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Although females' mating with multiple males is widespread in socially monogamous species, its evolutionary significance is poorly understood. Tests of the hypothesis that socially monogamous females seek extra-pair copulations to increase the heterozygosity of their offspring have produced mixed results. Some of the inconsistency may be the result of technical limitations of the molecular analyses used. In a previous analysis using five microsatellite loci, we showed that in the House Wren (Troglodytes aedon) extra-pair sires had fewer alleles common to the population than did other nearby males that could have sired offspring but did not, suggesting a “rare male” effect (Masters et al. 2003, Proceedings of the Royal Society of London, Series B 270:1393–1397). We repeated the previous analysis, including an additional set of seven microsatellite loci. An analysis that used all 12 loci (both the original and additional loci) produced results suggesting that genotype affects extra-pair paternity....

A model is developed that describes the complicated rheology and morphology of thermoplastic polymers blended with relatively small amounts of liquid-crystalline polymers (LCPs). Such blends typically display properties superior to, but more complicated than, those of ordinary thermoplastic polymers. Viscosity predictions are obtained with this model that exhibit the wide range of behavior that is observed experimentally in these blended materials for both shear and elongational flows. For example, the viscosity-composition curve can display a minimum at low compositions of LCP, and the addition of an LCP to a thermoplastic polymer can result in a reduction in the shear viscosity but an increase in the elongational viscosity. Corresponding morphological descriptions are also obtained for the internal microstructure of the blends that provide information about the underlying causes of the complicated rheological behavior.

The efficiency of a screening programme for Down's syndrome is usually expressed in terms of the detection rate for a given false positive rate. Two programmes with approximately equal detection rates and false positive rates would then be regarded as being broadly equivalent. While this might be the case at a population level, we show in this paper that it may be far from true at the individual patient level. Different algorithms, or even different implementations of the same algorithm can lead to calculation of very different individual risks and can result in different decisions for individual patients. Even though two programmes might lead to the same number of referrals, they could be referring quite different women. We consider the effect of using different parameter values within an algorithm, different algorithms and alternative ways of estimating the gestational age-dependent medians of the marker values. We show that the combined effects of these factors could explain much of the range of risks reported in the UK National External Quality Assessment Scheme for Down's syndrome screening.

Supercritical fluid chromatography (SFC) has proven to be widely applicable for the separation of enantiomers on chiral stationary phases. Many of the chiral selectors utilized in gas and liquid chromatography have also been transferred to SFC. This article provides an overview of the types of separations reported on different classes of chiral stationary phases in SFC and includes comparisons of SFC to other chromatographic techniques. The importance of various chromatographic parameters in obtaining successful enantioseparations in SFC is also discussed.

Several benzodiazepines were enantioresolved on a new carbohydrate chiral stationary phase based on maltooligosaccharides. The role of organic modifier, ionic strength, pH and temperature are examined and the results are discussed. In general, selectivity and retention were found to decrease with increasing organic modifier concentration. The appearance of two peaks for diazepam suggests that the reported separations are based on separation of conformers and was supported using circular dichroism detection. Counterintuitively, resolution and enantioselectivity were found to improve with increasing temperatures.

Comparisons of liquid (LC) and supercritical fluid chromatography (SFC) were conducted using commercially available chiral stationary phases (CSPs) bearing three different types of chiral selectors. Chiral compounds of pharmaceutical and agricultural interest were used to probe advantages or limitations of SFC relative to LC for enantiomeric separations. Column equilibration and parameter optimization were generally accomplished more rapidly in SFC than in LC. Although improved resolution was often observed in SFC, analysis times were not always lower in SFC than in LC. In some instances, SFC provided separation capabilities not readily accessible in LC.

A comparison of liquid (LC) and sub- or supercritical fluid chromatography (SFC) was performed using naphthylethylcarbamoylated-β-cyclodextrin chiral stationary phases (NEC-CD CSPs). Compounds resolved in the normal-phase, reversed-phase and polar organic modes on the NEC-CD CSPs in LC were also separated on the same columns in SFC with a carbon dioxide-alcohol eluent. Advantages of SFC for chiral separations on these CSPs included simple eluents, rapid optimization of selectivity and improved resolution compared to LC results for the same columns. The effect of alcohol modifier was also investigated and the results provided insights into the chiral recognition mechanisms in SFC. The versatility of the NEC-CD CSPs in SFC was demonstrated by performing separations representative of the three distinct mobile phase modes in LC in a single analysis in SFC.

The retention behavior of polycyclic aromatic hydrocarbons (PAHs) in packed-column supercritical fluid chromatography (SFC) is studied for monomeric and polymeric C18 columns. Molecular shape discrimination (shape selectivity) is assessed through the use of Standard Reference Materials (SRMs), adn changes in selectivity are studied as a function of temperature, pressure, and mobile phase composition. Examples of separations of complex PAH isomer mixtures are presented, and guidelines are provided for modification and optimization of shape selectivity in SFC.

New chiral stationary bonded phases (CSPs) based on derivatized malto-oligosaccharides are reported. Chiral separations are reported for 3,5-dinitrobenzoyl-derivatized amines and amino acids as well as some 3,5-dinitrophenylcarbamoylated alcohols. These new CSPs incorporate a 1-(1-naphthyl)ethylcarbamate (NEC) moiety which introduces additional stereogenicity and provides a useful probe for investigating chiral recognition. The elution order, when known, was dependent upon the configuration of the NEC substituent; that is, the S enantiomers were retained longest on the S column and the R enantiomers were retained longest on the R column. Elution order from the RS column, when known, was the same as that observed for the S column. In most cases, retention correlated with bonded ligand concentration on the silica substrate. In general, the best enantioselectivities and resolution were obtained on the S column.

A method is proposed for the direct enantiomeric analysis of chiral drugs in human serum by HPLC. The method is based on a commercially available β-cyclodextrin bonded phase which incorporates diol as well as cyclodextrin moieties. The proteinaceous components of the serum, which are shown to elute with the void volume, are well separated from the enantiomeric analytes. This allows for the rapid determination of the enantiomeric composition of the drugs.

A significant number of the organic components of foods, flavorings, pharmaceuticals, and pesticides are chiral molecules (Ariens, 1988). The role of stereochemistry in biological processes was first recognized more than 100 years ago by Pasteur and van’t Hoff’Le Bel (Pasteur, 1901). Much of the stereoselectivity of these chemicals has remained shrouded in mystery, however, because techniques for chiral separations were not well developed. The fact that enantiomers exhibit identical physical and chemical properties in an achiral environment renders their separation extremely difficult.

New ultraviolet observations and archival spectra are presented for the bright disk of the galaxy NGC 4736 to derive the ultraviolet surface brightness profile. This is used to predict the appearance of such a galaxy at high redshift. The profiles in red light of 100 galaxies determined by S. Kent (1984) are used with assumed ultraviolet spectra to predict the isophotal diameters of these galaxies as a function of redshift. The results show that, for ground-based imagery, normal spiral galaxies should be resolvable to the largest redshifts (z roughly 1). For space-based imagery, much smaller but brighter galactic disks characterized by extensive star formation will be those resolved at the highest redshifts (z roughly 2.5).