Modeling the adsorption of U(VI) onto animal chitin using coupled mass transfer and surface complexation

This paper reports the development of a treatment system, using animal chitin as a passive biosorbent, for removing U(VI) from aqueous waste streams. An integral part of this system is a model that provides for the optimization of the treatment system through simulation of U(VI) removal efficiency based on the characteristics of the influent waste stream. The model accounts for changing solution matrix conditions through the coupling of surface complexation and mass transfer models. Complexation of U(VI) by chitin surface sites was modeled using FITEQL. Application of FITEQL in the “forward” mode provided the sorbed and aqueous phase concentrations needed for the mass transfer model. The mass transfer model was derived for both batch and continuously stirred tank reactor (CSTR) configurations using Fick's Law, reactor mass balances and rate law expressions. The coupled model was successfully validated using CSTR data at pH 6.5 and rate constants determined from batch sorption experiments. The CSTR configuration yields a steady-state, eighty percent U(VI) removal for 1 μM influent U(VI) with a solution-phase pH of 6.5 and 3.9 g l⁻¹ chitin.     

Frequency-Dependent Streaming Potentials

An experimental apparatus and data acquisition system was constructed to measure the streaming potential coupling coefficients as a function of frequency. The purpose of the experiments was to measure, for the first time, the real and imaginary portion of streaming potentials. In addition, the measured frequency range was extended beyond any previous measurements. Frequency-dependent streaming potential experiments were conducted on one glass capillary and two porous glass filters. The sample pore diameters ranged from 1 mm to 34 μm. Two frequency-dependent models (Packard and Pride) were compared to the data. Both Pride's and Packard's models have a good fit to the experimental data in the low- and intermediate-frequency regime. In the high-frequency regime, the data fit the theory after being corrected for capacitance effects of the experimental setup. Pride's generalized model appears to have the ability to more accurately estimate pore sizes in the porous medium samples. Packard's model has one unknown model parameter while Pride's model has four unknown model parameters, two of which can be independently determined experimentally. Pride's additional parameters may allow for a determination of permeability. Copyright 2001 Academic Press.     

Quantum field theoretical methods in chemically bonded systems II

Summary Many-body perturbation theory is derived for chemical bonds. Paired quasiparticles represent the bonds. Products of the paired quasiparticles define a model Bardeen-Cooper-Schrieffer function. The pairing force is added as a model interaction to the self-consistent problem. The starting model is based on valency and adiabatic symmetry correlation. Symmetries are enforced by the model Hamiltonian. Perturbative corrections are expressed as ordinary Feynman diagrams. The number of diagrams needed is the same as for particle-hole theory.This work was supported in part by the U.S. Department of the Navy, Space and Naval Warfare Systems Command under Contract N00039-89-C-0001, and in part by NATO Research Grant 1861. It was presented, in part, at the A.C. Wahl Memorial Session, Molecular Spectroscopy Symposium, Columbus, Ohio, 1984; and Midwest Theoretical Chemistry Conference, Milwaukee, Wisconsin, 1985.     

The effect of ultrasound on the alkaline hydrolysis of nitrophenyl esters

Ultrasound was found to increase the rate of hydrolysis of a series of esters by up to 15%. No effect of molecular structure upon this enhancement was observed.     

Synthesis of 2-carboxy-4-methylazetidine. A novel isomeric analog of dl-proline

L-Azetidine-2-carboxylic acid is a naturally occurring azetidine currently used in the synthesis of abnormally high molecular weight polypeptides. The synthesis of 2-carboxy-4-methylazetidine is now reported which is a novel isomeric analog of dl -proline. Reaction of α,β-dibromo carbonyl ester with three molar equivalents of benzylamine yields 1-benzyl-2-carbomethoxy-4-methyl-azetidine. Hydrolysis of the latter compound with barium hydroxide yields 1-benzyl-2-carboxyl-4-methylazetidine which, if subjected to catalytic hydrogenation., yields the title compound in practical yield. The cis configuration is tentatively assigned to the title compound on the basis of previously published arguments.     

Preparation and X-ray crystal structures of mixed ligand complexes containing the S3N ligand

Reaction of Hg(S₇N)₂ with cis- PtCl₂(PR₃)₂ (PR₃ = PPh₃, PPh₂Me, PPHMe₂, PEt₃) in the presence of Na[PF₆] gives [Pt(S₃N)(PR₃)₂][PF₆] in 32–46% yield. The complexes have been characterized by IR, NMR and microanalyses. The X-ray crystal structures of two examples (PR₃ = PPh₂Me and PEt₃) show that the S₃N⁻ ligand coordinates in a bidentate fashion via two sulphur atoms.     

Minimizing broadband excitation under dissipative conditions

Optimal control theory is employed for the task of minimizing the excited-state population of a dye molecule in solution. The spectrum of the excitation pulse is contained completely in the absorption band of the molecule. Only phase control is studied which is equivalent to optimizing the transmission of the pulse through the medium. The molecular model explicitly includes two electronic states and a single vibrational mode. The other degrees of freedom are classified as bath modes. The surrogate Hamiltonian method is employed to incorporate these bath degrees of freedom. Their influence can be classified as electronic dephasing and vibrational relaxation. In accordance with experimental results, minimal excitation is associated with a negatively chirped pulses. Optimal pulses with more complex transient structure are found to be superior to linearly chirped pulses. The difference is enhanced when the fluence is increased. The improvement degrades when dissipative effects become more dominant.     

The Bohlmann-Rahtz route to functionalised pyridine scaffolds and their use in library synthesis

The Bohlmann-Rahtz reaction has been used to prepare 2,3,6-trisubstituted pyridines suitable for use in library synthesis. The synthesis of piperidine substituted nicotinic acid derivative 9 has been optimised and carried out on a large scale to give ca. 500 g of scaffold which was used in the generation of the pyridine library 11.     

The free \mathfrak{m} -lattice on the poset H

Let H={a ₀, a ₁, a ₂, b ₀, b ₁, b ₂} be the poset defined by a ₀<a ₂<a ₁, b ₀<b ₂<b ₁, a ₀<b ₁, and b ₀<a ₁. For an infinite regular cardinal , we describe the free -lattice on H. This continues the work of I. Rival and R. Wille who accomplished the same for =. In subsequent papers, we show how to apply this result to describe the free -lattice on a poset for a large class of posets, called slender posets.     

Improved detection of multi-phosphorylated peptides in the presence of phosphoric acid in liquid chromatography/mass spectrometry

In contrast to lower phosphorylation states (e.g. the tryptic monophosphopeptide FQpSEEQQQTEDELQDK from bovine beta-casein), the specific detection of multi-phosphorylated peptides (e.g. the tetraphosphopeptide RELEELNVPGEIVEpSLpSpSpSEESITR from tryptic digestion of bovine beta-casein) has often been problematic for liquid chromatographic mass spectrometric (LC/MS) analysis owing to their high affinity for adsorption to exposed surfaces. We observed an enhancement in the overall detection of phosphopeptides on addition of phosphoric acid (0.1-1.0%) to the sample solution; a 10-fold increase in sensitivity was determined for the detection of two tryptic phosphopeptides and also a significant improvement in the detection of the tetraphosphopeptide. Using capillary LC with ion trap tandem MS for detection and identification, the achievable detection limits were 50 fmol and 50 pmol for the monophosphopeptide and the tetraphosphopeptide, respectively. Phosphoric acid is believed to act as a blocking agent to available silanol groups on both the silica capillary surface and the C(18)-bonded stationary phase silica surface.