Studies on ion association. Calorimetric study of the formation of monoazido complexes of Ni(II), Zn(II) and Cd(II)

From rehydration experiments the hydrates Ba(OH)₂ · 8 H₂O, Ba(OH)₂ · 3 H₂O β-Ba(OH)₂, · 1 H₂O, and γ-Ba(OH)₂ · 1 H₂O have been found in the system Ba(OH)₂-H₂O. Thermoanalytical measurements (DTA, TG, DTG, high temperature X-ray diffraction, high temperature Raman scattering) on these hydrates are reported. Thermal decomposition of Ba(OH)₂ · 8 H₂O and Ba(OH)₂ · 3 H₂O always results in the formation of β-Ba(OH)₂ · 1 H₂O, the stable form of the monohydrates at ambient temperature. Dehydration of β- and γ-Ba(OH)₂ · 1 H₂O, both of which form anhydrous β-Ba(OH)₂ as the first product of decomposition, starts at 105 and 115°C, respectively. Single crystals of Ba(OH)₂ · 3 H₂O and γ-Ba(OH)₂ · 1 H₂O were prepared from Ba(OH)₂ · 8 H₂O meltings and from ethanolic solutions of Ba(OH)₂ , respectively. The crystal data are: Ba(OH)₂ · 3 H₂O (orthorhombic, Pnma): a = 764.0(2), b = 1140,3(5), c = 596.5(1) pm, Z = 4; γ-Ba(OH)₂ · 1 H₂O (monoclinic, P2₁/m or P2₁): a = 704.9(2), b = 418.4(1), c = 633.3(1) pm, β = 111.45(2)°, Z = 2.     

A Cylindrical Waveguide Structure with Helical Grooves for High Power TWTs

In this work, the field analysis of a cylindrical interaction structure, with helical grooves, and an inner dielectric lining for possible employment in high power TWT amplifiers in the conventional slow-wave regime, is presented. The Ohmic dominance of the microwave power on the walls of this propagating circuit is deduced.     

Steric-effect induced alterations in streaming potential and energy transfer efficiency of non-newtonian fluids in narrow confinements

In this work, we explore the possibilities of utilizing the combined consequences of interfacial electrokinetics and rheology toward augmenting the energy transfer efficiencies in narrow fluidic confinements. In particular, we consider the exploitation of steric effects (i.e., effect of finite size of the ionic species) in non-Newtonian fluids over small scales, to report dramatic augmentations in the streaming potential, for shear-thickening fluids. We first derive an expression for the streaming potential considering strong electrical double layer interactions in the confined flow passage and the consequences of the finite conductance of the Stern layer, going beyond the Debye-Hu?ckel limit. With a detailed accounting for the excluded volume effects of the ionic species and their interaction with pertinent interfacial phenomena of special type of rheological fluids such as the power law fluids in the above-mentioned formalism, we demonstrate that a confluence of the steric interactions with the non-Newtonian transport characteristics may result in giant augmentations in the energy transfer efficiency for shear-thickening fluids under appropriate conditions.     

Ionic size dependent electroosmosis in ion‐selective microchannels and nanochannels

Electrokinetics in salt‐free media (in which counterions are only present) is central to the performance of many systems of modern technological relevance, ranging from ion‐selective nanopores to electronic papers. Here, we introduce an analytical theory to describe the size dependence of electroosmosis in such typical scenarios, exhibiting an interesting confluence of the implications of interdependence of the electroosmotic transport mechanisms, ionic sizes, and confinement dimensions along with the counterion concentration. Our results do reveal that the concerned mobility parameter, describing the strength of electroosmotic transport, increases simultaneously with increments in the surface charge density as well as an ionic size factor (also known as the steric factor), bearing far‐ranging consequences in microfluidic and nanofluidic technology.     

Mechanistic Studies on the Oxidation of Hydrazine by Tris(biguanide)manganese(IV) in Aqueous Acidic Media

The title Mn^IV complex, [Mn(LH₂)₃]⁴⁺ (LH₂ = biguanide = H₂NC(NH)NHC(NH)NH₂), an authentic two‐electron oxidant, quantitatively oxidizes hydrazine (H₂NNH₂) to dinitrogen in the pH interval 2.00–3.50. The net four‐electron oxidation of hydrazine is provided by two Mn^IV as established by stoichiometric studies. The overall reaction is composed of two parallel paths:     

Hydrodynamic Dispersion and Lamb Surfaces in Darcy Flow

Transport in Porous Media - Transport processes such as the dispersion and mixing of solutes are governed by the interplay of advection and diffusion, where advection acts to organise fluid...     

Reductions by titanium(II) as catalyzed by titanium(IV)

The cobalt(III) complexes, [(NH3)5CoBr]2+ and [(NH3)5CoI]2+ are reduced by Ti(II) solutions containing Ti(IV), generating nearly linear (zero-order) profiles that become curved only during the last few percent of reaction. Other Co(III)-Ti(II) systems exhibit the usual exponential traces with rates proportional to [Co(III)]. Observed kinetics of the biphasic catalyzed Ti(II)-Co(III)Br and Ti(II)-Co(III)I reactions support the reaction sequence: [Ti(II)(H20)n]2+ + [Ti(IV)F5]- (k1)<==>(k -1) [Ti(II)(H2O)(n-1)]2+ + [(H2O)Ti(IV)F5]-, [Ti(II)(H2O)(n-1)]2+ + Co(III) (k2)--> Ti(III) + Co(II) with rates determined mainly by the slow Ti(IV)-Ti(II) ligand exchange (k1 = 9 x 10(-3) M(-1) s(-1) at 22 degrees C). Computer simulations of the catalyzed Ti(II)-Co(III) reaction in perchlorate-triflate media yield relative rates for reduction by the proposed active [Ti(II)(H2O)(n-1)]2+ intermediate; k(Br)/k(I) = 8.     

Explaining GRB in the light of energy deposition rate for v+ [`(n)] \bar \nu → e+ + e? in a compact star

We have studied the v+ $ \bar \nu $ \bar \nu → e ⁺ + e ⁻ energy deposition rate near a rotating compact star which is important for the study of gamma ray bursts (GRB). The General relativistic (GR) and rotational effects increase the efficiency of the process immensely. The rotational effect also brings about an asymmetry in the deposition rate of the star.     

Kinetics and mechanism of oxidation of iodide with a (μ‐oxo)diiron(III,III) complex in weakly acidic media

The complex ion [Fe^III₂(μ‐O)(phen)₄(H₂O)₂]⁴⁺ ( 1 ) (phen = 1,10‐phenanthroline) and its hydrolytic derivatives [Fe^III₂(μ‐O)(phen)₄(H₂O)(OH)]³⁺ ( 1a ) and [Fe^III₂(μ‐O)(phen)₄‐ (OH)₂]²⁺ ( 2a ) coexist in rapid equilibria in the range pH 4.23–5.35 in the presence of excess phenanthroline (pK_a1 = 3.71±0.03, pK_a2 = 5.28± 0.07). The solution reacts quantitatively with I⁻ to produce [Fe(phen)₃]²⁺ and I₂. Only 1 but none of its hydrolytic derivatives is kinetically active. Both inner and outer sphere pathways operate. The observed rate constants show second‐order dependence on the concentration of iodide, while the dependence on [H⁺] is complex in nature. Added Cl⁻ inhibits the formation of adduct with I⁻ and thus retards the rate of inner sphere path, leading to a rate saturation at high [Cl⁻], where only the outer sphere mechanism is active. Kinetic data indicate that simultaneous presence of two I⁻ in the vicinity of diiron core is necessary for the reduction of 1 . © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 737–743, 2005