Isotopic Evidence for Sources of Dissolved Carbon and the Role of Organic Matter Respiration in the Fraser River Basin, Canada

Sources of dissolved and particulate carbon to the Fraser River system vary significantly in space and time. Tributaries in the northern interior of the basin consistently deliver higher concentrations of dissolved organic carbon (DOC) to the main stem than other tributaries. Based on samples collected near the Fraser River mouth throughout 2013, the radiocarbon age of DOC exported from the Fraser River does not change significantly across seasons despite a spike in DOC concentration during the freshet, suggesting modulation of heterogeneous upstream signals during transit through the river basin. Dissolved inorganic carbon (DIC) concentrations are highest in the Rocky Mountain headwater region where carbonate weathering is evident, but also in tributaries with high DOC concentrations, suggesting that DOC respiration may be responsible for a significant portion of DIC in this basin. Using an isotope and major ion mass balance approach to constrain the contributions of carbonate and silicate weathering and DOC respiration, we estimate that up to 29% of DIC is derived from DOC respiration in some parts of the Fraser River basin. Overall, these results indicate close coupling between the cycling of DOC and DIC, and that carbon is actively processed and transformed during transport through the river network.

Elastic electron scattering with CH2Br2 and CCl2Br2: The role of the polarization effects

We present elastic electron scattering cross sections with holmethane molecules CH2Br2 and CCl2Br2 in the low energy region ranging from 0.01 to 20 eV. The calculations are performed with R-matrix method in static-exchange plus polarization (SEP) and close-coupling (CC) approximations. The integral, differential, and momentum transfer cross sections are calculated. The convergence of the obtained cross sections is checked at four different levels of SEP approximation. The predicted positions of the resonances agree well with available results. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. We found that the polarization has a substantial effect on the cross sections, and this effect becomes even more important for lower impact energies.

Ab Initio Study of Single- and Double-Electron Capture Processes in Collisions of He2+ Ions and Ne Atoms

The single- and double-electron capture (SEC, DEC) processes of He2+ ions colliding with Ne atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling method. Total and state-selective SEC and DEC cross sections are presented in the energy region of 2 eV/u to 20 keV/u. Results show that the dominant reaction channel is Ne+(2s2p 6 2 S) + He+(1s) in the considered energy region due to strong couplings with the initial state Ne(2s 22p 6 1 S) + He2+ around the internuclear distance of 4.6 a.u. In our calculations, the SEC cross sections decrease initially and then increase whereby, the minimum point is around 0.38 keV/u with the increase of collision energies. After considering the effects of the electron translation factor (ETF), the SEC cross sections are increased by 15%–25% nearby the energy region of keV/u and agree better with the available results. The DEC cross sections are smaller than those of SEC because of the larger energy gaps and no strong couplings with the initial state. Due to the Demkov-type couplings between DEC channel Ne2+(2s22p 4 1 S) + He(1s 2) and the dominating SEC channel Ne+(2s2p 6 2 S) + He+(1s), the DEC cross sections increase with increasing impact energies. Good consistency can also be found between the present DEC and the experimental measurements in the overlapping energy region.

Electron Scattering Cross-Section Calculations for Atomic and Molecular Iodine

Cross sections for electron scattering from atomic and molecular iodine are calculated based on the R-matrix (close-coupling) method. Elastic and electronic excitation cross sections are presented for both I and I2. The dissociative electron attachment and vibrational excitation cross sections of the iodine molecule are obtained using the local complex potential approximation. Ionization cross sections are also computed for I2 using the BEB model.

Quantum Dynamics of Rotational Transitions in CN (X2Σ+) by H+ Collisions

Collisional cross-sections of inelastic rotational excitations of CN in its ground electronic state (X2Σ+) by H+ scattering are studied by the exact quantum mechanical close-coupling (CC) method at very low collision energies (0–600 cm−1) relevant to interstellar atmospheres. Ab initio rigid rotor potential energy surface computed at MRCI/cc-pVTZ level of accuracy has been employed. Rate coefficients for the rotational excitations have also been calculated. The obtained results are compared with previous theoretical calculations and analyzed whether proton collisions could be significant sources for rotationally excited CN as a possible source for cosmic microwave background of about 3 K from the interstellar media.

Knowledge Discovery by Analyzing the State of the Art of Data-Driven Fault Detection and Diagnostics of Building HVAC

The automated fault detection and diagnostics (AFDD) of heating, ventilation, and air conditioning (HVAC) using data mining and machine learning models have recently received substantial attention from researchers and practitioners. Various models have been developed over the years for AFDD of complete HVAC or its sub-systems. However, HVAC complexities, which partly have roots in its close coupling nature and interrelated dependencies, mean that understanding the relationship between faults and the suitability of the techniques remains an unanswered question. The literature analysis and interactive visualization of the data collected from the past implementation of AFDD models can provide useful insight to further explore this question by applying artificial intelligence (AI). Association rule mining (ARM) is deployed by this paper, using the frequent pattern (FP) growth algorithm to generate frequent fault sets for most common HVAC faults from the body of AFDD models developed in the literature to represent the status quo. A new model is developed for common HVAC faults and the techniques most frequently used to detect and diagnose them. A recommender system is developed using the ARM model to extract knowledge from the body of knowledge of HVAC data-driven AFDD in the form of rule-sets that reflect the associations. Findings of this review paper can significantly help civil and building engineers, as well as facility managers, in better management of building HVAC systems.

An overview of thermotransport in fluorite-related ionic oxides

In this overview, we summarize the phenomenon of thermotransport (the close coupling of mass transport and heat transport) in two fast ion conductors: yttria-doped zirconia and gadolinia-doped ceria. We focus on two recent molecular dynamics calculations using the Green-Kubo formalism. We show that the Onsager thermotransport cross coefficient (mass-heat coupling) is negative, meaning that oxygen ions would drift, in principle, to the hot side in a temperature gradient. Simulation results presented in this overview show reasonable agreement with available experimental data for thermal conductivity. Results of this study suggest that the coupling between mass and heat transport in oxygen ion electrolytes could have significant effect for practical applications.

Benchmark PhotoIonization Cross-Sections of Neutral Scandium from the Ground and Excited States

The B-spline R-matrix method has been used to investigate cross-sections for photoionization of neutral scandium from the ground and excited states in the energy region from the 3d and 4s valence electron ionization thresholds to 25 eV. The initial bound states of Sc and the final residual Sc+ ionic states have been accurately calculated by combining the multiconfiguration Hartree-Fock method with the frozen-core close-coupling approach. The lowest 20 bound states of Sc I belonging to the ground 3d4s2 and excited 3d24s, 3d24p, 3d4s4p, 4s24p, and 3d3 configurations have been considered as initial states. The 81 LS final ionic states of Sc+ belonging to the terms of 3p63d2, 3p63d4l (l = 0–3), 3p63d5l (l = 0–3), 3p63d6s, 3p64s2, 3p64s4l (l = 0–3), 3p64s5l (l = 0–1), and 3p64p2 configurations have been included in the final-state close-coupling expansion. The cross-sections are dominated by complicated resonance structures in the low energy region converging to several Sc+ ionic thresholds. The inclusion of all these final ionic states has been noted to significantly impact the near-threshold resonance structures and background cross-sections. The important scattering channels for leaving the residual ion in various final states have been identified, and the 3d electron ionization channels have been noted to dominate the cross-sections at higher photon energies.

Low-Energy Elastic Electron Scattering from Helium Atoms

We reinvestigate a key process in electron-atom collision physics, the elastic scattering of electrons from helium atoms. Specifically, results from a special-purpose relativistic polarized-orbital method, which is designed to treat elastic scattering only, are compared with those from a very extensive, fully ab initio, general-purpose B-spline R-matrix (close-coupling) code.