Upscaling of conductivity of heterogeneous formations: General approach and application to isotropic media

The numerical simulation of flow through heterogeneous formations requires the assignment of the conductivity value to each numerical block. The conductivity is subjected to uncertainty and is modeled as a stationary random space function. In this study a methodology is proposed to relate the statistical moments of the block conductivity to the given moments of the continuously distributed conductivity and to the size of the numerical blocks. After formulating the necessary conditions to be satisfied by the flow in the upscaled medium, it is found that they are obeyed if the mean and the two-point covariance of the space averaged energy disspation function over numerical elements in the two media, of point value and of upscaled conductivity, are identical. This general approach leads to a systematic upscaling procedure for uniform average flow in an unbounded domain. It yields the statistical moments of upscaled logconductivity that depend only on those of the original one and on the size and shape of the numerical elements.The approach is applied to formations of isotropic heterogeneity and to isotropic partition elements. After a general discussion based on dimensional analysis, the procedure is illustrated by using a first-order approximation in the logconductivity variance. The upscaled logconductivity moments (mean, two-point covariance) are computed for two and three dimensional flows, isotropic heterogeneous media and elements of circular or spherical shape. The asymptotic cases of elements of small size, which preserve the point value conductivity structure on one hand, and of large blocks for which the medium can be replaced by one of deterministic effective properties, on the other hand, are analyzed in detail. The results can be used in order to generate the conductivity of numerical elements in Monte Carlo simulations.Nomenclature C covariance - e rate of dissipation of mechanical energy per unit weight of fluid - E total rate of energy dissipation in the flow domain - H overlap function - K hydraulic conductivity - K _G geometrical mean of conductivity - I integral scale - J=P mean head gradient - L characteristic size of - l characteristic size of also diameter of circle and sphere - n number of dimensions - P pressure head - Q total fluid discharge - S _A ,S _B inlet and outlet boundaries of flow domain - v velocity - Y logconductivity - characteristic scale of flow nonuniformity - autocorrelation function - ² variance - flow domain - partition element Overlining space averaged over - Ã upscaled quantity - â Fourier transform ofa     

Cluster chemical ionization and deuterium exchange mass spectrometry in supersonic molecular Beams

A cluster-based chemical ionization method has been developed that produces protonated molecular ions from molecules introduced through a supersonic molecular beam interface. Mixed clusters of the analyte and a clustering agent (water or methanol) are produced in the expansion region of the beam, and are subsequently ionized by “fly through” electron impact (EI) ionization, which results in a mass spectrum that is a combination of protonated molecular ion peaks together with the conventional EI fragmentation pattern. The technique is presented and discussed as a tool complementary to electron impact ionization in supersonic molecular beams. Surface-induced dissociation on a rhenium oxide surface is also applied to simplify the mass spectra of clusters and reveal the analyte spectrum. The high gas flow rates involved with the supersonic molecular beam interface that enable the easy introduction of the clustering agents also have been used to introduce deuterating agents. An easy-to-use, fast, and routine on-line deuterium exchange method was developed to exchange active hydrogens (NH, OH). This method, combined with electron impact ionization, is demonstrated and discussed in terms of the unique information available through the EI fragmentation patterns, its ability to help in isomer identification, and possible applications with fast gas chromatography-mass spectrometry in supersonic molecular beams.     

Symmetrical gas-phase dissociation of noncovalent protein complexes via surface collisions

Previous gas-phase dissociation experiments of protein-protein complexes have resulted in product ion distributions that are asymmetric by charge and mass, providing limited insight into the chemical nature of subunit organization and interaction. In these experiments, a symmetric charge distribution results from an "energy sudden" collision of protein-protein complexes with a surface, indicating that it may be possible to probe the suboligomeric structure of noncovalent complexes in the gas phase. It is proposed that energy sudden surface activation of cytochrome C homodimers results in dissociation without significant unfolding of one of the monomeric subunits. Previously proposed mechanisms for the dissociation of protein-protein complexes are discussed in the context of these results. These experiments demonstrate the potential to preserve the structural details of subunit interaction within a protein-protein complex and help elucidate the asymmetric nature of macromolecular dissociation in the gas phase.     

Laser desorption ionization of small molecules assisted by tungsten oxide and rhenium oxide particles

Inorganic metal oxides have shown potential as matrices for assisting in laser desorption ionization with advantages over the aromatic acids typically used. Rhenium and tungsten oxides are attractive options due to their high work functions and relative chemical inertness. In this work, it is shown that ReO₃ and WO₃, in microparticle (μP) powder forms, can efficiently facilitate ionization of various types of small molecules and provide minimized background contamination at analyte concentrations below 1 ng/µL. This study shows that untreated inorganic WO₃ and ReO₃ particles are valid matrix options for detection of protonatable, radical, and precharged species under laser desorption ionization. Qualitatively, the WO₃ μP showed improved detection of apigenin, sodiated glucose, and precharged analyte choline, while the ReO₃ μP allowed better detection of protonated cocaine, quinuclidine, ametryn, and radical ions of polyaromatic hydrocarbons at detection levels as low as 50 pg/µL. For thermometer ion survival yield experiments, it was also shown that the ReO₃ powder was significantly softer than α‐cyano‐4‐hydroxycinnaminic acid. Furthermore, it provided higher intensities of cocaine and polyaromatic hydrocarbons, at laser flux values equal to those used with α‐cyano‐4‐hydroxycinnaminic acid. Copyright © 2015 John Wiley & Sons, Ltd.     

Low Mass MS/MS Fragments of Protonated Amino Acids Used for Distinction of Their 13C- Isotopomers in Metabolic Studies

Glu, Gln, Pro, and Ala are the main amino acids involved in ammonia detoxification in mosquitoes. In order to develop a tandem mass spectrometry method (MS²) to monitor each carbon of the above isotopically-labeled ¹³C-amino acids for metabolic studies, the compositions and origins of atoms in fragments of the protonated amino acid should be first elucidated. Thus, various electrospray (ESI)-based MS² tools were employed to study the fragmentation of these unlabeled and isotopically-labeled amino acids and better understand their dissociation pathways. A broad range of fragments, including previously-undescribed low m/z fragments was revealed. The formulae of the fragments (from m/z 130 down to m/z 27) were confirmed by their accurate masses. The structures and conformations of the larger fragments of Glu were also explored by ion mobility mass spectrometry (IM-MS) and gas-phase hydrogen/deuterium exchange (HDX) experiments. It was found that some low m/z fragments (m/z 27–30) are common to Glu, Gln, Pro, and Ala. The origins of carbons in these small fragments are discussed and additional collision induced dissociation (CID) MS² fragmentation pathways are proposed for them. It was also found that small fragments (≤m/z 84) of protonated, methylated Glu, and methylated Gln are the same as those of the underivatized Glu and Gln. Taken together, the new approach of utilizing low m/z fragments can be applied to distinguish, identify, and quantify ¹³C-amino acids labeled at various positions, either in the backbone or side chain.      

Tests of a fiber-optic velocity transducer

A novel transducer is developed and tested. The transducer utilizes optical fiber to measure mean and instantaneous flow rates in turbulent flows, and is capable of detecting flow reversal. Calibration of the transducer is conducted in both air and water. The dynamic response of the transducer is tested against hot-wire anemometery in the wake flow of a circular cylinder over a wide range of Reynolds number.List of symbols C _D drag coefficient - D diameter of cylinder - d diameter of fiber - E modulus of elasticity of the fiber - e output voltage - F drag force per unit length of a cylinder - f frequency (Hz) - L length of the fiber cantilever - M magnification factor - m mass per unit length of the fiber - Re Reynolds number - q dynamic pressure (= 1/2 U ²) - U free stream velocity - density - v kinematic viscosity     

Transport of a Passive Scalar in a Stratified Porous Medium

A uniform and horizontal head gradient J is applied to a stratified formation whose given random conductivity K is function of the vertical coordinate x ₃ only. K is assumed to be stationary and of finite integral scale I _v. By Darcy's law, the velocity field V ₁(x ₃)=JK depicts a fluctuating shear flow. A solute body is injected instantaneously in the formation. In a Lagrangean framework, the second spatial moment of the mean concentration C(x,t) can be related to the one-particle trajectories variance X ₁₁(t,Pe) where Pe = V₁I_v/D _dT and _dT is the transverse pore-scale dispersion coefficient. X ₁₁ was determined in the past by Matheron and de Marsily (1980). The present study is concerned with determining the local concentration variance _C ² , that depends on the two-particles trajectories covariance Z ₁₁(t). The latter is derived exactly and langle Crangle and _C ² are determined by assuming normal or lognormal probability distribution of trajectories. The results are illustrated for small and very large (ergodic) solute plumes. For large travel time the concentration coefficient of variation at the center of the plume tends asymptotically to a constant value, unlike formations with finite horizontal correlation length of the hydraulic conductivity. The results may serve for benchmarking of numerical codes and in applications for short travel distances in highly anisotropic formations.     

Analysis of the reaction np → dπ+π− below 3.5 GeV/c

The reaction np → dπ⁺π^? was studied from threshold up to 3.5 GeV/c neutron beam momentum. Cross-section values for this reaction are evaluated as a function of the beam momentum. The deuteron production features and the enhancement observed in the dπ mass spectrum at 2.17 GeV are adequately described in terms of an OPE model and nucleon-nucleon final-state interactions.     

Cross sections and multiplicity distributions forK + p interactions at 70 GeV/c

Cross sections and charged multiplicity distributions forK ⁺ p interactions at 70 GeV/c are presented and compared withK ⁺ p data at other energies. Comparisons are also made with available π⁺ p,pp, andK ^? p data.