Stress development during drying of calcium carbonate suspensions containing carboxymethylcellulose and latex particles

Stress development during drying of coatings produced from aqueous dispersions of calcium carbonate particles in the presence and absence of organic binders was studied using a controlled-environment stress apparatus that simultaneously monitored drying stress, weight loss, and relative humidity. Specifically, the influence of two organic binders on drying stress evolution was investigated: (1) carboxymethylcellulose, a water-soluble viscosifying aid, and (2) a styrene-butadiene latex emulsion of varying glass transition temperature. The stress histories exhibited three distinct regions. First, a period of stress rise was observed, which reflected the capillary tension exerted by the liquid on the particle network. Second, a maximum stress was observed. Third, it was followed by a period of either stress decay or rise depending on the organic species present. Significant differences in stress histories were observed between coatings containing soluble and nonsoluble binders. Maximum drying stresses (sigmamax) of 0.2-0.5 MPa were observed for coatings produced from pure calcium carbonate or calcium carbonate-latex suspensions, whereas coatings with carboxymethylcellulose exhibited substantially higher sigmamax values of 1-2 MPa. Upon drying, these coatings were quite hygroscopic, such that cyclic variations in relative humidity induced large cyclic changes in residual stress.     

Protein analysis by mass spectrometry and sequence database searching: a proteomic approach to identify human lymphoblastoid cell line proteins

Lymphoblastoid cell lines correspond to in vitro EBV-immortalized lymphocyte B-cells. These cells display a suitable model for experiments dealing with changes in protein expression occurring upon B-cell differentiation, after drug treatment, or after inhibition of some transcription factors. For all these reasons we have undertaken an effort aimed at developing a hematopoietic cell line protein two-dimensional electrophoresis (2-DE) database, containing B-lymphoblastoid 2-DE maps. In this work, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) peptide mass fingerprinting analysis was adopted for protein identification. The peptide mass fingerprinting identification and the sequence coverage obtained on colloidal Coomassie blue (CBB) stained gel was close to that obtained using zinc-imidazole staining. Everything considered, CBB being more comfortable for subsequent spot manipulations, CBB staining was chosen for identification of a larger number of polypeptides. The results suggest that reticulation of the gel can interfere preventing the uptake of the enzyme during the in-gel digestion step. Consequently, low molecular mass proteins appear more difficult to identify by mass fingerprinting. Finally, the information provided in this study allows the construction of a new annoted reference map of human lymphoblastoid cell proteins. Among the identified proteins 60% were not yet positioned on 2-DE maps in three of the most important well-documented databases. The annoted map will be accessible via Internet on the LBPP server at URL:http:// www-smbh.univ-paris13.fr/lbtp/index.htm.     

Coordination d'anions organophosphores: 2eme partie. Perturbations provoquées par les coordinats “halogéno” et “pseudohalogeno” dans des complexes du zinc(II). Étude par spectro

Infrared and nuclear magnetic resonance spectroscopy data are presented for a series of complexes [ZnXL], where L^? denotes the {(C₂H₅O)₂POCHCOCH₂NR₂}^? anion with R = CH₃ (La^?) or C₂H₅ (Lb^?) and X a halogen or pseudohalogen. The infrared data reveal that the splitting of the absorption v(P → O) depends on the nature of X^? and is interpreted in terms of a crystal effect. The following order Cl^? < NCO^? ~ Br^? < I^? < NCS^? < NCSe^? is consistent with the ligand size. Nonequivalent protons on a given methylene group and nonequivalent methyl or ethyl groups bonded to nitrogen are detected by NMR spectroscopy of deuterochloroform solutions of these complexes. With La^?, the rate of exchange increases in the order NCO^?, Cl^?, Br^?, X^? (X^? = I^?, NCS^?, NCSe^?). The kinetic parameters for exchange of nonequivalent N(CH₃)₂ groups were determined.     

A many-body diagrammatic theory of rotation–vibration spectra

A many-body diagrammatic perturbation theory of rotation–vibration spectra is elaborated. The present approach is based on two many-body techniques, namely on the second quantization formalism (a rotating–vibrating molecule is formally treated here as a system of interacting vibrons, obeying the Bose–Einstein statistics) and the many-body diagrammatic theory of a model Hamiltonian, initially suggested in the microscopic theory of nuclei and in the last decade very frequently exploited in the accounting for the correlation effects in many electron systems. In the framework of this theory, the rotation–vibration energies are determined as the eigenvalues of a finite-dimensional model eigenproblem.     

Unipolar conductivity of donor or acceptor solutions

Donor or acceptor compounds in apolar organic solvents become charged at a high-field strength electrode and are driven to a surrounding low-field strength electrode of opposite sign. At 10 kV per cm the solutions conduct 3–7 times better when the highly charged electrode is positive in donor solutions. The opposite situation occurs in acceptor solutions.     

516—Synthetic and biological membranes

Biological cell membranes are compared to artificially produced permselective membranes. In spite of the difference in their thickness and electric resistance it is shown that they are similar in many important aspects, and the behaviour of synthetic membranes can explain very many points in the behaviour of cell membranes, especially axons. It is stressed that it is seldom necessary to assume unproven channels in biological membranes which are specific in the transport of a single ion species. Most of the phenomena of selectivity, opening and closing of such membranes can be explained by the influence of pH on membrane sites, by their poisoning with higly charged and/or large counter-ions. The borderline between two oppositely charged regions of a mosaic membrane opens up because it can be traversed by both positive and negative ions and permselectively is lost. Bipolar membranes rectify the current. Amphoteric membranes undergo very complex changes in conducting properties and permselectively with pH, especially when allowance is made for the weakly dissociated sites contained within these membranes. It is suggested that black lipid membranes made in the laboratory could be used to elucidate new points of similarity if they were used under similar conditions to our technical membranes.     

Matched/Mismatched interaction of a cyclic hexapeptide with ion pairs containing chiral cations and chiral anions

The binding of a chiral quaternary ammonium ion to a cyclopeptide containing aromatic amino acid subunits is affected not only by the configuration of the cation but also by the configuration of the chiral counterion. Analysis of the binding equilibria shows that complex formation involves interaction of the whole ion pair with the host indicating that steric requirements of the anion influence complex geometry and stability.     

Study of ion transport processes in soils by radioabsorption method

The transport processes of Na⁺, K⁺, Cs⁺, Ca²⁺, Zn²⁺, Mn²⁺, Fe³⁺ and HPO ₄ ²⁻ ions were studied in soils by radioabsorption method. The effective diffusion coefficients varied in the interval of 10⁻¹⁶–10⁻¹⁰ m²s⁻¹. The effective diffusion coefficient of Ca²⁺, Co²⁺, Zn²⁺ and Fe³⁺ ions increased by several orders of magnitude as a result of the addition of a complex forming agent.     

Charge distributions and chemical effects. XXXIV. Concepts involved in an approximate,but accurate,description of bond energies

The concepts underlying the definition of bond energies in terms of potentials at the nuclei are outlined. The theory is rooted, first, in a definition of the energy, E_i, of “atom” i in the molecule in terms of the potential energy, V(i, mol), of nucleus Z_i in the field of all the electrons and nuclei of the molecule: E_i = Krn:x-wiley:00207608:media:QUA560260514:tex2gif-stack-1" loading="lazy" class="section_image" src="/cms/asset/09e19081-76ba-4df5-a14a-2c51b70090a7/tex2gif-stack-1.gif"> V(i, mol). The Krn:x-wiley:00207608:media:QUA560260514:tex2gif-stack-2" loading="lazy" class="section_image" src="/cms/asset/a5fa0b7e-ef45-4cae-88d8-6022dfa031e0/tex2gif-stack-2.gif"> parameter, which is not required to be a constant in the derivation of the energy expression describing the contribution of an ij bond, turns out to be virtually constant for each atomic species—a situation which is exploited in numerical applications. Second, the Hellmann—Feynman theorem is applied in the calculation of the derivative, δΔErn:x-wiley:00207608:media:QUA560260514:tex2gif-stack-3" loading="lazy" class="section_image" src="/cms/asset/6ab5be1f-7336-43f8-95a0-6c39ebe2f400/tex2gif-stack-3.gif">/δZ_i, of the atomization energy, ΔErn:x-wiley:00207608:media:QUA560260514:tex2gif-stack-4" loading="lazy" class="section_image" src="/cms/asset/ccdef1bc-948a-4733-a8d5-3c3897572cec/tex2gif-stack-4.gif">, using (i) the exact quantum-chemical definition of ΔErn:x-wiley:00207608:media:QUA560260514:tex2gif-stack-5" loading="lazy" class="section_image" src="/cms/asset/663ff2a4-0c86-4cb6-89d6-24339cdb9782/tex2gif-stack-5.gif"> and (ii) the view that ΔErn:x-wiley:00207608:media:QUA560260514:tex2gif-stack-6" loading="lazy" class="section_image" src="/cms/asset/9fe879ab-caad-4051-9f85-3e89c530a50b/tex2gif-stack-6.gif"> is the sum of bond energy contributions, ε_ij, plus a small interaction between nonbonded atoms. The individual bond energies derived in this manner necessarily depend on local charges at the bond-forming atoms. Numerical applications illustrate how this new bond-energy formula provides a simple link between typical saturated, olefinic, acetylenic, and aromatic hydrocarbons.     

Theoretical studies on the conformation of saccharides

Conformations of 2-methoxytetrahydropyran as a model for the six-membered ring in aldopyranosides have been calculated by the PCILO method using the algorithm of the conjugated gradient to optimize the geometry. The calculated geometry of the fourteen basic forms of 2-methoxytetrahydropyran was found to be in agreement with the available data obtained by X-ray diffraction of pyranosides. The results indicate differences in the geometry of 2-methoxytetrahydropyran resulting from the change of the axial vs. equatorial position of the methoxyl group. These changes are particularly meaningful in the values of bond angles and they are in agreement with the anomeric and exoanomeric effects. The experimentally found differences in the energies of an axial (⁴ C ₁) and equatorial (¹ C ₄) conformer, rc="/content/g5153547514u8w05/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">G = 2.9–3.7 kJ/mol, and the dipole moment, rc="/content/g5153547514u8w05/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0"> = 1.20 ± 0.05 D (1D = 3.33 10^–30mAs) agree well with the calculated values rc="/content/g5153547514u8w05/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">E = 3.18 kJ/mol and c="/content/g5153547514u8w05/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">> = 1.18 D which, in turn, suggest that the axial conformer is preferred over the equatorial one by a ratio a:e = 78:22.