Recent patterns of change in vegetation structure and tree composition of British broadleaved woodland: evidence from large-scale surveys

Evidence is presented of widespread changes in structure and species composition between the 1980s and 2003–2004 from surveys of 249 British broadleaved woodlands. Structural components examined include canopy cover, vertical vegetation profiles, field-layer cover and deadwood abundance. Woods were located in 13 geographical localities and the patterns of change were examined for each locality as well as across all woods. Changes were not uniform throughout the localities; overall, there were significant decreases in canopy cover and increases in sub-canopy (2–10 m) cover. Changes in 0.5–2 m vegetation cover showed strong geographic patterns, increasing in western localities, but declining or showing no change in eastern localities. There were significant increases in canopy ash Fraxinus excelsior and decreases in oak Quercus robur/petraea. Shrub layer ash and honeysuckle Lonicera periclymenum increased while birch Betula spp. hawthorn Crataegus monogyna and hazel Corylus avellana declined. Within the field layer, both bracken Pteridium aquilinum and herbs increased. Overall, deadwood generally increased. Changes were consistent with reductions in active woodland management and changes in grazing and browsing pressure. These findings have important implications for sustainable active management of British broadleaved woodlands to meet silvicultural and biodiversity objectives.

Comments on some recent measurements of anomalously steep N2O and O3tracer spectra in the stratospheric surf zone

Recent aircraft measurements, primarily in the extratropics, of the horizontal variance of nitrous oxide (N2O) and ozone (O3) in the middle stratosphere indicate that horizontal spectra of the tracer variance scale nearly as k−2, where k is the spatial wavenumber along the aircraft flight track [Strahan and Mahlman, 1994; Bacmeister et al., 1996]. This spectral scaling has been regarded as inconsistent with the accepted picture of stratospheric tracer motion; large-scale quasi-two-dimensional tracer advection typically yields a k−1 scaling (i.e., the classical Batchelor spectrum). In this paper it is argued that the nearly k−2 scaling seen in the measurements is a natural outcome of quasi-two-dimensional filamentation of the polar vortex edge. The accepted picture of stratospheric tracer motion can thus be retained: no additional physical processes are needed to account for deviations from the Batchelor spectrum. Our argument is based on the finite lifetime of tracer filaments and on the “singularity spectrum” associated with a one-dimensional field composed of randomly spaced jumps in concentration.

Independent fusions and recent origins of sex chromosomes in the evolution and diversification of glass knife fishes (Eigenmannia)

The genus Eigenmannia comprises several species groups that display a surprising variety of diploid chromosome numbers and sex-determining systems. In this study, hypotheses regarding phylogenetic relationships and karyotype evolution were investigated using a combination of molecular and cytogenetic methods. Phylogenetic relationships were analyzed for 11 cytotypes based on sequences from five mitochondrial DNA regions. Parsimony-based character mapping of sex chromosomes confirms previous suggestions of multiple origins of sex chromosomes. Molecular cytogenetic analyses involved chromosome painting using probes derived from whole sex chromosomes from two taxa that were hybridized to metaphases of their respective sister cytotypes. These analyses showed that a multiple XY system evolved recently (<7 mya) by fusion. Furthermore, one of the chromosomes that fused to form the neo-Y chromosome is fused independently to another chromosome in the sister cytotype. This may constitute an efficient post-mating barrier and might imply a direct function of sex chromosomes in the speciation processes in Eigenmannia. The other chromosomal sex-determination system investigated is shown to have differentiated by an accumulation of heterochromatin on the X chromosome. This has occurred in the past 0.6 my, and is the most recent chromosomal sex-determining system described to date. These results show that the evolution of sex-determining systems can proceed very rapidly. Heredity (2011) 106, 391-400; doi:10.1038/hdy.2010.82; published online 23 June 2010

Ancestral polymorphism and recent invasion of transposable elements in Drosophila species

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Catálogo de publicaciones de CEPAL, ILPES, CELADE = Catalogue of publications of ECLAC, ILPES, CELADE

Publicación bilingüe

Catálogo de publicaciones de CEPAL, ILPES, CELADE = Catalogue of publications of ECLAC, ILPES, CELADE

Publicación bilingüe

Selección de documentos y publicaciones de la División de Desarrollo Social de la CEPAL = Selection of documents and publications of ECLAC's Social Development Division

Publicación bilingüe

Selección de documentos y publicaciones de la División de Desarrollo Social de la CEPAL: octubre-diciembre 1995 = Selection of documents and publications of ECLAC's Social Development Division: October-December 1995

Publicación bilingüe

Recent applications of analytical techniques for quantitative pharmaceutical analysis: A review

The intension of this paper was to review and discuss some of the current quantitative analytical procedures which are used for quality control of pharmaceutical products. The selected papers were organized according to the analytical technique employed. Several techniques like ultraviolet/visible spectrophotometry, fluorimetry, titrimetry, electroanalytical techniques, chromatographic methods (thin-layer chromatography, gas chromatography and high-performance liquid chromatography), capillary electrophoresis and vibrational spectroscopies are the main techniques that have been used for the quantitative analysis of pharmaceutical compounds. In conclusion, although simple techniques such as UV/VIS spectrophotometry and TLC are still extensively employed, HPLC is the most popular instrumental technique used for the analysis of pharmaceuticals. Besides, a review of recent works in the area of pharmaceutical analysis showed a trend in the application of techniques increasingly rapid such as ultra performance liquid chromatography and the use of sensitive and specific detectors as mass spectrometers.

From hard-peg to hard landing?: recent experiences of Argentina and Ecuador

Includes bibliography