Ionic mass transfer at rotating electrodes formed by solids of revolution : Rotating one-base spherical segment electrodes

The ionic mass transfer at rotating electrodes formed by a one-base spherical segment has been experimentally studied by the usual electrochemical methods. For electrodes which involve an electrochemical active area having angle up to 40 deg, the mass-transfer rate equation is [fórmula en el documento].Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Ionic mass transfer in channel electrodes under laminar flow

The rate of ionic mass tranfer under a Poiseuille profile in channel electrodes involving inert zones has been studied. The electrolysis cell was vertically and horizontally placed, the working electrodes facing either upwards or downwards. An extension of Levich's solution for the convective-diffusion equation in a tube comprising an inert zone was applied. The experimental numerical coefficient lies 10% lower than the one theoretically derived.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Phase-conjugation of the isolated optical vortex using a flat surfaces

The robust method for obtaining the helical interference pattern due to the phase-conjugation of an isolated optical vortex by means of the non-holographic technique is proposed. It is shown that a perfect wavefront-reversal of the vortex in a linear polarization state via even number of reflections is achievable due to the turn of the photon's momentum $\vec p \approx \hbar \vec k$ with respect to the photon's orbital angular momentum projection $L_z$. The possible experimental realization is based upon $catseye-prism$ like reflections inside the confocal optical $loop$ cavity. The alternative scheme contains the Dove prism embedded in the optical $loop$ with the odd number of reflections from mirrors. This $confocal$ interferometric technique is applicable to the optical tweezers, atomic traps, Sagnac laser loops and metamaterials fabrication.Comment: 4 pages, 3 figures, submitted to referred journa

Kinetics and growth modes of quasi-2d silver branched electrodeposits produced in the presence of a supporting electrolyte

Quasi-2d silver electrodeposits were grown electrochemically at constant potential from aqueous Ag+ ion-containing solutions in the presence of a supporting electrolyte, at room temperature, using a three-electrode quasi-2d circular electrochemical cell. Open branching and dense radial branching patterns were distinguished on the centimetre scale, and growth mode transitions could be observed during the process. Branching patterns exhibited a mass fractal behaviour with a mass fractal dimension increasing from that expected for a DLA-like pattern to that of a dense branching pattern as either the cathodic overpotential (ηc) or the Ag+ ion concentration in the solution (c) was increased. The electrodeposition current increased with time exhibiting different regimes depending on whether an open branching or a dense radial branching growth mode prevailed. When the electrodeposition time exceeded a certain critical value, the radial growth rate of electrodeposits (vr) approached a vr α ηcc relationship. The experimental morphologies and growth kinetics were reproduced by Monte Carlo simulations of a growth model in which depositing particles follow a biased random walk.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Growth of three-dimensional silver fractal electrodeposits under damped free convection

Quasispherical three-dimensional Ag electrodeposits grown at constant potential and damped free convection exhibit a quasi-isotropic radial growth up to a critical radius rc≃0.3 cm and a mass fractal dimension DM=2.5. For r≫rc, DM→3. The product vrη’ is nearly constant, vr being the radial growth velocity, and η’ the apparent medium viscosity. It appears that vr is determined by the Laplacian field operating between cathode and anode.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Ionic mass transfer at rotating electrodes formed by solids of revolution : Rotating one-base spherical segment electrodes

The ionic mass transfer at rotating electrodes formed by a one-base spherical segment has been experimentally studied by the usual electrochemical methods. For electrodes which involve an electrochemical active area having angle up to 40 deg, the mass-transfer rate equation is [fórmula en el documento].Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Ionic mass transfer in channel electrodes under laminar flow

The rate of ionic mass tranfer under a Poiseuille profile in channel electrodes involving inert zones has been studied. The electrolysis cell was vertically and horizontally placed, the working electrodes facing either upwards or downwards. An extension of Levich's solution for the convective-diffusion equation in a tube comprising an inert zone was applied. The experimental numerical coefficient lies 10% lower than the one theoretically derived.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

GLP-1 Mediates Regulation of Colonic ACE2 Expression by the Bile Acid Receptor GPBAR1 in Inflammation

Background & Aims: ACE2, a carboxypeptidase that generates Ang-(1-7) from Ang II, is highly expressed in the lung, small intestine and colon. GPBAR1, is a G protein bile acid receptor that promotes the release of the insulinotropic factor glucagon-like peptide (GLP)-1 and attenuates intestinal inflammation. Methods: We investigated the expression of ACE2, GLP-1 and GPBAR1 in two cohorts of Crohn’s disease (CD) patients and three mouse models of colitis and Gpbar1−/− mice. Activation of GPBAR1 in these models and in vitro was achieved by BAR501, a selective GPBAR1 agonist. Results: In IBD patients, ACE2 mRNA expression was regulated in a site-specific manner in response to inflammation. While expression of ileal ACE2 mRNA was reduced, the colon expression was induced. Colon expression of ACE2 mRNA in IBD correlated with expression of TNF-α and GPBAR1. A positive correlation occurred between GCG and GPBAR1 in human samples and animal models of colitis. In these models, ACE2 mRNA expression was further upregulated by GPABR1 agonism and reversed by exendin-3, a GLP-1 receptor antagonist. In in vitro studies, liraglutide, a GLP-1 analogue, increased the expression of ACE2 in colon epithelial cells/macrophages co-cultures. Conclusions: ACE2 mRNA expression in the colon of IBD patients and rodent models of colitis is regulated in a TNF-α-and GLP-1-dependent manner. We have identified a GPBAR1/GLP-1 mechanism as a positive modulator of ACE2

The Standard Model in Strong Fields: Electroweak Radiative Corrections for Highly Charged Ions

Electroweak radiative corrections to the matrix elements $<ns_{1/2}|{\hat H}_{PNC}|n'p_{1/2}>$ are calculated for highly charged hydrogenlike ions. These matrix elements constitute the basis for the description of the most parity nonconserving (PNC) processes in atomic physics. The operator ${\hat H}_{PNC}$ represents the parity nonconserving relativistic effective atomic Hamiltonian at the tree level. The deviation of these calculations from the calculations valid for the momentum transfer $q^{2}=0$ demonstrates the effect of the strong field, characterized by the momentum transfer $q^{2}=m_{e}^{2}$ ($m_{e}$ is the electron mass). This allows for a test of the Standard Model in the presence of strong fields in experiments with highly charged ions.Comment: 27 LaTex page