reactive WO₃-modified Black Pearl supports. The electrocatalytic activity of the system utilizing WO₃-modified Black Pearl supports has been basically unchanged upon addition of acetic acid, formic acid or methyl formate to the sulfuric acid supporting electrolyte.     

Mechanisms of Non-Newtonian Polymer Flow Through Porous Media Using Navier–Stokes Approach

This study includes solving non-Newtonian Navier–Stokes equation in three-dimensions (real rock images) and two-dimensions (simplified pore geometries) using the finite-difference method. The purpose of this study is to improve understanding of local phenomena leading to the mobilization of residual oil. This involves local pressure variations for non-Newtonian polymers and compares it with Newtonian fluid behavior. When a higher degree of shear thickening is induced, more flow diversion to side channels perpendicular to the main flow path and larger drag on fluids inside side channels will occur. This is consistent with oil mobilization and lowering of residual oil saturation.     

New trends in the electrochemical sensing of dopamine

Since the early 70s electrochemistry has been used as a powerful analytical technique for monitoring electroactive species in living organisms. In particular, after extremely rapid evolution of new micro and nanotechnology it has been established as an invaluable technique ranging from experiments in vivo to measurement of exocytosis during communication between cells under in vitro conditions. This review highlights recent advances in the development of electrochemical sensors for selective sensing of one of the most important neurotransmitters—dopamine. Dopamine is an electroactive catecholamine neurotransmitter, abundant in the mammalian central nervous system, affecting both cognitive and behavioral functions of living organisms. We have not attempted to cover a large time-span nor to be comprehensive in presenting the vast literature devoted to electrochemical dopamine sensing. Instead, we have focused on the last five years, describing recent progress as well as showing some problems and directions for future development.     

Determination of the Sedimentation Coefficient-Mol ecular Weight Relation for Nonideal Systems Based on Sedimentation and Viscosity Measurements of a Few Unfractionated Samples

A new method for the determination of the sedimentation coefficient-molecular weight relation is proposed. Based on the very low sensitivity of the corresponding sedimentation coefficient average S _0,1 and the weight-average molecular weight M _w (calculated according to the generalized Flory-Mandelkern equation) to changes of the a parameter, the S_0,1 and M _w values are estimated from constant initial values of the a_s parameter for all those polymer-solvent systems for which the real a_s values do not exceed the interval 0.3-0.5. The approximations involved give an error lower than 8.5%, Le., below the experimental errors of the M_w values determined for polydiSDerse samDles. The new method of determining the S_o -M relation was applied to the system styrene-acrylonitrile copolymer (22.6-wt%_oacrylonitrile content) in acetone at 25°C and yielded the following relation: S₀=2.90 × 10 ^?15 M ^0,49 sec. Although in the case of this polymer-solvent system the a value of 0.49 is close to the one corresponding to θ systems, the method is shown by model calculations to be of general applicability and especially useful in the case of nonideal polymer-solvent systems.