Effects of Dissimilar Metal Coupling, Potential Distribution, and Temper Condition on Galvanic Corrosion of 5086 Aluminum Alloy in Synthetic Seawater

The galvanic corrosion behavior of 5086 aluminum alloy in three tempers {Hll6, Hll7, H32) when coupled with more noble metals {1040 steel, naval brass, and Ti-150A titanium) and immersed in aerated synthetic seawater, was studied. Galvanic current density measurements, potentiodynamic polarization determinations, and optical and electron microscopic observations were made. Galvanic corrosion of 5086 aluminum was found to be independent of temper and to decrease in the order (of coupled metals) Ti > naval brass> 1040 steel. The effect of dissimilar metal coupling decreases with time due to the formation of corrosion or product deposits on both anodic and cathodic surfaces. Coverage of the surface of the aluminum (anodic) member of couples with corrosion products tends to promote the operation of local corrosion modes. Correlations have been made between corrosion product distribution and the distribution of dissolution attack by microscopic means, and the relation of these features to potential distribution is discussed.Naval Research, Metallurgy Program Office, Code 471N00014-77-WR-70215, NR-036-120Approved for public release; distribution is unlimited

The Effect of Flow Structure on Corrosion: Circling-Foil Studies on 90/10 Copper-Nickel, and Hydrodynamic Modeling of the Erosion-Corrosion Process

The effects of turbulent flow on the corrosion behavior of 90/10 Cu-Ni were studied experimentally in synthetic seawater electrolyte, using a circling foil apparatus at relative velocities up to about 6 m/sec. The flow field at the specimen surface was characterized by anemometric methods. Corrosion rates were determined by direct weight loss and by several electrochemical methods, including the linear polarization method and from Tafel plots; also zero resistance ammeter measurements were made on galvanic couples. Consideration was given to the question of the appropriate analytical approach to velocity (fluid flow) effects on corrosion processes. The contribution of convective diffusion is considered dominant over the velocity range studied, and the rate of eddy diffusivity (fine flow structure effects on mass transport) is described. The separate electrochemical and mechanical influences of high-intensity turbulent flows are considered.Office of Naval Research Metallurgy Program Office, Code 471N00014-78-WR-80105, NR-036-120Approved for public release; distribution is unlimited

Nonequilibrium wetting

When a nonequilibrium growing interface in the presence of a wall is considered a nonequilibrium wetting transition may take place. This transition can be studied trough Langevin equations or discrete growth models. In the first case, the Kardar-Parisi-Zhang equation, which defines a very robust universality class for nonequilibrium moving interfaces, with a soft-wall potential is considered. While in the second, microscopic models, in the corresponding universality class, with evaporation and deposition of particles in the presence of hard-wall are studied. Equilibrium wetting is related to a particular case of the problem, it corresponds to the Edwards-Wilkinson equation with a potential in the continuum approach or to the fulfillment of detailed balance in the microscopic models. In this review we present the analytical and numerical methods used to investigate the problem and the very rich behavior that is observed with them.Comment: Review, 36 pages, 16 figure

Mass‐loading the Earth's dayside magnetopause boundary layer and its effect on magnetic reconnection

When the interplanetary magnetic field is northward for a period of time, O+ from the high‐latitude ionosphere escapes along reconnected magnetic field lines into the dayside magnetopause boundary layer. Dual‐lobe reconnection closes these field lines, which traps O+ and mass loads the boundary layer. This O+ is an additional source of magnetospheric plasma that interacts with magnetosheath plasma through magnetic reconnection. This mass loading and interaction is illustrated through analysis of a magnetopause crossing by the Magnetospheric Multiscale spacecraft. While in the O+‐rich boundary layer, the interplanetary magnetic field turns southward. As the Magnetospheric Multiscale spacecraft cross the high‐shear magnetopause, reconnection signatures are observed. While the reconnection rate is likely reduced by the mass loading, reconnection is not suppressed at the magnetopause. The high‐latitude dayside ionosphere is therefore a source of magnetospheric ions that contributes often to transient reduction in the reconnection rate at the dayside magnetopause.publishedVersio

Application of non-HDL cholesterol for population-based cardiovascular risk stratification: results from the Multinational Cardiovascular Risk Consortium.

BACKGROUND: The relevance of blood lipid concentrations to long-term incidence of cardiovascular disease and the relevance of lipid-lowering therapy for cardiovascular disease outcomes is unclear. We investigated the cardiovascular disease risk associated with the full spectrum of bloodstream non-HDL cholesterol concentrations. We also created an easy-to-use tool to estimate the long-term probabilities for a cardiovascular disease event associated with non-HDL cholesterol and modelled its risk reduction by lipid-lowering treatment. METHODS: In this risk-evaluation and risk-modelling study, we used Multinational Cardiovascular Risk Consortium data from 19 countries across Europe, Australia, and North America. Individuals without prevalent cardiovascular disease at baseline and with robust available data on cardiovascular disease outcomes were included. The primary composite endpoint of atherosclerotic cardiovascular disease was defined as the occurrence of the coronary heart disease event or ischaemic stroke. Sex-specific multivariable analyses were computed using non-HDL cholesterol categories according to the European guideline thresholds, adjusted for age, sex, cohort, and classical modifiable cardiovascular risk factors. In a derivation and validation design, we created a tool to estimate the probabilities of a cardiovascular disease event by the age of 75 years, dependent on age, sex, and risk factors, and the associated modelled risk reduction, assuming a 50% reduction of non-HDL cholesterol. FINDINGS: Of the 524 444 individuals in the 44 cohorts in the Consortium database, we identified 398 846 individuals belonging to 38 cohorts (184 055 [48·7%] women; median age 51·0 years [IQR 40·7-59·7]). 199 415 individuals were included in the derivation cohort (91 786 [48·4%] women) and 199 431 (92 269 [49·1%] women) in the validation cohort. During a maximum follow-up of 43·6 years (median 13·5 years, IQR 7·0-20·1), 54 542 cardiovascular endpoints occurred. Incidence curve analyses showed progressively higher 30-year cardiovascular disease event-rates for increasing non-HDL cholesterol categories (from 7·7% for non-HDL cholesterol <2·6 mmol/L to 33·7% for ≥5·7 mmol/L in women and from 12·8% to 43·6% in men; p<0·0001). Multivariable adjusted Cox models with non-HDL cholesterol lower than 2·6 mmol/L as reference showed an increase in the association between non-HDL cholesterol concentration and cardiovascular disease for both sexes (from hazard ratio 1·1, 95% CI 1·0-1·3 for non-HDL cholesterol 2·6 to <3·7 mmol/L to 1·9, 1·6-2·2 for ≥5·7 mmol/L in women and from 1·1, 1·0-1·3 to 2·3, 2·0-2·5 in men). The derived tool allowed the estimation of cardiovascular disease event probabilities specific for non-HDL cholesterol with high comparability between the derivation and validation cohorts as reflected by smooth calibration curves analyses and a root mean square error lower than 1% for the estimated probabilities of cardiovascular disease. A 50% reduction of non-HDL cholesterol concentrations was associated with reduced risk of a cardiovascular disease event by the age of 75 years, and this risk reduction was greater the earlier cholesterol concentrations were reduced. INTERPRETATION: Non-HDL cholesterol concentrations in blood are strongly associated with long-term risk of atherosclerotic cardiovascular disease. We provide a simple tool for individual long-term risk assessment and the potential benefit of early lipid-lowering intervention. These data could be useful for physician-patient communication about primary prevention strategies. FUNDING: EU Framework Programme, UK Medical Research Council, and German Centre for Cardiovascular Research

A measurement of the tau mass and the first CPT test with tau leptons

We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(syst.) MeV using tau pairs from Z0 decays. To test CPT invariance we compare the masses of the positively and negatively charged tau leptons. The relative mass difference is found to be smaller than 3.0 10^-3 at the 90% confidence level.Comment: 10 pages, 4 figures, Submitted to Phys. Letts.

Measurement of the B0 Lifetime and Oscillation Frequency using B0->D*+l-v decays

The lifetime and oscillation frequency of the B0 meson has been measured using B0->D*+l-v decays recorded on the Z0 peak with the OPAL detector at LEP. The D*+ -> D0pi+ decays were reconstructed using an inclusive technique and the production flavour of the B0 mesons was determined using a combination of tags from the rest of the event. The results t_B0 = 1.541 +- 0.028 +- 0.023 ps, Dm_d = 0.497 +- 0.024 +- 0.025 ps-1 were obtained, where in each case the first error is statistical and the second systematic.Comment: 17 pages, 4 figures, submitted to Phys. Lett.

PAMELA/ATIC anomaly from the meta-stable extra dark matter component and the leptophilic Yukawa interaction

We present a supersymmetric model with two dark matter (DM) components explaining the galactic positron excess observed by PAMELA/HEAT and ATIC/PPB-BETS: One is the conventional (bino-like) lightest supersymmetric particle (LSP) \chi, and the other is a TeV scale meta-stable neutral singlet N_D, which is a Dirac fermion (N,N^c). In this model, N_D decays dominantly into \chi e^+e^- through an R parity preserving dimension 6 operator with the life time \tau_N\sim 10^{26} sec. We introduce a pair of vector-like superheavy SU(2) lepton doublets (L,L^c) and lepton singlets (E,E^c). The dimension 6 operator leading to the N_D decay is generated from the leptophilic Yukawa interactions by W\supset Ne^cE+Lh_dE^c+m_{3/2}l_1L^c with the dimensionless couplings of order unity, and the gauge interaction by {\cal L}\supset \sqrt{2} g'\tilde{e}^{c*}e^c\chi + h.c. The superheavy masses of the vector-like leptons (M_L, M_E\sim 10^{16} GeV) are responsible for the longevity of N_D. The low energy field spectrum in this model is just the MSSM fields and N_D. Even for the case that the portion of N_D is much smaller than that of \chi in the total DM density [{\cal O}(10^{-10}) \lesssim n_{N_D}/n_\chi], the observed positron excess can be explained by adopting relatively lighter masses of the vector-like leptons (10^{13} GeV \lesssim M_{L,E} \lesssim 10^{16} GeV). The smallness of the electron mass is also explained. This model is easily embedded in the flipped SU(5) grand unification, which is a leptophilic unified theory.Comment: 12 pages, published versio

Search for Higgs Bosons in e+e- Collisions at 183 GeV

The data collected by the OPAL experiment at sqrts=183 GeV were used to search for Higgs bosons which are predicted by the Standard Model and various extensions, such as general models with two Higgs field doublets and the Minimal Supersymmetric Standard Model (MSSM). The data correspond to an integrated luminosity of approximately 54pb-1. None of the searches for neutral and charged Higgs bosons have revealed an excess of events beyond the expected background. This negative outcome, in combination with similar results from searches at lower energies, leads to new limits for the Higgs boson masses and other model parameters. In particular, the 95% confidence level lower limit for the mass of the Standard Model Higgs boson is 88.3 GeV. Charged Higgs bosons can be excluded for masses up to 59.5 GeV. In the MSSM, mh > 70.5 GeV and mA > 72.0 GeV are obtained for tan{beta}>1, no and maximal scalar top mixing and soft SUSY-breaking masses of 1 TeV. The range 0.8 < tanb < 1.9 is excluded for minimal scalar top mixing and m{top} < 175 GeV. More general scans of the MSSM parameter space are also considered.Comment: 49 pages. LaTeX, including 33 eps figures, submitted to European Physical Journal

A Measurement of the Product Branching Ratio f(b->Lambda_b).BR(Lambda_b->Lambda X) in Z0 Decays

The product branching ratio, f(b->Lambda_b).BR(Lambda_b->Lambda X), where Lambda_b denotes any weakly-decaying b-baryon, has been measured using the OPAL detector at LEP. Lambda_b are selected by the presence of energetic Lambda particles in bottom events tagged by the presence of displaced secondary vertices. A fit to the momenta of the Lambda particles separates signal from B meson and fragmentation backgrounds. The measured product branching ratio is f(b->Lambda_b).BR(Lambda_b->Lambda X) = (2.67+-0.38(stat)+0.67-0.60(sys))% Combined with a previous OPAL measurement, one obtains f(b->Lambda_b).BR(Lambda_b->Lambda X) = (3.50+-0.32(stat)+-0.35(sys))%.Comment: 16 pages, LaTeX, 3 eps figs included, submitted to the European Physical Journal