Localized corrosion of high performance metal alloys in an acid/salt environment

Various vacuum jacketed cryogenic supply lines at the Space Shuttle launch site at Kennedy Space Center use convoluted flexible expansion joints. The atmosphere at the launch site has a very high salt content, and during a launch, fuel combustion products include hydrochloric acid. This extremely corrosive environment has caused pitting corrosion failure in the thin walled 304L stainless steel flex hoses. A search was done to find a more corrosion resistant replacement material. The study focussed on 19 metal alloys. Tests which were performed include electrochemical corrosion testing, accelerated corrosion testing in a salt fog chamber, and long term exposure at a beach corrosion testing site. Based on the results of these tests, several nickel based alloys were found to have very high resistance to this corrosive environment. Also, there was excellent agreement between the electrochemical tests and the actual beach exposure tests. This suggests that electrochemical testing may be useful for narrowing the field of potential candidate alloys before subjecting samples to long term beach exposure

Singularities of Scattering Amplitudes on Unphysical Sheets and Their Interpretation

The analytic structure of two-particle scattering amplitudes on the unphysical sheet of the Riemann surface reached by crossing the two-particle cut is discussed. The singularities of the amplitudes there are shown to be poles and their physical interpretation is studied. The way in which bound states appear on the physical sheet in the Mandelstam representation, both as isolated poles and as cuts, is traced in detail. The properties of partial wave amplitudes and of the full amplitude as a function of energy and angle and of energy and momentum transfer are discussed. Finally, a few remarks are made in connection with unstable states

Equation of state and critical behavior of polymer models: A quantitative comparison between Wertheim's thermodynamic perturbation theory and computer simulations

We present an application of Wertheim's Thermodynamic Perturbation Theory (TPT1) to a simple coarse grained model made of flexibly bonded Lennard-Jones monomers. We use both the Reference Hyper-Netted-Chain (RHNC) and Mean Spherical approximation (MSA) integral equation theories to describe the properties of the reference fluid. The equation of state, the density dependence of the excess chemical potential, and the critical points of the liquid--vapor transition are compared with simulation results and good agreement is found. The RHNC version is somewhat more accurate, while the MSA version has the advantage of being almost analytic. We analyze the scaling behavior of the critical point of chain fluids according to TPT1 and find it to reproduce the mean field exponents: The critical monomer density is predicted to vanish as $n^{-1/2}$ upon increasing the chain length $n$ while the critical temperature is predicted to reach an asymptotic finite temperature that is attained as $n^{-1/2}$. The predicted asymptotic finite critical temperature obtained from the RHNC and MSA versions of TPT1 is found to be in good agreement with the $\Theta$ point of our polymer model as obtained from the temperature dependence of the single chain conformations.Comment: to appear in J.Chem.Phy

Electrochemical Evaluation of Stainless Steels in Acidified Sodium Chloride Solutions

This paper presents the results of an investigation in which several 300-series stainless steels (SS): AISI S30403 SS (UNS S30403), AISI 316L SS (UNS S31603), and AISI 317L SS (LINS S31703), as well as highly-alloyed: SS 254-SMO (UNS S32154), AL-6XN (N08367) and AL29-4C (UNS S44735), were evaluated using DC electrochemical techniques in three different electrolyte solutions. The solutions consisted of neutral 3.55% NaCl, 3.55% NaCl in 0.1N HCl, and 3.55% NaCl in 1.0N HCl. These solutions were chosen to simulate environments that are less, similar, and more aggressive, respectively, than the conditions at the Space Shuttle launch pads. The electrochemical test results were compared to atmospheric exposure data and evaluated for their ability to predict the long-term corrosion performance of the subject alloys. The electrochemical measurements for the six alloys indicated that the higher-alloyed SS 254-SMO, AL29-4C, and AL-6XN exhibited significantly higher resistance to localized corrosion than the 300-series SS. There was a correlation between the corrosion performance of the alloys during a two-year atmospheric exposure and the corrosion rates calculated from electrochemical (polarization resistance) measurements

Riemann-Einstein Structure from Volume and Gauge Symmetry

It is shown how a metric structure can be induced in a simple way starting with a gauge structure and a preferred volume, by spontaneous symmetry breaking. A polynomial action, including coupling to matter, is constructed for the symmetric phase. It is argued that assuming a preferred volume, in the context of a metric theory, induces only a limited modification of the theory.Comment: LaTeX, 13 pages; Added additional reference in Reference

Yang-Mills Interactions and Gravity in Terms of Clifford Algebra

A model of Yang-Mills interactions and gravity in terms of the Clifford algebra Cl(0,6) is presented. The gravity and Yang-Mills actions are formulated as different order terms in a generalized action. The feebleness of gravity as well as the smallness of the cosmological constant and theta terms are discussed at the classical level. The invariance groups, including the de Sitter and the Pati-Salam SU(4) subgroups, consist of gauge transformations from either side of an algebraic spinor. Upon symmetry breaking via the Higgs fields, the remaining symmetries are the Lorentz SO(1,3), color SU(3), electromagnetic U(1)_EM, and an additional U(1). The first generation leptons and quarks are identified with even and odd parts of spinor idempotent projections. There are still several shortcomings with the current model. Further research is needed to fully recover the standard model results.Comment: 20 pages, to appear in Advances in Applied Clifford Algebra

Reflection on multilayer mirrors beam profile and coherence properties

The main advantage of Bragg reflection from a multilayer mirror as a monochromator for hard X rays, is the higher photon flux density because of the larger spectral bandpass compared with crystal lattice reflection. The main disadvantage lies in the strong modulations of the reflected beam profile. This is a major issue for micro imaging applications, where multilayer based monochromators are frequently employed to deliver high photon flux density. A subject of particular interest is the origin of the beam profile modifications, namely the irregular stripe patterns, induced by the reflection on a multilayer. For multilayer coatings in general it is known that the substrate and its surface quality significantly influence the performance of mirrors, as the coating reproduces to a certain degree the roughness and shape of the substrate. This proceedings article reviews recent experiments that indicate potential options for producing wave front preserving multilayer mirrors, as well as new details on the particular mirrors our group has extensively studied in the pas

Snyder's Quantized Space-time and De Sitter Special Relativity

There is a one-to-one correspondence between Snyder's model in de Sitter space of momenta and the \dS-invariant special relativity. This indicates that physics at the Planck length $\ell_P$ and the scale $R=3/\Lambda$ should be dual to each other and there is in-between gravity of local \dS-invariance characterized by a dimensionless coupling constant $g=\ell_P/R\sim 10^{-61}$.Comment: 8 page

When Courts Collide: Integrated Domestic Violence Courts and Court Pluralism

This Article proposes court pluralism as a new theory for analyzing the role of the justice system in addressing domestic violence. It argues that a systemic view of the justice system is essential to developing coherent reform strategies, and lays out the foundation for taking into account the unique functions of civil and criminal justice in domestic violence cases. In doing so, the Article challenges the one-dimensional characterization of a fragmented court system as bad for victims of domestic violence that dominates legal scholarship, and shows that court fragmentation can be an opportunity and potential source of protection from systemic problems in the justice system. This more complete understanding of the significance of fragmentation in the justice system is especially important given current efforts to merge essential civil and criminal court functions within single, integrated domestic violence courts. The Article explores claims for integrated courts and argues that the value of court pluralism is overlooked. Part I introduces the problem of integrated courts in a pluralistic court system. Part II examines the normative function of criminal courts in relation to domestic violence cases and contrasts the remedies available to victims in criminal and civil courts. Part III critiques the rationale for integrated domestic violence courts from the standpoint of litigation strategy, and identifies alternative avenues for system reform. This Part also examines the ways in which integrated courts compromise the autonomy-enhancing functions of civil courts. Part IV shows that despite the advantages of civil courts for victims, the characterization of civil justice as relatively unproblematic is inaccurate, and revisits the normative role of the criminal courts. This Part demonstrates that the functionality of criminal courts is compromised by persistent process failures in dealing with domestic violence, and shows both the synergy between defendants’ rights and victims’ needs, and the inadequacy of evaluating domestic violence policies without taking court pluralism into account. This Part argues that, given the risks and lack of benefits to victims of integrating criminal and civil court functions, this reform strategy should be reconsidered in light of its impact on court pluralism. Part V, the conclusion, urges reformers to work to identify and improve the distinct functionalities of civil and criminal courts for victims of domestic violence while maintaining the benefits of court pluralism, and identifies priorities for future research