Electrochemical Quartz Crystal Microbalance Study of Corrosion of Phases in AA2024

The electrochemical quartz crystal microbalance (EQCM) was used to directly measure the dissolution rate at cathodic potentials, and thus the cathodic corrosion rate, of thin-film analogs of phases in AA2024. Thin films of pure Al, Al-4% Cu, and Al2Cu were studied in 0.1 M NaCl containing 0, 10^-4, or 10^-2 M Cr2O7 . A range of cathodic potentials was studied for each material. The true cathodic current density was calculated from the difference of the net current density and the dissolution rate, which was determined by the EQCM. For pure Al and Al-4Cu, the cathodic corrosion rate was large relative to the net current density, so the true cathodic current density was considerably larger than the measured net current density. The cathodic current density was almost identical to the net current density for Al2Cu because the dissolution rate was very small compared to the cathodic reaction rate. Various potentials in the limiting oxygen reduction reaction region were examined, but the effect of the applied potential was small. The presence of dichromate in solution decreased both the cathodic corrosion rate and the cathodic current density on these thin-film analogs. In particular, it decreased more effectively the cathodic reaction rate on Al2Cu, which can support faster cathodic reaction rates.This work was supported by the United States Air Force Office of Scientific Research Grant no. F49620-96-1-0479 under the guidance of Dr. Paul Trulove

Easy come-easy go divisible cash

Recently, there has been an interest in making electronic cash protocols more practical for electronic commerce by developing e-cash which is divisible (e.g., a coin which can be spent incrementally but total purchases are limited to the monetary value of the coin). In Crypto`95, T. Okamoto presented the first practical divisible, untraceable, off-line e-cash scheme, which requires only O(log N) computations for each of the withdrawal, payment and deposit procedures, where N = (total coin value)/(smallest divisible unit). However, Okamoto`s set-up procedure is quite inefficient (on the order of 4,000 multi-exponentiations and depending on the size of the RSA modulus). The authors formalize the notion of range-bounded commitment, originally used in Okamoto`s account establishment protocol, and present a very efficient instantiation which allows one to construct the first truly efficient divisible e-cash system. The scheme only requires the equivalent of one (1) exponentiation for set-up, less than 2 exponentiations for withdrawal and around 20 for payment, while the size of the coin remains about 300 Bytes. Hence, the withdrawal protocol is 3 orders of magnitude faster than Okamoto`s, while the rest of the system remains equally efficient, allowing for implementation in smart-cards. Similar to Okamoto`s, the scheme is based on proofs whose cryptographic security assumptions are theoretically clarified

Visualising apoptosis in live zebrafish using fluorescence lifetime imaging with optical projection tomography to map FRET biosensor activity in space and time

Fluorescence lifetime imaging (FLIM) combined with optical projection tomography (OPT) has the potential to map Förster resonant energy transfer (FRET) readouts in space and time in intact transparent or near transparent live organisms such as zebrafish larvae, thereby providing a means to visualise cell signalling processes in their physiological context. Here the first application of FLIM OPT to read out biological function in live transgenic zebrafish larvae using a genetically expressed FRET biosensor is reported. Apoptosis, or programmed cell death, is mapped in 3-D by imaging the activity of a FRET biosensor that is cleaved by Caspase 3, which is a key effector of apoptosis. Although apoptosis is a naturally occurring process during development, it can also be triggered in a variety of ways, including through gamma irradiation. FLIM OPT is shown here to enable apoptosis to be monitored over time, in live zebrafish larvae via changes in Caspase 3 activation following gamma irradiation at 24 hours post fertilisation. Significant apoptosis was observed at 3.5 hours post irradiation, predominantly in the head region

Effects of Sodium Chloride Particles, Ozone, UV, and Relative Humidity on Atmospheric Corrosion of Silver

The corrosion of Ag contaminated with NaCl particles in gaseous environments containing humidity and ozone was investigated. In particular, the effects of relative humidity and UV light illumination were quantitatively analyzed using a coulometric reduction technique. The atmospheric corrosion of Ag was greatly accelerated in the presence of ozone and UV light. Unlike bare Ag (i.e., with no NaCl particles on the surface), Ag with NaCl exhibited fast corrosion even in the dark, with no UV in the presence of ozone. Samples exposed to different outdoor environments and samples exposed in a salt spray chamber were studied for comparison. Ag corroded at extremely low rates in a salt spray chamber partly because of the combined absence of light and oxidizing agents such as ozone

MiFID II Unbundling and Sell Side Analyst Research

We examine the effect of MiFID II, which mandated the unbundling and separate pricing of analyst research in Europe beginning in 2018. We find that the requirements of MiFID II were associated with a reduction in analyst following for European firms relative to US firms, with decreases in coverage greatest for firms that were larger, older and less volatile, and had greater coverage and more accurate consensus forecasts. Remaining analysts follow fewer firms and issue fewer forecasts, consistent with increased focus, and appear to increase their efforts on the firms they continue to cover. In particular, forecasts become more accurate, are more likely to be disaggregated and include recommendations, and are accompanied by larger stock price reactions. Consistent with increased effort to curry favor with management, analysts issue more optimistic recommendations and beatable earnings forecasts. While individual forecasts are more informative, the overall information environment for the average firm tends to deteriorate, with less aggregate information conveyed by analyst forecasts, a greater proportion of information delayed to earnings announcements and higher average bid-ask spreads. Taken as a whole, results are consistent with a reduction in analyst following mitigated by an increase in focus and effort by remaining analysts, but with an overall negative effect on the information environment

Geometric Parameterization of J/ΨJ/\Psi Absorption in Heavy Ion Collisions

We calculate the survival probability of $J/\Psi$ particles in various colliding systems using a Glauber model. An analysis of recent data has reported a $J/\Psi$-nucleon breakup cross section of 6.2$\pm$0.7 mb derived from an exponential fit to the ratio of $J/\Psi$ to Drell-Yan yields as a function of a simple, linearly-averaged mean path length through the nuclear medium. Our calculations indicate that, due to the nature of the calculation, this approach yields an apparent breakup cross section which is systematically lower than the actual value.Comment: LaTex, 7 pages, 2 figure

The T3SS effector EspT defines a new category of invasive enteropathogenic E. coli (EPEC) which form intracellular actin pedestals.

Enteropathogenic Escherichia coli (EPEC) strains are defined as extracellular pathogens which nucleate actin rich pedestal-like membrane extensions on intestinal enterocytes to which they intimately adhere. EPEC infection is mediated by type III secretion system effectors, which modulate host cell signaling. Recently we have shown that the WxxxE effector EspT activates Rac1 and Cdc42 leading to formation of membrane ruffles and lamellipodia. Here we report that EspT-induced membrane ruffles facilitate EPEC invasion into non-phagocytic cells in a process involving Rac1 and Wave2. Internalized EPEC resides within a vacuole and Tir is localized to the vacuolar membrane, resulting in actin polymerization and formation of intracellular pedestals. To the best of our knowledge this is the first time a pathogen has been shown to induce formation of actin comets across a vacuole membrane. Moreover, our data breaks the dogma of EPEC as an extracellular pathogen and defines a new category of invasive EPEC

Modeling seismic wave propagation and amplification in 1D/2D/3D linear and nonlinear unbounded media

To analyze seismic wave propagation in geological structures, it is possible to consider various numerical approaches: the finite difference method, the spectral element method, the boundary element method, the finite element method, the finite volume method, etc. All these methods have various advantages and drawbacks. The amplification of seismic waves in surface soil layers is mainly due to the velocity contrast between these layers and, possibly, to topographic effects around crests and hills. The influence of the geometry of alluvial basins on the amplification process is also know to be large. Nevertheless, strong heterogeneities and complex geometries are not easy to take into account with all numerical methods. 2D/3D models are needed in many situations and the efficiency/accuracy of the numerical methods in such cases is in question. Furthermore, the radiation conditions at infinity are not easy to handle with finite differences or finite/spectral elements whereas it is explicitely accounted in the Boundary Element Method. Various absorbing layer methods (e.g. F-PML, M-PML) were recently proposed to attenuate the spurious wave reflections especially in some difficult cases such as shallow numerical models or grazing incidences. Finally, strong earthquakes involve nonlinear effects in surficial soil layers. To model strong ground motion, it is thus necessary to consider the nonlinear dynamic behaviour of soils and simultaneously investigate seismic wave propagation in complex 2D/3D geological structures! Recent advances in numerical formulations and constitutive models in such complex situations are presented and discussed in this paper. A crucial issue is the availability of the field/laboratory data to feed and validate such models.Comment: of International Journal Geomechanics (2010) 1-1

Bcar1/p130Cas is essential for ventricular development and neural crest cell remodelling of the cardiac outflow tract.

AIM: The adapter protein p130Cas, encoded by the Bcar1 gene, is a key regulator of cell movement, adhesion, and cell cycle control in diverse cell types. Bcar1 constitutive knockout mice are embryonic lethal by embryonic days (E) 11.5-12.5, but the role of Bcar1 in embryonic development remains unclear. Here, we investigated the role of Bcar1 specifically in cardiovascular development and defined the cellular and molecular mechanisms disrupted following targeted Bcar1 deletions. METHODS AND RESULTS: We crossed Bcar1 floxed mice with Cre transgenic lines allowing for cell-specific knockout either in smooth muscle and early cardiac tissues (SM22-Cre), mature smooth muscle cells (smMHC-Cre), endothelial cells (Tie2-Cre), second heart field cells (Mef2c-Cre), or neural crest cells (NCC) (Pax3-Cre) and characterised these conditional knock outs using a combination of histological and molecular biology techniques.Conditional knockout of Bcar1 in SM22-expressing smooth muscle cells and cardiac tissues (Bcar1SM22KO) was embryonically lethal from E14.5-15.5 due to severe cardiovascular defects, including abnormal ventricular development and failure of outflow tract (OFT) septation leading to a single outflow vessel reminiscent of persistent truncus arteriosus. SM22-restricted loss of Bcar1 was associated with failure of OFT cushion cells to undergo differentiation to septal mesenchymal cells positive for SMC-specific α-actin, and disrupted expression of proteins and transcription factors involved in epithelial-to-mesenchymal transformation (EMT). Furthermore, knockout of Bcar1 specifically in NCC (Bcar1PAX3KO) recapitulated part of the OFT septation and aortic sac defects seen in the Bcar1SM22KO mutants, indicating a cell-specific requirement for Bcar1 in NCC essential for OFT septation. In contrast, conditional knockouts of Bcar1 in differentiated smooth muscle, endothelial cells, and second heart field cells survived to term and were phenotypically normal at birth and post-natally. CONCLUSIONS: Our work reveals a cell-specific requirement for Bcar1 in NCC, early myogenic and cardiac cells, essential for OFT septation, myocardialisation and EMT/cell cycle regulation and differentiation to myogenic lineages. TRANSLATIONAL PERSPECTIVE: The molecular pathways coordinating cardiogenesis and the remodelling of the OFT are complex, and dysregulation of these pathways causes human heart defects. Our findings highlight a specific requirement for Bcar1 essential for cardiogenesis. Furthermore, the failure of OFT septation in Bcar1SM22KO mice resembles persistent truncus arteriosus (PTA), a feature of several human congenital heart diseases, including DiGeorge Syndrome. Our findings have implications for the mechanisms underlying the pathogenesis of congenital heart disease, and suggest that mice with conditional Bcar1 deletions may be useful models for dissecting mechanisms involved in the pathogenesis of human heart defects

Unraveling the ecological processes modulating the population structure of Escherichia coli in a highly polluted urban stream network

Escherichia coli dynamics in urban watersheds are affected by a complex balance among external inputs, niche modulation and genetic variability. To explore the ecological processes influencing E. coli spatial patterns, we analyzed its abundance and phylogenetic structure in water samples from a stream network with heterogeneous urban infrastructure and environmental conditions. Our results showed that environmental and infrastructure variables, such as macrophyte coverage, DIN and sewerage density, mostly explained E. coli abundance. Moreover, main generalist phylogroups A and B1 were found in high proportion, which, together with an observed negative relationship between E. coli abundance and phylogroup diversity, suggests that their dominance might be due to competitive exclusion. Lower frequency phylogroups were associated with sites of higher ecological disturbance, mainly involving simplified habitats, higher drainage infrastructure and septic tank density. In addition to the strong negative relationship between phylogroup diversity and dominance, the occurrence of these phylogroups would be associated with increased facilitated dispersal. Nutrients also contributed to explaining phylogroup distribution. Our study proposes the differential contribution of distinct ecological processes to the patterns of E. coli in an urban watershed, which is useful for the monitoring and management of fecal pollution.Fil: Saraceno, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Gómez Lugo, Sebastian. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Ortiz, Nicolás. Provincia de Mendoza. Ministerio de Infraestructura y Vivienda. Secretaria de Obras Publicas. Instituto Nacional del Agua; ArgentinaFil: Gómez, Bárbara M.. Provincia de Mendoza. Ministerio de Infraestructura y Vivienda. Secretaria de Obras Publicas. Instituto Nacional del Agua; ArgentinaFil: Sabio y García, Carmen Alejandra. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Frankel, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Graziano, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin