High resolution glass capillary columns with chemically bonded stationary phases: application to the gas chromatographic analysis of sterols and steroids in biological extracts

A new approach has been developed for the preparation of highly stable glass capillary columns using irreversible bonding of polysiloxane polymers to the glass surface. The general procedure involves (a) synthesis of reactive linear polysiloxanes from variously (alkyl, aryl) substituted dichlorosilanes through homologous or heterologous polymerization under alcaline aqueous conditions, and (b) covalent condensation of the polymers to a properly prepared glass capillary surface at high temperature. The principle has been first applied to the successful preparation of apolar gas chromatographic systems (methylpolysiloxanes), then extended to the obtention of polar systems (methyl phenyl polysiloxanes). The flexibility of the approach is demonstrated by the possibility of obtaining stationary phases of various and controlled polarity (i.e., extent of phenyl substitution), tailor-made to a given analytical problem. These gas Chromatographic systems appear to be remarkably stable both with time and temperature up to 300 C and compare favorably to existing systems for their high resolution properties. These columns have been satisfactorily used in the last years for the analysis of sterols and steroids of biological origin and most extensively in the study of urinary steroid metabolite in humans under pathological conditions.     

Nail surgery

Nail deformities may present as wither medical or cosmetic problems, often requiring surgical intervention. These deformities have a number of etiologic factors including infections, inflammatory disease processes, congenital abnormalities, trauma, tumors, and systemic diseases. This article discusses several nail problems and surgery techniques.     

Aureole nanofibers by electrospinning of PAMAM‐PEO solution

Poly(amido amine) (PAMAM) dendrimer‐polyethylene oxide (PEO) nanofibers as dendrimeric‐polymeric composite nanofibers were prepared via electrospinning of PEO solution containing PAMAM dendrimer. The resultant fibers were characterized by means of transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The morphology and thermal properties of PEO nanofibers with and without PAMAM dendrimer were compared and the effect of PAMAM concentration on morphology and thermal properties of the resultant fibers was studied. The fibers had a size range of about 400–1300 nanometer in diameter with aureole morphology in most regions. The phase change temperature, phase transition heat, and the crystallinity of the produced composite fibers were determined by DSC analyses. TGA was also used to confirm the presence of PAMAM and to determine the amount of it within the fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

New methods for enhancing fine acquisition in dual folding algorithm of long pseudo noise codes

Long code Direct Sequence Spread Spectrum is a good choice for applications where security and antispoofing ability of a spread spectrum connection is concerned. Due to long period of spreading code, acquisition is a challenge for these systems because a trade‐off between detection probability and acquisition time must be made. For confronting this challenge, various algorithms were proposed in the literature but almost all of them focus on expediting the coarse acquisition. In this paper, we consider the efficient dual folding algorithm for coarse acquisition level and propose 3 methods for enhancing the fine acquisition level leading to faster execution of overall acquisition algorithm. The methods are based on estimations from coarse acquisition level that are not used in conventional algorithms for fine acquisition, ie, zero padding. Theoretical expressions of 2 main comparison criteria in acquisition algorithms, ie, detection probability and mean acquisition time, are derived for conventional zero padding and each of the proposed method. Besides, a coarse estimate of resource consumption is provided by the number of floating point operations for each algorithm to make a useful comparison. Considering these 3 parameters, in comparison, the proposed methods surpass zero padding in 1, 2, or all of the 3 aspects. Simulation agrees well with analytical results.     

Random Crystal Field in a Mixed Spin <Emphasis Type="Italic">S</Emphasis> = 1/2 and <Emphasis Type="Italic">S</Emphasis> = 3/2 Ising Model by Renormalization Group Theory

In this work, we study the Ising model with mixed spins S = ?1/2 and S = ?3/2 on the hypercubic lattice and the random crystal field at the sublattice with S =?3/2 described by a two peaks law. To achieve this, we use an approximation of position space renormalization group (PSRG) namely Migdal-Kadanoff in which we use both the free energy derivative and the flow in the parameter space of the Hamiltonian. For all values of the random probability, the critical behavior is determined via the critical exponents at the second-order fixed points while at low temperatures; the discontinuities of the of the free energy derivative provide the positions of the first-order transitions. The introduction of a minimal amount of disorder causes a change in the phase diagram showing the relevance of disorder for d =?2 and d =?3. The second-order transition remains always with the same critical exponents as those of the pure model, and a new first-order transition appears at very low temperature. Also, a comparison with other similar works is given.     

Chemometric Characterization of Eight Monovarietal Algerian Virgin Olive Oils

Differences in triacylglycerol, fatty acid, squalene, and tocopherol compositions were demonstrated between 8 varieties of virgin olive oils (Aberkane, Aguenaou, Aharoun, Aimel, Bouchouk Guergour, Bouichret, Chemlal, and Sigoise) from Petite Kabylie area, north eastern Algeria. Fatty acid and triacylglycerol morphotypes characterized each variety. A principal component analysis, based on triacylglycerol, fatty acid, and squalene compositions, differentiates between varieties. Minor fatty acids and squalene, usually not taken into account individually in authentication studies, are strongly involved in this differentiation, whereas the discriminant power of tocopherols is weak. Soft Independent Modeling of Class Analogy classification using chemical compositions as variables showed a high potential to authenticate the varietal origin of Algerian virgin olive oils.     

Study of electrophysical characteristics of lead-natural rubber composites as radiation shields

The dependence of the attenuation of both gamma rays and neutrons on lead concentration in leaded-natural rubber composites incorporated with paraffin wax and boron carbide as radiation shields was investigated. Moreover, the dc conductivity and swelling characteristics of the rubber vulcanizates and the effect of aging on them were studied. It was found that samples of 18 mm thickness incorporated with 20 phr of B₄C and 60 phr of paraffin wax can reduce the fast neutron beams by about 50%. For slow neutrons, the reduction was about 46%. The attenuated γ-dose increased exponentially with increasing lead content.     

The pozzolanic reactivity of monodispersed nanosilica hydrosols and their influence on the hydration characteristics of Portland cement

This study reveals that the nanosilica hydrosols with higher specific surface areas had faster pozzolanic reactivity, especially at early ages; moreover, the results are indicative of the accelerating influence of nanosilicas and silica fume on the hydration of cement. Faster initial and final setting times observed for cement pastes containing nanosilicas are consequence of these mechanisms. However, less hydration degree of cement compared to the plain paste was observed at age of 7 days and after. This can be attributed to the entrapment of some of mix water in the aggregates of nanosilicas formed in cement paste environment, making less water available for the progress of cement hydration. The same mechanism is believed to be responsible for the reduction of flowability of cement pastes.