Analysis and parametric sensitivity of the behavior of overshoots in the concentration of a charged adsorbate in the adsorbed phase of charged adsorbent particles: practical implications for separations of charged solutes

In this work, an analysis of the parametric sensitivity of the overshoot in the concentration of the adsorbate in the adsorbed phase, which occurs under certain conditions during an ion-exchange adsorption process, is presented and used to suggest practical implications of the concentration overshoot phenomenon on operational policies and configurations of chromatographic columns and finite bath adsorption systems. The results presented in this work demonstrate and explain how the development of an overshoot in the concentration of the adsorbate in the adsorbed phase could be enhanced or suppressed by (i) varying the diffusion coefficient, D3, of the adsorbate relative to the diffusion coefficients, D1 and D2, of the cations and anions, respectively, of the background/buffer electrolyte, (ii) altering the initial surface charge density, delta0, of the charged adsorbent particles, (iii) varying the Debye length, lambda, and (iv) changing the initial concentration, Cd3(0), of the adsorbate in the bulk liquid of the finite bath. The influence of the pH and ionic strength, Iinfinity, of the liquid solution on the development of an overshoot in the concentration of the adsorbate in the adsorbed phase is also presented and discussed through the relationships of these parameters to delta0 and lambda, respectively. Furthermore, a detailed explanation of the effects of each parameter on the interplay between the diffusive and electrophoretic molar fluxes, as well as on the structure and functioning of the electrical double layer, which are responsible for the concentration overshoot phenomenon, is presented.     

General relationships for isovalent cation substitution into oxides with the rocksalt structure

Isovalent cation substitution into rocksalt oxides, MO, has been investigated using atomistic simulation. A strain related parameter, ε, is established that relates the size of a substitutional cation to the host lattice ion for which it has been substituted. This has allowed us to identify relationships between solution energy, defect volume and a strain parameter, which are general for any rocksalt oxide host lattice and as such are predictive for any combination of a divalent cation and rocksalt host lattice.     

Structure of neutron-rich Be and C isotopes

The structure of neutron-rich beryllium isotopes has been investigated using different heavy-ion-induced transfer reactions. In neutron transfer reactions, the population of final states shows a strong sensitivity to the chosen core nucleus, i.e., the target nuclei ⁹Be or ¹⁰Be, respectively. Molecular rotational bands up to high excitation energies are observed with ⁹Be as the core due to its pronounced 2α-cluster structure, whereas only a few states at low excitation energies are populated with ¹⁰Be as the core. For ¹¹Be, a detailed investigation has been performed for the three states at 3.41, 3.89, and 3.96 MeV, which resulted in the most probable spin-parity assignments 3/2⁺, 5/2^?, and 3/2^?, respectively. Furthermore, we have studied particle-hole states of ¹⁶C using the ¹³C(¹²C, ⁹C)¹⁶C reaction and found 14 previously unknown states. Using the ¹²C(¹²C, ⁹C)¹⁵C reaction, five new states were observed for ¹⁵C.     

Evidence for the ground-state resonance of 26O

Evidence for the ground state of the neutron-unbound nucleus (26)O was observed for the first time in the single proton-knockout reaction from a 82 MeV/u (27)F beam. Neutrons were measured in coincidence with (24)O fragments. (26)O was determined to be unbound by 150(-150)(+50) keV from the observation of low-energy neutrons. This result agrees with recent shell-model calculations based on microscopic two- and three-nucleon forces.     

Intertrimer and intratrimer metallophilic and excimeric bonding in the ground and phosphorescent States of trinuclear coinage metal pyrazolates: a computational study

The interactions present in cyclic trinuclear coinage metal pyrazolates were studied computationally. Cuprophilic interaction was found to bind the singlet ground state of the dimer of trimers [[Cu(Pz)](3)](2), overcoming electrostatic repulsion. The large variation in intertrimer separations found in the literature for coinage metal pyrazolates is consistent with the relatively weak metallophilic interaction. The emissive triplet excited-state geometry of [[M(Pz)](3)](2) is predicted by density functional calculations to show major geometric distortion caused by Jahn-Teller instability and excimeric M-M bonding. Large calculated Stokes' shifts, which are also observed for experimental models, are consistent with significant excited-state distortions for these materials. The major finding derived from the present study is that the intertrimer M...M contraction in the emissive T(1) state is much more than the intratrimer contraction in all [[M(Pz)](3)](2) models, giving rise to a lower T(1) --> S(0) phosphorescence energy in these models than in analogous monomer-of-trimer models. The observations made here point to a great potential for rationally tuning the emission properties of trinuclear coinage metal complexes through choice of the metal and ligands.     

Dense layers of vertically oriented WO3 crystals as anodes for photoelectrochemical water oxidation

Films of crystalline WO(3) nanosheets oriented perpendicular to tungsten substrates were grown by a surfactant-free hydrothermal method, followed by sintering. The films exhibit photoelectrochemical oxygen evolution at low overpotential.     

Purification,Characterization, and Structural Studies of a Sulfatase from Pedobacter yulinensis

Sulfatases are ubiquitous enzymes that hydrolyze sulfate from sulfated organic substrates such as carbohydrates, steroids, and flavones. These enzymes can be exploited in the field of biotechnology to analyze sulfated metabolites in humans, such as steroids and drugs of abuse. Because genomic data far outstrip biochemical characterization, the analysis of sulfatases from published sequences can lead to the discovery of new and unique activities advantageous for biotechnological applications. We expressed and characterized a putative sulfatase (PyuS) from the bacterium Pedobacter yulinensis. PyuS contains the (C/S)XPXR sulfatase motif, where the Cys or Ser is post-translationally converted into a formylglycine residue (FGly). His-tagged PyuS was co-expressed in Escherichia coli with a formylglycine-generating enzyme (FGE) from Mycobacterium tuberculosis and purified. We obtained several crystal structures of PyuS, and the FGly modification was detected at the active site. The enzyme has sulfatase activity on aromatic sulfated substrates as well as phosphatase activity on some aromatic phosphates; however, PyuS did not have detectable activity on 17α-estradiol sulfate, cortisol 21-sulfate, or boldenone sulfate.     

Organotransition-Metal Metallacarboranes. 46. Multidecker Sandwiches of the Cobalt Group Metals(,)(1)

The double-decker sandwich complex CpIr(2,3-Et(2)C(2)B(4)H(4)) (1a) was prepared via deprotonation of nido-2,3-Et(2)C(2)B(4)H(6) to its mono- or dianion and reaction with (CpIrCl(2))(2) in THF and isolated as a colorless air-stable solid; the B(4)-chloro derivative 1b was also obtained. Decapitation of 1a and 1b with TMEDA afforded colorless nido-CpIr(2,3-Et(2)C(2)B(3)H(5)) (2a) and its 4-chloro derivative 2b. Chlorination of 1a by Cl(2) or N-chlorosuccinimide gave the symmetrical species CpIr(2,3-Et(2)C(2)B(4)H(3)-5-Cl) (1c), which was decapped to yield nido-CpIr(2,3-Et(2)C(2)B(3)H(4)-5-Cl) (2c). The triple-decker complexes CpIr(2,3-Et(2)C(2)B(3)H(2)-4[6]-Cl)IrCp (3), an orange solid, and dark green CpIr(2,3-Et(2)C(2)B(3)H(2)-4[6]-Cl)CoCp (5) were prepared from 2a and nido-CpCo(2,3-Et(2)C(2)B(3)H(5)) (4a), respectively, by deprotonation and reaction with (CpIrCl(2))(2) in THF. Reaction of the 2c(-) anion with Rh(MeCN)(3)Cl(3) gave the dark green tetradecker complex [CpIr(Et(2)C(2)B(3)H(2)-5-Cl)](2)RhH (6). In an attempt to prepare a heterotrimetallic Co-Rh-Ir tetradecker sandwich, a three-way reaction involving the deprotonated anions derived from CpCo(2,3-Et(2)C(2)B(3)H(4)-5-Cl) (4b) and 2c with Rh(MeCN)(3)Cl(3) was conducted. The desired species CpCo(Et(2)C(2)B(3)H(2)Cl)RhH(Et(2)C(2)B(3)H(2)Cl)IrCp (7) and the tetradeckers [CpCo(Et(2)C(2)B(3)H(2)Cl)](2)RhH (8) and 6 were isolated in small quantities from the product mixture; many other apparent triple-decker and tetradecker products were detected via mass spectroscopy but were not characterized. All new compounds were isolated via column or plate chromatography and characterized via NMR, UV-visible, and mass spectroscopy and by X-ray crystal structure determinations of 1a and 3. Crystal data for 1a: space group C2/c; a = 28.890(5) ?, b = 8.511(2) ?, c = 15.698(4) ?, beta = 107.61(2) degrees; Z = 8; R = 0.049 for 1404 independent reflections having I > 3sigma(I). Crystal data for 3: space group P2(1)/c; a = 11.775(4) ?, b = 15.546(5) ?, c = 15.500(5) ?, beta = 103.16(3) degrees; Z = 4; R = 0.066 for 2635 independent reflections having I > 3sigma(I).