Experimental and theoretical study of the onset of the growth of an irregular metal electrodeposit

Electrodeposition of a metal can produce aggregates with very irregular morphologies, in particular dendrites. In order to better understand these phenomena, we studied the preliminary stage of copper growth from copper sulfate by in situ optical experiments and impedance spectroscopy. Experiments were performed in a thin layer cell put in a vertical position, with cathode on top. Using a vertical cell instead of a horizontal one tends to stabilize the electrochemical system. The concentration measured by optical absorption is in agreement with theoretical prediction at the onset of polarization. Close to the limiting current density, oscillations were observed in the cell voltage. Impedance spectra could be fitted either using a simple equivalent circuit at low current density, or more complex calculations at high current density.     

Optimization of molybdenum thin films for electrodeposited CIGS solar cells

Molybdenum thin films are widely used as back contact for CIGS-based solar cells. In this paper, the properties of Mo layers deposited by DC and RF sputtering are investigated in view of a specific optimization of electrodeposited CIGS solar cells. In the first part of the paper RF and DC films are grown on soda lime glass, in a pressure range from 2 to 20 mTorr, and for various RF power and DC current. They are then characterized by optical, electrical and structural methods. It appears that the films deposited by RF mode sputtering are more reflective, conductive and adherent than those obtained by DC mode. Structurally, they present different behaviors with respect to nucleation and growth of CIGS precursor layers by electrodeposition. A large difference is observed in the photovoltaic properties of completed cells, with much better performances obtained with DC Mo layers.     

Coupling of MALDI-TOF mass analysis to the separation of biotinylated peptides by magnetic streptavidin beads

Extraction of biotinylated peptides by streptavidin magnetic beads has been directly coupled to the MALDI-TOF mass analysis. The elution of peptides from the beads is achieved by first mixing the beads with the MALDI matrix solution and removing, after a few minutes, the beads with a magnet; then, the matrix solution containing the biotinylated peptide is directly mass analyzed by MALDI. Three examples are presented to show the capabilities of this procedure to detect biotinylated peptides present at very low concentrations in complex mixtures. Detection limits of less than 100 finol can be achieved. Such a coupling strategy is of great interest to investigate peptide/ protein interactions.     

Electrochemical investigation of the autocatalytic deposition of Ni-Cu-P alloys

Autocatalytic deposition of Ni-Cu-P alloys (55-65 wt % Ni, 25-35 wt % Cu, 7-10 wt %P) has been carried out. It is shown that the hypophosphite concentration must be higher than a certain threshold to induce the autocatalytic process. The impedance behaviour exemplifies the kinetic evolution: a large capacitive loop with a high-frequency inflection when only chemical displacement occurs and two well-defined capacitive features when the autocatalytic process is achieved. Mutual interactions occur between partial oxidation and reduction reactions which are both depolarized as compared to the separate reactions. In addition, phosphorus incorporation is always reduced when the copper content increases. A pH increase accelerates the plating process though it inhibits the cathodic discharge and reduces the copper content.     

Étude de la conductibilité électrique de couches minces de chrome préparées par évaporation thermique. Détermination du libre parcours moyen et de la densité des électrons de conduction

The electrical conductivity of chromium thin films evaporated in vacuum on glass substrates is explained by means of a simple model which enables the mean free path and the density of the conduction electrons in chromium to be determined. It is supposed that the films are composed of agglomerates connected by metallic bridges and that the lateral dimensions of the agglomerates are constant for thicknesses between 50 and 1600 Å, whereas the height is equal to that of the film. Taking into account the variation of the resistivity of the films due to adsorption of the residual gases of the vacuum chamber and applying Fuchs-Sondheimer's theory, values for the mean free path and the density of the conduction electrons in bulk chromium are obtained, respectively equal to 320 Å and 5.3 × 10²¹ electrons/cm³.     

Electrochemical reduction of ZrCl4 in molten NaCl,CsCl and KCl-LiCl and chemical reactions coupled to the electrodeposition of zirconium

Cyclic voltammetry is used to study the reduction of ZrCl₄ in molten NaCl, KCl-LiCl or CsCl and the nature of the various electrochemical processes. The chemical reactions between Zr metal and the M₂ZrCl₆ complex occurring in the bath are also studied.     

Use of conformationally constrained peptides for a topographical analysis of the combing site of a monoclonal anti-substance P antibody

We studied the trends from 1969 to the mid-1980s in the incidence and mortality of acute myocardial infarction and stroke in Swedish women residing in the Uppsala Health Care Region. We used data from the Inpatient Care and Causes of Death registers to obtain total first event incidence and mortality rates. In our population, there were 20,182 acute myocardial infarctions and 30,462 stroke events, and 17,359 and 21,336 deaths, respectively. We found an average overall annual increase of 1.3% in the age-standardized incidence of acute myocardial infarction during the 1970s, followed by decreasing rates during the early 1980s. Mortality was virtually unchanged. Notably, among women 45-49 years of age, we observed a rising trend during the whole period, whereas in the oldest age groups, the increase slowed and reversed in the latter years. Both the incidence and mortality for stroke declined steadily: the age-standardized incidence fell by an average of 2.1% per year for all stroke and 7.8% for intracerebral hemorrhage. The falling rate of stroke was best explained by birth cohort effects, with a 30% reduction in women born in 1920 and later as compared with those born in 1890. We conclude that important changes in Swedish women's cardiovascular health have taken place and that increasing cigarette smoking and hypertensive treatment are major determinants.     

Electrodeposition of Ni-Mo alloys with pulse reverse potentials

With the aim of improving the protective properties of Ni-Mo alloy layers, pulse reverse electro-deposition has been investigated. The anodic pulses were applied in the potential range where hydrogen desorption and oxidation occur. The alloy composition was shown to depend on the pulse parameters, especially on the anodic pulse duration. For long anodic pulses a preferential dissolution of molybdenum in the electrodeposited alloy occurs, while bulk Ni-Mo alloys do not undergo any dissolution. For anodic pulses longer than a certain threshold the electrocrystallization process becomes blocked. The morphology and microstructure of the layers are mainly determined by the molybdenum content rather than by the pulse parameters.     

The Efficacies of Cell‐Penetrating Peptides in Accumulating in Large Unilamellar Vesicles Depend on their Ability To Form Inverted Micelles

In this study, the direct translocation of cell‐penetrating peptides (CPPs) into large unilamellar vesicles (LUVs) was shown to be rapid for all the most commonly used CPPs. This translocation led within a few minutes to intravesicular accumulation up to 0.5 mM , with no need for a transbilayer potential. The accumulation of CPPs inside LUVs was found to depend on CPP sequence, CPP extravesicular concentration and phospholipid (PL) composition, either in binary or ternary mixtures of PLs. More interestingly, the role of anionic phospholipid flip‐flopping in the translocation process was ascertained. CPPs enhanced the flipping of PLs, and the intravesicular CPP accumulation directly correlated with the amount of anionic PLs that had been transferred from the external to the internal leaflet of the LUV bilayer, thus demonstrating the transport of peptide/lipid complexes as inverted micelles.     

Effects of quinidine, verapamil, nifedipine and ouabain on hysteresis in atrial refractoriness in the conscious dog: an approach to ionic mechanisms

Active transport between nucleus and cytoplasm proceeds through nuclear pore complexes (NPCs) and is mediated largely by shuttling transport receptors that use direct RanGTP binding to coordinate loading and unloading of cargo [1] [2] [3] [4]. Import receptors such as importin beta or transportin bind their substrates at low RanGTP levels in the cytoplasm and release them upon encountering RanGTP in the nucleus, where a high RanGTP concentration is predicted. This substrate release is, in the case of import by the importin alpha/beta heterodimer, coupled directly to importin beta release from the NPCs. If the importin beta -RanGTP interaction is prevented, import intermediates arrest at the nuclear side of the NPCs [5] [6]. This arrest makes it difficult to probe directly the Ran and energy requirements of the actual translocation from the cytoplasmic to the nuclear side of the NPC, which immediately precedes substrate release. Here, we have shown that in the case of transportin, dissociation of transportin-substrate complexes is uncoupled from transportin release from NPCs. This allowed us to dissect the requirements of translocation through the NPC, substrate release and transportin recycling. Surprisingly, translocation of transportin-substrate complexes into the nucleus requires neither Ran nor nucleoside triphosphates (NTPs). It is only nuclear RanGTP, not GTP hydrolysis, that is needed for dissociation of transportin-substrate complexes and for re-export of transportin to the cytoplasm. GTP hydrolysis is apparently required only to restore the import competence of the re-exported transportin and, thus, for multiple rounds of transportin-dependent import. In addition, we provide evidence that at least one type of substrate can also complete NPC passage mediated by importin beta independently of Ran and energy.