The Anodic Dissolution Of Cadmium

The anodic dissolution of cadmium has been studied in aqueous solutions containing Cl−, Br−, I−, Ac−, SO4=, and NO3− ions. The normal valence (+2) was found in all solutions with the exception of NO3−. The apparent valence (calculated) of cadmium ions in nitrate solutions varied from 1.2 to 2.0 and was found to be a function of NO3− concentration, current density, and temperature. An anodic dissolution mechanism has been proposed involving local corrosion and disintegration of the anode which is consistent with the experimental results. © 1967, The Electrochemical Society, Inc. All rights reserved

UBC 97 and ACI 318-02 Code Comparison - Summary Report

Introduction Recognizing there have been questions on the differences between the alternate slender wall design procedures in 1997 UBC and in ACI 318-02, the SEAOSC Board authorized a Task Group to provide a comprehensive review of the two design procedures. The ACI procedure was adopted by IBC 2000 and subsequent code editions. As quoted in ACI 318R-02 Commentary Section R14.8, Section 14.8 is based on the corresponding requirements in the UBC and experimental research of the Test Report by SCCACI-SEAOSC. This summary report includes review of source documents, code comparison, and background of the design provisions under UBC and under ACI, respectively. A comprehensive review of the 1980 test data was made in addition to analytical comparison of sample wall panel design under each of the two procedures. Pursuant to the comparative design and validation of the original data, a list of findings is presented in the Report. Other design considerations though not part of the code comparison are discussed in order to encourage further studies by other groups. The report concludes with recommendations to SEAOSC Board and proposed changes to ACI. Code Comparison Under 97 UBC Section 1914.8, the cracked moment is based on fr = 5 √ f ´c.; and in ACI 318-02 Section 14.8, the cracked moment is based on fr = 7.5 √ f ´c. This also means that the Mcr (UBC) = 2/3 Mcr (ACI) in the application of the two design procedures. In the 97 UBC, a linear interpolation between Δcr and Δn is permitted in obtaining Δs in order to simplify the slender wall panel design for Ms \u3e 5 √ f ´c Ig/yt. The ACI procedure employs effective moment of inertia and a magnified moment for the combined moment due to lateral and eccentric vertical load, also know as the P-Δ effect. Table 1 gives section by section comparison between the alternate slender wall design procedures. Review of 1980 Test Data This Task Group was able to review and re-analyze the original test data. Verification of the 1980 data using adjusted lateral force and deflection data was performed. The analytical result follows closely with the bilinear load deflection characteristic. Lateral deflection increases rapidly when the moment exceeds two-third (2/3) of Mcr (as defined by ACI). The calculated moments for each of the twelve test panel correlate closely with the empirical test data. The load deflection curves and plots for the low axial loads versus moment interaction curve further validate the UBC design procedure. ACI needs to improve its methodology in computing Mu and Ie so that computed results would follow a bilinear load deflection characteristic. Summary of Findings Summary of comparative design examples is given on Table 5. Design based on ACI procedure is normally controlled by strength with service load deflection less than Δcr. ACI procedure significantly under-estimates service load deflection in comparison to the UBC procedure with increase lateral force and/ or axial load. Where wall panel design based on ACI procedures meets strength and deflection limit, the corresponding wall panel calculation based on UBC procedure may exceed the deflection limit. Recommendations To calculate service load deflection, use E/1.4 for earthquake forces Recommend to appropriate enforcement agencies that adoption of the 2003 IBC provisions on alternate design of slender wall procedure should incorporate proposed changes to ACI 318-05 Section 14.8.4. Modification to ACI 318-05 Section 14.8.4 -delete equations (14-8) and (14-9) and the last paragraph in total, and replace with the following after the first paragraph: “Δs = 0.67Δ cr + (Ms –0.67Mcr )(Δn –0.67Δcr)÷ (Mn-0.67Mcr); for Ms \u3e 0.67Mcr (14-8) Δs = 5 Ms lc2 ÷ (48Ec Ig) ; for Ms\u3c.67Mcr (14-9) Send a letter to ACI-318 addressing the concerns in using the ACI alternate design of slender wall procedure and requesting ACI 318 to correct statements under Commentary R14.8

Post-Newtonian Models of Binary Neutron Stars

Using an energy variational method, we calculate quasi-equilibrium configurations of binary neutron stars modeled as compressible triaxial ellipsoids obeying a polytropic equation of state. Our energy functional includes terms both for the internal hydrodynamics of the stars and for the external orbital motion. We add the leading post-Newtonian (PN) corrections to the internal and gravitational energies of the stars, and adopt hybrid orbital terms which are fully relativistic in the test-mass limit and always accurate to PN order. The total energy functional is varied to find quasi-equilibrium sequences for both corotating and irrotational binaries in circular orbits. We examine how the orbital frequency at the innermost stable circular orbit depends on the polytropic index n and the compactness parameter GM/Rc^2. We find that, for a given GM/Rc^2, the innermost stable circular orbit along an irrotational sequence is about 17% larger than the innermost secularly stable circular orbit along the corotating sequence when n=0.5, and 20% larger when n=1. We also examine the dependence of the maximum neutron star mass on the orbital frequency and find that, if PN tidal effects can be neglected, the maximum equilibrium mass increases as the orbital separation decreases.Comment: 53 pages, LaTex, 9 figures as 10 postscript files, accepted by Phys. Rev. D, replaced version contains updated reference

Solution of the infinite range t-J model

The t-J model with constant t and J between any pair of sites is studied by exploiting the symmetry of the Hamiltonian with respect to site permutations. For a given number of electrons and a given total spin the exchange term simply yields an additive constant. Therefore the real problem is to diagonalize the "t- model", or equivalently the infinite U Hubbard Hamiltonian. Using extensively the properties of the permutation group, we are able to find explicitly both the energy eigenvalues and eigenstates, labeled according to spin quantum numbers and Young diagrams. As a corollary we also obtain the degenerate ground states of the finite $U$ Hubbard model with infinite range hopping -t>0.Comment: 15 pages, 2 figure

A Link to the Past: Using Markov Chain Monte Carlo Fitting to Constrain Fundamental Parameters of High-Redshift Galaxies

We have a developed a new method for fitting spectral energy distributions (SEDs) to identify and constrain the physical properties of high-redshift (4 < z < 8) galaxies. Our approach uses an implementation of Bayesian based Markov Chain Monte Carlo (PiMC^2) that allows us to compare observations to arbitrarily complex models and to compute 95% credible intervals that provide robust constraints for the model parameters. The work is presented in 2 sections. In the first, we test PiMC^2 using simulated SEDs to not only confirm the recovery of the known inputs but to assess the limitations of the method and identify potential hazards of SED fitting when applied specifically to high redshift (z>4) galaxies. Our tests reveal five critical results: 1) the ability to confidently constrain metallicity, population ages, and Av all require photometric accuracy better than what is currently achievable (i.e. less than a few percent); 2) the ability to confidently constrain stellar masses (within a factor of two) can be achieved without the need for high-precision photometry; 3) the addition of IRAC photometry does not guarantee that tighter constraints of the stellar masses and ages can be defined; 4) different assumptions about the star formation history can lead to significant biases in mass and age estimates; and 5) we are able to constrain stellar age and Av of objects that are both young and relatively dust free. In the second part of the paper we apply PiMC^2 to 17 4<z<8 objects, including the GRAPES Ly alpha sample (4<z<6), supplemented by HST/WFC3 near-IR observations, and several broad band selected z>6 galaxies. Using PiMC^2, we are able to constrain the stellar mass of these objects and in some cases their stellar age and find no evidence that any of these sources formed at a redshift much larger than z_f=8, a time when the Universe was ~ 0.6 Gyr old.Comment: Submitted to ApJ (Full abstract, 47 pages, 17 figures, 7 tables

A Link to the Past: Using Markov Chain Monte Carlo Fitting to Constrain Fundamental Parameters of High-Redshift Galaxies

We have a developed a new method for fitting spectral energy distributions (SEDs) to identify and constrain the physical properties of high-redshift (4 < z < 8) galaxies. Our approach uses an implementation of Bayesian based Markov Chain Monte Carlo (PiMC^2) that allows us to compare observations to arbitrarily complex models and to compute 95% credible intervals that provide robust constraints for the model parameters. The work is presented in 2 sections. In the first, we test PiMC^2 using simulated SEDs to not only confirm the recovery of the known inputs but to assess the limitations of the method and identify potential hazards of SED fitting when applied specifically to high redshift (z>4) galaxies. Our tests reveal five critical results: 1) the ability to confidently constrain metallicity, population ages, and Av all require photometric accuracy better than what is currently achievable (i.e. less than a few percent); 2) the ability to confidently constrain stellar masses (within a factor of two) can be achieved without the need for high-precision photometry; 3) the addition of IRAC photometry does not guarantee that tighter constraints of the stellar masses and ages can be defined; 4) different assumptions about the star formation history can lead to significant biases in mass and age estimates; and 5) we are able to constrain stellar age and Av of objects that are both young and relatively dust free. In the second part of the paper we apply PiMC^2 to 17 4<z<8 objects, including the GRAPES Ly alpha sample (4<z<6), supplemented by HST/WFC3 near-IR observations, and several broad band selected z>6 galaxies. Using PiMC^2, we are able to constrain the stellar mass of these objects and in some cases their stellar age and find no evidence that any of these sources formed at a redshift much larger than z_f=8, a time when the Universe was ~ 0.6 Gyr old.Comment: Submitted to ApJ (Full abstract, 47 pages, 17 figures, 7 tables

A comparison of collision cross section values obtained via travelling wave ion mobility-mass spectrometry and ultra high performance liquid chromatography-ion mobility-mass spectrometry : application to the characterisation of metabolites in rat urine

A comprehensive Collision Cross Section (CCS) library was obtained via Travelling Wave Ion Guide mobility measurements through direct infusion (DI). The library consists of CCS and Mass Spectral (MS) data in negative and positive ElectroSpray Ionisation (ESI) mode for 463 and 479 endogenous metabolites, respectively. For both ionisation modes combined, TWCCSN2 data were obtained for 542 non-redundant metabolites. These data were acquired on two different ion mobility enabled orthogonal acceleration QToF MS systems in two different laboratories, with the majority of the resulting TWCCSN2 values (from detected compounds) found to be within 1% of one another. Validation of these results against two independent, external TWCCSN2 data sources and predicted TWCCSN2 values indicated to be within 1-2% of these other values. The same metabolites were then analysed using a rapid reversed-phase ultra (high) performance liquid chromatographic (U(H)PLC) separation combined with IM and MS (IM-MS) thus providing retention time (tr), m/z and TWCCSN2 values (with the latter compared with the DI-IM-MS data). Analytes for which TWCCSN2 values were obtained by U(H)PLC-IM-MS showed good agreement with the results obtained from DI-IM-MS. The repeatability of the TWCCSN2 values obtained for these metabolites on the different ion mobility QToF systems, using either DI or LC, encouraged the further evaluation of the U(H)PLC-IM-MS approach via the analysis of samples of rat urine, from control and methotrexate-treated animals, in order to assess the potential of the approach for metabolite identification and profiling in metabolic phenotyping studies. Based on the database derived from the standards 63 metabolites were identified in rat urine, using positive ESI, based on the combination of tr, TWCCSN2 and MS data.</p

Continuous, Real-Time Monitoring of Cocaine in Undiluted Blood Serum via a Microfluidic, Electrochemical Aptamer-Based Sensor

The development of a biosensor system capable of continuous, real-time measurement of small-molecule analytes directly in complex, unprocessed aqueous samples has been a significant challenge, and successful implementation has been achieved for only a limited number of targets. Towards a general solution to this problem, we report here the Microfluidic Electrochemical Aptamer-based Sensor (MECAS) chip wherein we integrate target-specific DNA aptamers that fold, and thus generate an electrochemical signal, in response to the analyte with a microfluidic detection system. As a model, we demonstrate the continuous, real-time (~1 minute time resolution) detection of the small molecule drug cocaine at near physiological, low micromolar concentrations directly in undiluted, otherwise unmodified blood serum. We believe our approach of integrating folding-based electrochemical sensors with miniaturized detection systems may lay the ground work for the realtime, point-of-care detection of a wide variety of molecular targets

Gβγ subunits inhibit Epac-induced melanoma cell migration

<p>Abstract</p> <p>Background</p> <p>Recently we reported that activation of Epac1, an exchange protein activated by cAMP, increases melanoma cell migration via Ca ²⁺release from the endoplasmic reticulum (ER). G-protein βγ subunits (Gβγ) are known to act as an independent signaling molecule upon activation of G-protein coupled receptor. However, the role of Gβγ in cell migration and Ca ²⁺signaling in melanoma has not been well studied. Here we report that there is crosstalk of Ca ²⁺signaling between Gβγ and Epac in melanoma, which plays a role in regulation of cell migration.</p> <p>Methods</p> <p>SK-Mel-2 cells, a human metastatic melanoma cell line, were mainly used in this study. Intracellular Ca ²⁺was measured with Fluo-4AM fluorescent dyes. Cell migration was examined using the Boyden chambers.</p> <p>Results</p> <p>The effect of Gβγ on Epac-induced cell migration was first examined. Epac-induced cell migration was inhibited by mSIRK, a Gβγ -activating peptide, but not its inactive analog, L9A, in SK-Mel-2 cells. Guanosine 5', α-β-methylene triphosphate (Gp(CH2)pp), a constitutively active GTP analogue that activates Gβγ, also inhibited Epac-induced cell migration. In addition, co-overexpression of β1 and γ2, which is the major combination of Gβγ, inhibited Epac1-induced cell migration. By contrast, when the C-terminus of β adrenergic receptor kinase (βARK-CT), an endogenous inhibitor for Gβγ, was overexpressed, mSIRK's inhibitory effect on Epac-induced cell migration was negated, suggesting the specificity of mSIRK for Gβγ. We next examined the effect of mSIRK on Epac-induced Ca ²⁺response. When cells were pretreated with mSIRK, but not with L9A, 8-(4-Methoxyphenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8-pMeOPT), an Epac-specific agonist, failed to increase Ca ²⁺signal. Co-overexpression of β1 and γ2 subunits inhibited 8-pMeOPT-induced Ca ²⁺elevation. Inhibition of Gβγ with βARK-CT or guanosine 5'-O-(2-thiodiphosphate) (GDPβS), a GDP analogue that inactivates Gβγ, restored 8-pMeOPT-induced Ca ²⁺elevation even in the presence of mSIRK. These data suggested that Gβγ inhibits Epac-induced Ca ²⁺elevation. Subsequently, the mechanism by which Gβγ inhibits Epac-induced Ca ²⁺elevation was explored. mSIRK activates Ca ²⁺influx from the extracellular space. In addition, W-5, an inhibitor of calmodulin, abolished mSIRK's inhibitory effects on Epac-induced Ca ²⁺elevation, and cell migration. These data suggest that, the mSIRK-induced Ca ²⁺from the extracellular space inhibits the Epac-induced Ca ²⁺release from the ER, resulting suppression of cell migration.</p> <p>Conclusion</p> <p>We found the cross talk of Ca ²⁺signaling between Gβγ and Epac, which plays a major role in melanoma cell migration.</p