Mixed Length Research Articles

Thomas–Reiche–Khun populations in X–CH 3 and X–C 2H 5 series of molecules

Calculations of nuclear electric shieldings, equivalent to dipole moment geometric derivatives, and related to atomic polar tensors, are presented for X–CH 3 and X–C 2H 5 molecules with X=NH 2, OH and F. The electric shielding tensors satisfy a constraint for the electrostatic equilibrium, i.e., the mixed length–acceleration Thomas–Reiche–Khun sum rule, which gives important indications on the reliability of theoretical predictions of IR intensities and leads to the definition of atomic populations. Numerical evidence was found for the additivity and transferability of atomic populations, within the X-substituted alkane series.

Deviations from 1:1 Compositions in Self-Assembled Monolayers Formed from Adsorption of Asymmetric Dialkyl Disulfides on Gold

Alkanethiolate monolayers on polycrystalline gold, formed by typical solution self-assembly conditions with immersion in dilute ethanolic solution of asymmetric dialkyl disulfides CH3(CH2)n-1SS(CH2)15CH3 (n = 4, 8, 12), were found to consist predominately of CH3(CH2)15S- moieties. This observation shows that large deviations from expected 1:1 compositions can occur. The data support an exchange mechanism involving dissociative chemisorption of the S−S moiety and a subsequent replacement of the shorter chains by the longer ones via short chain disulfide or thiolate desorption and readsorption of mixed chain length disulfide. The efficiency of the substitution process increases with increasing length difference of the hydrocarbon chains in the respective disulfides.

Langmuir-Blodgett Film Stability Via Atomic Force Microscopy

Abstract Langmuir-Blodgett (LB) films of fatty acid salts are inherently unstable due to the fundamental incompatibility of the asymmetric monolayer film transferred from the water surface with the centrosymmetric equilibrium form of the fatty acid bulk crystal. One consequence of this incompatibility is that fatty acid salt films deposited by the LB technique do not remain as flat and uniform films, but reorganize into bilayer step islands. By using mixed chain length films, the islands and holes had distinct heights that suggest this reorganization occurs by a bulk folding of the layers rather than a molecular reorganization of the molecules. We have studied cadmium arachidate (CdA) LB films, varying the substrate used, the number of layers deposited, and the time the film spends under the aqueous subphase. All films were imaged in air with an Atomic Force Microscope (AFM).

Thermal and Tectonic History of the Ordos Basin, China: Evidence from Apatite Fission Track Analysis, Vitrinite Reflectance, and K-Ar Dating

Apatite fission track analysis, vitrinite reflectance data, and K-Ar dating of Permian-Carboniferous and Mesozoic core samples have been successfully integrated to reconstruct the thermal and tectonic history of the Ordos basin, China. Apatite fission track ages of Carboniferous-Jurassic sedimentary rocks range between 3 and 137 Ma, and are significantly younger than the stratigraphic ages. Confined fission track lengths demonstrate exclusively mixed length distribution, indicating complex thermal history. The data suggest that the samples must have all experienced higher paleotemperatures in the past. Mean vitrinite reflectance values (R0) of the Triassic rocks range from 0.61 to 1.06%, giving a high coalification gradient of 0.36%/km and suggesting a high paleothermal gradient of 57°C/km. Permian-Carboniferous rocks have Ro values on the order of 1.0-3.0%, and locally up to 4.0-6.0%. Some high R0 values coincide with positive gravity and magnetic anomalies. K-Ar dating on Permian-Triassi samples reveals distinct illitization at 170-160 Ma, during which a thermal event occurred due to subsurface magmatic intrusion related to the early Yanshanian movement. The petroleum source rocks of the Upper Triassic experienced peak temperatures ranging from 90 to 160°C, corresponding to the oil window, and Permian-Carboniferous source rocks were heated to more than 150°C, passing through and out of the gas window. Due to rapid uplift and erosion in response to the rise of the Qinghai-Tibet plateau associated with the Asia-India collision and the Himalayan orogeny, cooling has taken place at least since approximately 23 Ma. The difference in the rate and amount of uplift between the eastern and western parts of the basin resulted in differential uplift and the present-day s ructural pattern of the basin.

Mesothelial cell proliferation: a nonspecific response to lung injury associated with fibrosis.

An early proliferative response of mesothelial and subpleural cells has been reported in animals after inhalation or intratracheal (I.T.) instillation to the lung of long asbestos fibers, which also induce pulmonary fibrosis. To determine whether this cell proliferation is directly related to asbestos exposure or is a nonspecific response to injury, we examined [3H]thymidine (3HT) uptake by cells at the pleura after exposing mice to 5 days of hyperoxia, to intravenous (I.V.) (3 mg) or I.T. (0.15 mg) bleomycin, to I.T. (1 mg) silica, and to I.T. (0.1 mg) crocidolite asbestos of mixed length. All exposures induced acute lung injury, as shown by high levels of protein in lavage fluid. After hyperoxia, the percentage of total lung cells labeled by 3HT in autoradiographs was high for only a few days, as repair took place with no increase in fibroblast growth and no subsequent development of fibrosis. Particle or bleomycin exposure induced a prolonged increase in 3HT uptake with enhanced fibroblast labeling over a 4- to 6-wk period. In each case, labeled subpleural cells, mainly fibroblasts, increased up to 10-fold in the first 2 to 4 wk. At the same time, 3HT uptake by mesothelial cells ranged from 1.4 to 3% compared with almost zero in controls and in oxygen-exposed mice after a few days upon return to air. These results indicate that mesothelial and subpleural cell proliferation occurs after various types of injury to the lung. The close temporal association between 3HT uptake by mesothelial cells and fibroblasts during the reparative phase suggests that mesothelial cells may respond to the same cytokines that trigger interstitial fibrosis.

Topographical investigations of human ovarian-carcinoma polymorphic epithelial mucin by scanning tunnelling microscopy.

Human polymorphic epithelial mucin is a high-molecular-mass glycoprotein that associates to provide protection to the epithelial-cell surface and may afford the malignant cell a selective advantage for growth. The scanning-tunnelling-microscopy micrographs obtained in the present study identify the purified human ovarian-carcinoma polymorphic epithelial mucin glycoproteins as rod-shaped molecules of mixed length. The dimensions of the individual molecules range from 25 to 45 nm in length and are 3-4 nm in width. The images further suggest that lateral association of the rods occurs.

Temperature Evolution of a Smectic Liquid Crystal with Inner Degrees of Freedom

Abstract A statistical model of the smectic A mesophase with inner degrees of freedom (MIDF-model) is formulated in which the interlayer interaction of molecules is described in the McMillan approximation and the intramolecular interaction account is fulfilled in the pseudo-spin approximation. In terms of the variational Feynman-Bogoljubov principal the MIDF-model free energy depending on three order parameters: orientational (P2), conformational (1−x) and mixed translationally-orientational (ωP 2⟨ ones and also on four control parameters: a sizeless temperature (t), effective length (ε), rigidity (y) and characteristic size of central core (a) of molecules is calculated. By means of numerical methods the investigation of equilibrium equations is fulfilled which allows to separate qualitatively different versions of the smectic liquid crystal temperature evolution to which different versions of dependence ⟨P2⟩ x and ⟨ωP 2⟩ on t, of the state diagrams in coordinates “ε–γ” and of the phase diagrams in variables “t-y” of the MIDF-model correspond. A fundamentally new result of the paper is an establishing of the conditions at which a conformational disorder increase causes successive isostructural phase transitions in stability ranges of the system's smectic and nematic states. Those are realized in accordance to one of following schemes: coSm (conformationally ordered smectic)—cdSm (conformationally disordered smectic)—N (nematic)‒IL (isotropic liquid), coSm‒cdSm‒IL and Sm‒coN (conformationally ordered nematic)‒cdN (conformationally disordered nematic)—IL which are found experimentally in lipids, alkylammonium compounds, p-n−octyloxybenzoic acids.

Statistical thermodynamics of flexible-chain surfactants in monolayer films: Mixtures of different chain lengths

Recently, a simple mean-field theory was developed to describe structural and thermodynamic properties of fluid phases in monolayer films of flexible-chain surfactants [J. Chem. Phys. 91, 4423, 4431 (1989)]. This approach is extended here to examine films of mixed chain length. The high-density (LC-LE) phase transition predicted for the single component monolayers is found to exhibit nonideal mixing behavior, ranging from positive azeotropy to phase separation (in the LC phase) as the difference in chain lengths is increased. In contrast, the phase diagram in the LE-G transition region is predicted to exhibit almost ideal behavior, with a nearly linear bubble-point curve.

Statistical Thermodynamics of Phase Transitions in Surfactant Monolayer Films

ABSTRACTA lattice statistical mechanical method has recently been developed and used to predict structural and thermodynamic properties of fluid phases of surfactant monolayer films of uniform chain length. This mean-field approach is extended here to examine films of mixed chain length. As in the earlier work, a fluid-fluid (LC-LE) phase transition is predicted to occur at high surface densities. This transition is found to exhibit non-ideal mixing behavior, ranging from positive azeotropy to phase separation (in the LC phase) as the difference in chain lengths increases. In contrast, the phase diagram in the liquid-gas (LEG) transition region is predicted to exhibit almost ideal behavior, with a nearly linear bubble-point curve.

Mixing behavior of symmetric chain length and mixed chain length phosphatidylcholines in two-component multilamellar bilayers: evidence for gel and liquid-crystalline phase immiscibility.

The mixing behavior of symmetric chain length and mixed chain length phosphatidylcholines in two-component multilamellar bilayers has been investigated by high-sensitivity differential scanning calorimetry. Phase diagrams have been constructed for two-component bilayers composed of C(18)C(18)PC and either C(18)C(16)PC, C(18)C(14)PC, C(18)C(12)PC, or C(18)C(10)PC. It is found that C(18)C(18)PC-C(18)C(16)PC and C(18)C(18)PC-C(18)C(14)PC mixed bilayers exhibit complete miscibility of the components in both the gel and liquid-crystalline phases. Whereas this mixing is observed to be nearly ideal for the C(18)C(18)PC-C(18)C(16)PC binary system, the intermixing of the lipids is highly nonideal in the gel phase of the C(18)C(18)PC-C(18)C(14)PC binary mixture. The C(18)C(18)PC-C(18)C(12)PC and C(18)C(18)PC-C(18)C(10)PC mixed bilayers are characterized by partial immiscibility of the phosphatidylcholine components in the bilayer gel phase. Over a large compositional range, these bilayers appear to consist of phase-separated regions of interdigitated and noninterdigitated gel phases. In addition, the C(18)C(18)PC-C(18)C(10)PC two-component bilayer displays a limited region of liquid-liquid immiscibility in the liquid-crystalline bilayer phase. The phase separation of the mixed chain length phosphatidylcholines revealed in these mixed bilayers may represent a three-dimensional phase separation of the lipid components where the phosphatidylcholines are both laterally separated within the plane of the bilayer and conformationally coupled across the bilayer. Such phase-separated domains could have profound effects on membrane structure and function if they were to occur in biological membranes.

The Role of Intensive Seismic Reflection Processing in Understanding the Offshore Otway Basin

The offshore Otway Basin is a difficult area for seismic exploration, due to the presence of shallow, high-velocity carbonates. Both the shallow and deep-water parts of the basin were investigated in a single regional survey done by the Bureau of Mineral Resources vessel Rig Seismic in 1985. The survey and processing parameters used to obtain the best results for such a wide-ranging survey are discussed. A mixed group length cable was used to improve shallow resolution. By using an intensive approach to processing, good results were obtained on the shallow water shelf areas, and deep crustal features were well resolved in deeper areas. The processing sequence used F-K filtering in the shot domain routinely, with signature deconvolution and 2D filtering for multiple suppression in deep water.

Effect of Mixed-Chain-Length Surfactants on Fluid Displacement in Porous Media by In-Situ Foaming Process

Summary A laboratory study was designed to improve fluid displacement efficiency in porous media by an in-situ foaming process and to determine the effect of mixed surfactant chain length on surface properties of foaming solutions, bubble size, breakthrough time, and fluid displacement in porous media. We screened various mixed surfactant systems, such as sodium dodecyl sulfate and alkyl alcohols. Maximum breakthrough time and fluid displacement efficiency were observed when both components of the mixed foaming system possessed the same chain length. Results were compared with data obtained using water, brine, and sodium dodecyl sulfate alone. The microscopic studies revealed that the order of bubble size measured outside the porous medium for various mixed surfactants was indeed maintained in a micromodel. The increase in the porous medium length improved breakthrough time and fluid displacement efficiency in sandpacks and in Berea cores. Mixed surfactant systems showed a correlation among surface properties of foaming solutions, bubble size, break-through time, and fluid displacement efficiency in a porous medium. Maximum foaminess, minimum bubble size, minimum surface tension, maximum surface viscosity, maximum breakthrough time, and maximum fluid displacement efficiency were observed when the two components of the surfactant system had the same chain length.

Isolation from a methanogenic ferulate degrading consortium of an anaerobe that converts methoxyl groups of aromatic acids to volatile fatty acids

An anaerobic, non-motile, rod shaped bacterium is described which cleaves the phenylether bonds of methoxylated aromatic substrates to give the corresponding hydroxy aromatic derivatives and mixed volatile fatty acids, chain length, C1, C2 and C4. The bacterium was isolated from an anaerobic digestor fed with contents from a wood fiber to alcohol fermentation plant, using anaerobic rolltube medium with ferulate as the carbon and energy source. Moles fatty acid produced per 100 mole of methoxyl group of aromatic substrate fermented were approximately: acetate, 14; butyrate, 18; and formate, 15. For the fermentation of equimolar amounts of methoxylated aromatic compounds, growth yields were proportional to the number of methoxylated groups per molecule, and the amount of cells per methoxyl group did not alter when phenylacrylate derivatives were used as substrates. The organism was unable to reduce the side-chain double bond of phenylacrylate derivatives. Coculture of the bacterium on ferulate with Methanospirillum hungatei, or Desulfovibrio in the presence of SO 4 = resulted in no nett production of formate, and small quantities of methane and sulfide were produced respectively. The isolate utilized glucose, fructose, and lactate, but not methanol or H2−CO2 as growth substrates. Lactate, butyrate, acetate, formate and small quantities of H2 were produced from glucose fermentation. No reduction of SO 4 = or NO 3 - occurred during fermentation of glucose or methoxylated aromatics and no growth occurred in the presence of oxygen.

Deuterium NMR study of chain disorder in lamellar phases of mixed chain length

Deuterium NMR study of chain disorder in lamellar phases of mixed chain length

Linear alkylbenzene sulfonates in the prevention of vagrant dye pick‐up on polyester textile fabric during laundering

AbstractThe unwanted pick‐up of low levels of vagrant dyes during washing of textile fabrics can be a significant contributor to long‐term polyester appearance degradation. Fabric appearance loss from pick‐up of small quantities of a standard yellow dye are measured on both optically brightened and unbrightened polyester. Linear alkylbenzene sulfonate (LAS) surfactant micelles act as effective dye scavengers, reducing the level of dye pick‐up by the fabric substantially. The efficacy of LAS as a dye scavenger is quantified as a function of alkyl chain length and use concentration. Dye scavenging ability per unit weight of LAS increases with increasing molecular weight and decreasing critical micelle concentration (cmc). Dye scavenging of up to 80% of the transferable dye is achieved at high LAS concentrations. Results with C9, C11, C13 and C15 single homolog alkyl chain lengths, and with several mixed chain length blends are presented.

The turbulence kinetic energy budget in convective conditions

AbstractData from the 1973 Minnesota atmospheric boundary layer experiment are used to investigate details of the turbulence kinetic energy budget in convective conditions. Surface layer results are presented in nondimensional form and compared with conclusions from earlier Kansas data. Above the surface layer the terms are nondimensionalized using mixed layer similarity length and velocity scales and compared with indications from other recent experiments.

The turbulence kinetic energy budget in convective conditions

Data from the 1973 Minnesota atmospheric boundary layer experiment are used to investigate details of the turbulence kinetic energy budget in convective conditions. Surface layer results are presented in nondimensional form and compared with conclusions from earlier Kansas data. Above the surface layer the terms are nondimensionalized using mixed layer similarity length and velocity scales and compared with indications from other recent experiments.

The correlation of photometric signals derived from in vivo red blood cell flow in microvessels

Photometric signals generated by projecting the in vivo image of microvessels of cat omentum onto two photodetectors aligned in the direction of blood flow were cross-correlated as a function of time delay and progressively greater detector spacing. It was found that the degree of correlation decreases as a function of increasing detector separation, in an approximate exponential fashion, until correlation is no longer discernible. The persistence of downstream correlation is inversely proportional to blood velocity and vessel diameters when these are greater than 30 μm and is directly proportional to velocity and diameter in smaller vessels. These results were related to a “correlation length” analogous to the mixed length theory for turbulent flows. It is proposed that a similarly defined parameter be established for blood flow in the microvascular system, and utilized to compare flowing blood in normal and abnormal conditions.

Direct determination oftrans unsaturation in triglycerides by infrared spectrophotometry

AbstractA differential infrared spectrophotometric method is described for the determination oftrans unsaturation in fats. The method utilizes absorption at 965 cm蜢1, due to the C蜢H out‐of‐plane deformation vibrations oftrans unsaturated compounds. The method is rapid, accurate, and directly applicable to the determination oftrans unsaturation in triglycerides. It is applicable to samples which contain low concentrations oftrans acids (down to 2%) and also to samples with fatty acids of mixed chain length.

The separation of glycerides of mixed fatty acid chain length by glass paper chromatography

A chromatographic separation on glass fiber paper of mixed glycerides of acetic, butyric, stearic, palmitic, and oleic acids in solvents consisting of 2% and 5% ether in isoöctane has been described. In general, glycerides containing fatty acids of increasing chain length tend to move further up the chromatograms than those of shorter chain length.