COMPUTATIONAL MODELING OF CATHODIC LIMITATIONS ON LOCALIZED CORROSION OF WETTED SS 316L, AT ROOM TEMPERATURE

The ability of a SS316L surface wetted with a thin electrolyte layer to serve as an effective cathode for an active localized corrosion site was studied computationally. The dependence of the total net cathodic current, I{sub net}, supplied at the repassivation potential E{sub rp} (of the anodic crevice) on relevant physical parameters including water layer thickness (WL), chloride concentration ([Cl{sup -}]) and length of cathode (Lc) were investigated using a three-level, full factorial design. The effects of kinetic parameters including the exchange current density (i{sub o,c}) and Tafel slope ({beta}{sub c}) of oxygen reduction, the anodic passive current density (i{sub p}) (on the cathodic surface), and E{sub rp} were studied as well using three-level full factorial designs of [Cl{sup -}] and Lc with a fixed WL of 25 {micro}m. The study found that all the three parameters WL, [Cl{sup -}] and Lc as well as the interactions of Lc x WL and Lc x [Cl{sup -}] had significant impact on I{sub net}. A five-factor regression equation was obtained which fits the computation results reasonably well, but demonstrated that interactions are more complicated than can be explained with a simple linear model. Significant effects on I{sub net} were found upon varying either i{sub o,c}, {beta}{sub c}, or E{sub rp}, whereas i{sub p} in the studied range was found to have little impact. It was observed that I{sub net} asymptotically approached maximum values (I{sub max}) when Lc increased to critical minimum values. I{sub max} can be used to determine the stability of coupled localized corrosion and the critical Lc provides important information for experimental design and corrosion protection

Improved lower bounds for the ground-state energy of many-body systems

New lower bounds for the binding energy of a quantum-mechanical system of interacting particles are presented. The new bounds are expressed in terms of two-particle quantities and improve the conventional bounds of the Hall-Post type. They are constructed by considering not only the energy in the two-particle system, but also the structure of the pair wave function. We apply the formal results to various numerical examples, and show that in some cases dramatic improvement over the existing bounds is reached.Comment: 29 pages, 5 figures, to be published in Phys. Rev.

Epidemiologic Study of Dental Caries Experience and Between-Meal Eating Patterns

The relationship between dental caries and between-meal snacks was investigated in a study of 1,486 high school students. The participants completed a questionnaire on between-meal habits and then were given dental examinations. The lack of differences in dental caries between racial and geographic groups was not related to the frequency of sucrose-containing, between-meal snacks.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66591/2/10.1177_00220345730520022501.pd

Radiative corrections to low energy neutrino reactions

We show that the radiative corrections to charged current (CC) nuclear reactions with an electron(positron) in the final state are described by a universal function. The consistency of our treatment of the radiative corrections with the procedure used to extract the value of the axial coupling constant $g_A$ is discussed. To illustrate we apply our results to (anti)neutrino deuterium disintegration and to $pp$ fusion in the sun. The limit of vanishing electron mass is considered, and a simple formula valid for E_{obs}\gsim 1 MeV is obtained. The size of the nuclear structure-dependent effects is also discussed. Finally, we consider CC transitions with an electron(positron) in the initial state and discuss some applications to electron capture reactions.Comment: 23 pages, 5 figure

How model sets can be determined by their two-point and three-point correlations

We show that real model sets with real internal spaces are determined, up to translation and changes of density zero by their two- and three-point correlations. We also show that there exist pairs of real (even one dimensional) aperiodic model sets with internal spaces that are products of real spaces and finite cyclic groups whose two- and three-point correlations are identical but which are not related by either translation or inversion of their windows. All these examples are pure point diffractive. Placed in the context of ergodic uniformly discrete point processes, the result is that real point processes of model sets based on real internal windows are determined by their second and third moments.Comment: 19 page

Methane Mitigation:Methods to Reduce Emissions, on the Path to the Paris Agreement

The atmospheric methane burden is increasing rapidly, contrary to pathways compatible with the goals of the 2015 United Nations Framework Convention on Climate Change Paris Agreement. Urgent action is required to bring methane back to a pathway more in line with the Paris goals. Emission reduction from “tractable” (easier to mitigate) anthropogenic sources such as the fossil fuel industries and landfills is being much facilitated by technical advances in the past decade, which have radically improved our ability to locate, identify, quantify, and reduce emissions. Measures to reduce emissions from “intractable” (harder to mitigate) anthropogenic sources such as agriculture and biomass burning have received less attention and are also becoming more feasible, including removal from elevated-methane ambient air near to sources. The wider effort to use microbiological and dietary intervention to reduce emissions from cattle (and humans) is not addressed in detail in this essentially geophysical review. Though they cannot replace the need to reach “net-zero” emissions of CO2, significant reductions in the methane burden will ease the timescales needed to reach required CO2 reduction targets for any particular future temperature limit. There is no single magic bullet, but implementation of a wide array of mitigation and emission reduction strategies could substantially cut the global methane burden, at a cost that is relatively low compared to the parallel and necessary measures to reduce CO2, and thereby reduce the atmospheric methane burden back toward pathways consistent with the goals of the Paris Agreement

Non-Equilibrium Statistical Physics of Currents in Queuing Networks

We consider a stable open queuing network as a steady non-equilibrium system of interacting particles. The network is completely specified by its underlying graphical structure, type of interaction at each node, and the Markovian transition rates between nodes. For such systems, we ask the question ``What is the most likely way for large currents to accumulate over time in a network ?'', where time is large compared to the system correlation time scale. We identify two interesting regimes. In the first regime, in which the accumulation of currents over time exceeds the expected value by a small to moderate amount (moderate large deviation), we find that the large-deviation distribution of currents is universal (independent of the interaction details), and there is no long-time and averaged over time accumulation of particles (condensation) at any nodes. In the second regime, in which the accumulation of currents over time exceeds the expected value by a large amount (severe large deviation), we find that the large-deviation current distribution is sensitive to interaction details, and there is a long-time accumulation of particles (condensation) at some nodes. The transition between the two regimes can be described as a dynamical second order phase transition. We illustrate these ideas using the simple, yet non-trivial, example of a single node with feedback.Comment: 26 pages, 5 figure

Charge-Coupled Device Panoramic Radiography: Area Image Distortion Factors as Selected Image Layer Contours

Svrha: Svrha ove studije bila je odrediti svojstva čimbenika izobličenja kontura razlučivanja odabranog sloja slike ortopantomografa OP 100®Instrumentarium Imaging, Tuusula, Finland) kombiniranog sa senzorom vrste CCD (charge-coupled device) tipa (Trophy Radiologie, Vincennes, France). Materijal i metode: Upotrebom mreže kojom se određuje razlučivanje postavljene u razmacima uzduž iskustveno ustanovljenih putanja projekcijskog snopa, konture sloja slike proizvodene ortopantomografom OP 100® modificiranim s osjetilom DigiPan® prethodno su određene za granice razlučivanja od 4,0, 3,0 i 1,5 lp m m 1. Za određivanje čimbenika povećanja uz odabrane granice razlučivanja i vodoravne angulacije snopa bila je upotrebljena jedna šestokutna ispitna naprava, uz uporabu mjernog algoritma koji pripada vlastitom softwareu (programskoj podršci) osjetila DigiPan®. Zatim su upotrebljena vodoravna i okomita povećanja kako be se odredili čimbenici izobličenja za svaku konturu razlučivanja uzduž odabrane angulacije snopa. Rezultati: Uz konture razlučivanja sloja slike od 4 lp m m 1 svi čimbenici izobličenja površine bili su približno jedinica. U području omeđenom tim konturama razlučivanja mjerni je algoritam kompenzirao učinke izobličenja svojstvene povećanju, uzrokovanom geometrijom snopa X-zraka. Uz 1,5 lp m m 1 čimbenici izobličenja površine kretali su se od 1,16 do 1,19 facijalno i 1,14 do 1,22 lingvalno u odnosu prema konturi sloja slike najvećeg razlučivanja. Kontura sloja slike s najvećim prostornim razlučivanjem bila je postavljena lingvalno u odnosu spram geometrijskome središtu žarišta. Zaključak: Upotrebom osjetila DigiPan® i uređaja OP 100® ustanovljene vrijednosti izobličenja odgovaraju vrijednostima već ustanovljenim s pomoću konvencionalnih receptora vrste film/zaslon. U području najvećeg razlučivanja mjerni algoritam programa djelotvorno je kompenzirao izobličenje povećanja projekcionog snopa.Objectives: The aim of this study was to determine the distortion factor characteristics for selected image layer resolution contours of the Orthopantomograph OP 100® (Instrumentarium Imaging, Tuusula, Finland), combined with the DigiPan® (Trophy Radiologie, Vincennes, France) charge-coupled device receptor. Material and Methods: Using a resolution grid positioned at intervals along empirically determined beam projection paths, the image layer contours produced with the DigiPan® modification o f the Orthopantomograph OP 100® had previously been determined for resolution limits o f 4.0, 3.0 and 1.5 Ip m m 1. An hexagonal test device was used to determine the magnification factors at the selected resolution limits and horizontal beam angulations using the resident measurement algorithm o f the DigiPan® proprietary software. The horizontal and vertical magnifications were then used to determine the distortion factors at each resolution contour along selected beam angulations. Results: At the image layer resolution contours of 4 Ip m m 1 all area distortion factors approached unity. Furthermore, in the region bounded by these resolution contours the measurement algorithm compensated for the inherent magnification distortion artefact caused by the X-ray beam geometry. At 1.5 Ip m m 1, the area distortion factors ranged from 1.16 to 1.19 facially and 1.14 to 1.22 lingually to image layer contour of maximum resolution. The image layer contour of maximum spatial resolution was positioned lingually to the geometric center o f the focal trough. Conclusion: Using the DigiPan®, and the op 100® the distortion values conform o f those previously found using conventional film/screen receptors. In the region o f maximum resolution, the software measurement algotirhm effectively compensated for beam- projection magnification distortion

Summer CO2 evasion from streams and rivers in the Kolyma River basin, north-east Siberia

Inland water systems are generally supersaturated in carbon dioxide (CO2) and are increasingly recognized as playing an important role in the global carbon cycle. The Arctic may be particularly important in this respect, given the abundance of inland waters and carbon contained in Arctic soils; however, a lack of trace gas measurements from small streams in the Arctic currently limits this understanding.We investigated the spatial variability of CO2 evasion during the summer low-flow period from streams and rivers in the northern portion of the Kolyma River basin in north-eastern Siberia. To this end, partial pressure of carbon dioxide (pCO2) and gas exchange velocities (k) were measured at a diverse set of streams and rivers to calculate CO2 evasion fluxes. We combined these CO2 evasion estimates with satellite remote sensing and geographic information system techniques to calculate total areal CO2 emissions. Our results show that small streams are substantial sources of atmospheric CO2 owing to high pCO2 and k, despite being a small portion of total inland water surface area. In contrast, large rivers were generally near equilibrium with atmospheric CO2. Extrapolating our findings across the Panteleikha-Ambolikha sub-watersheds demonstrated that small streams play a major role in CO2 evasion, accounting for 86% of the total summer CO2 emissions from inland waters within these two sub-watersheds. Further expansion of these regional CO2 emission estimates across time and space will be critical to accurately quantify and understand the role of Arctic streams and rivers in the global carbon budget