Synthesis and properties of aminopropyl nucleic acids

Oligonucleotides that contain up to three aminopropyl nucleoside analogues have been synthesized. Dimers of aminopropyl adenine and thymidine were prepared and used as building blocks by applying phosphoramidite chemistry. Both R and S isomers of the aminopropyl nucleosides were used. This incorporation led to a reduction of thermal stability of double-stranded DNA. Furthermore, the (R)-adenine analogue, which yielded (S)-APNA, can be considered as a candidate for universal base pairing.     

Stress–Strain Behavior of Nicalon-Fiber-Reinforced Calcium Aluminosilicate Composites under Tensile Fatigue Conditions

The unusual stress–strain hysteresis loop shape exhibited by ceramic-matrix composites under cyclic loading has previously been explained as a result of either strain rate dependence of the frictional shear stress or crack closure. This investigation has determined that the response is due to neither mechanism. Instead, it is proposed that a variation of interfacial shear strength occurs during each cycle. A static coefficient of friction dominates immediately after loading or unloading. A much lower dynamic coefficient of friction operates once fiber sliding begins. This dynamic coefficient appears to be very dependent on surface roughness.     

Adhesion aspects of levulinic-acid-modified furan polymers to crystalline zinc phosphate metal surfaces

The nature of the interfacial interactions between functional levulinic-acid-modified furan resin coatings and crystalline zinc phosphate hydrate films deposited on carbon steel surfaces has been systematically investigated. The typical surface topography of the highly crystallized zinc phosphate films was found to be characterized by the presence of a dendritic microstructure array of interlocking triclinic crystals. This structure acts significantly to develop mechanical interlocking bonds with the functional blend polymer which penetrates into the open surface structure of the films. Both the thickness of deposition film and the polar H₂O molecules of hydrate at the outermost film surface sites play essential roles in wetting by the functional liquid resin. When the polarized furan polymers spread on the oxide film surfaces, the carboxylate groups derived from the levulinic ester and acid molecules react to form strong hydrogen bonds with the crystallized H₂O molecules on the hopeite film. This formation of hydrogen bonding was shown to be a major factor affecting the chemical intermolecular attractions. A formulation consisting of 95 parts furan to 5 parts levulinic acid was found to yield the optimum protective coating. More than 5 parts levulinic acid resulted in the transformation of the characteristics of the polymer film from hydrophobic to hydrophilic.     

Mobil Zeolite Catalysts for Monomers

It has been about 20 years since Plank, Rosinski, and Hawthorne reported their spectacular results with metal-modified zeolite cracking catalysts for more efficient production of gasoline [1]. This discovery has saved an estimated 200 million barrels of crude oil each year in the United States alone [2]. In 1972, a patent by Argauer and Landolt described the preparation of a member of a generation of new synthetic zeolites, called ZSM- 5. It was unique because of its high silica/alumina ratio and greatly reduced coking rates for reactions with hydrocarbons by comparison with known low silica zeolites [3]. This material was an early member of a series of over 50 synthetic zeolitic substances prepared in Mobil laboratories.     

Use of15N for fertilizer N recovery and N mineralization studies in semi-arid Kenya

Maize and beans were grown on a ferralsol at Kiboko, Kenya, with up to 120 kg N ha^–1. Within the 10 kg N ha^–1 plots,¹⁵N labelled fertilizer was applied in microplots. There was no significant response in yield to fertilizer N and labelled N recovery was low, being 7.5% or less in one season and 17.7% or less in the second season. Samples of Kiboko soil at four different water contents were incubated and the rate of gross N mineralization over 7 days was calculated, utilizing¹⁵N labelling of the mineral N. Gross N mineralization increased greatly with soil moisture and a fitted relationship between gross N mineralization rate and soil water content was obtained. Using measurements of soil water content at the field site, daily values of the soil N supply by gross mineralization were calculated. On average, modelled gross soil N mineralized could supply much (> 69%) of the N removed from the plots. It is suggested that the lack of response to fertilizer N may be explained by the coincidence of a high rate of N mineralization, and increased crop demand, caused by the onset of rain.     

Cellulose-binding domains: potential for purification of complex proteins

The endoglucanase CenA and the exoglucanase Cex from Cellulomonasfimi each contain a discrete cellulose-binding domain (CBD),at the amino-terminus or carboxyl-terminus respectively. Thegene fragment encoding the CBD can be fused to the gene of aprotein of interest. Using this approach hybrid proteins canbe engineered which bind reversibly to cellulose and exhibitthe biological activity of the protein partner. Alkaline phosphatase(PhoA) from Escherichia coli, and a ß-glucosidase(Abg) from an Agrobacterium sp. are dimeric proteins. The fusionpolypeptides CenA-PhoA and Abg-CBC_cex are sensitive to proteolysisat the junctions between the fusion partners. Proteolysis resultsin a mixture of homo- and heterodimers; these bind to celluloseif one or both of the monomers carry a CBD, e.g. CenA-PhoA/CenA-PhoAand CenA-PhoA/PhoA. CBD fusion polypeptides could be used inthis way to purify polypeptides which associate with the fusionpartner.     

Composition analysis of {alpha}-helices in thermophilic organisms

We present a statistical comparison of the amino acid compositionin a secondary structure element, the -helix, of proteins stableat high temperatures with those which are less so. This studyhas shown that the temperature-dependent Zimm-Bragg helix propagationvalue s is not a good predictor for the helix-forming tendencyof an amino acid in thermostable proteins. However, we haveshown that s, the change in s from 20 to 60°C, accuratelypredicts the direction of the probability shift for 15 aminoacids in thermostable protein a-helices, although it does notpredict the magnitude of that change. The residues tyrosine,glycine and glutamine show a significant increase in residencyin a-helices for thermostable proteins over their nonthermostablecounterparts. Significant decreases in -helix residency occurfor the residues valine, glutamic acid, histidine, cysteineand aspartic acid in proteins from thermophilic organisms. Aromaticinteractions, hydrogen bonding and a reduction of charge mayexplain the increase observed for tyrosine and glutamine andthe decrease in glutamic acid and aspartic acid, although packingconsiderations cannot be ruled out The only physical explanationfor the increase in glycine would seem to be its positive svalue     

Temperature-dependent resistivity from phonons in cuprate superconductors

The temperature dependence of the resistivity of the cuprate superconductors arising from phonon scattering is considered within standard Bloch-Gruneisen theory allowing for several different shapes of transport spectral functions _tr ² F(). In contrast to often made comments that linear resistivity is not characteristic of electron-phonon scattering, it is shown rather that it is more difficult to get muchnonlinearity from this theory except below 50–100 K, and in this low-T regime better solutions to the Boltzmann equation might be required. The reasons for the linear behavior are clarified, and the variations to be expected from possible coupling functions are explored. Possible origins of the nonlinear resistivity seen in YBa₂Cu₄O₈ and recently in YBa₂Cu₃O₇ are suggested, and effects not included specifically in these calculations are discussed. It is also pointed out that phonon contributions to the energy () dependence of quasiparticles, which is a closely related consequence of electron-phonon coupling, will differ significantly from the simple ² Fermi liquid behavior that is commonly assumed.     

CO2 process intensification of algae oil extraction to biodiesel

Algae-to-biodiesel processes are hindered by high costs and low energy return on investment.^1,2. Herein, three foci in research improve algae-to-biodiesel processes by: (1) reducing high installation and energy costs in the CO₂ sequestration, cultivation, and harvesting stages; (2) improving oil extraction and biodiesel generation; and (3) increasing utilization of the proteins in lipid-extracted biomass (e.g., for animal feed), as well as the omega-3 fatty acids for nutraceuticals and food supplements. A process is introduced that uses carbon dioxide to aid in all three of these foci. CO₂ is used first in the form of microbubbles to lyse algae cell walls, releasing triglyceride oils. CO₂ also aids with transesterification of these triglycerides using methanol. At low temperatures (353.15–368.15 K) and intermediate pressures (5–10 MMPa), carbon dioxide causes methanol to dissolve partially in the triglyceride phase and triglyceride to dissolve partially in the methanol phase, increasing the transesterification reaction rate. Due to the nondestructive nature of these processes, other metabolites can also be harvested providing improvements in both mass and economic efficiency with an overall sharp reduction in the modeled price of biodiesel.     

A New Perspective on Patterns of Aging in Europe by Education and Gender

In this paper, we use the concept of prospective age to illuminate patterns of aging by gender, and education in Europe. We find that, within countries, the patterns of aging of men and women with high education are comparatively similar to one another, but that the patterns of aging are quite dissimilar for men and women in the low education group. Across countries the patterns of aging become more similar as education levels increase. Thus, when we look across educational strata, we find increasing convergence in the pattern of aging both across countries and by gender within countries. The distinctive patterns of aging in the Eastern European countries are largely associated with the comparatively rapid aging of men in the low education category. If aging patterns by education persist, improvements in the education composition of Eastern European countries would result in the patterns of aging there becoming more similar to those in Western European countries.