A re-analysis of agricultural production and consumption: implications for understanding the British Iron Age

Patterning in the carbonized seed assemblages from Iron Age sites in Britain has led to the development of several explanatory models. The most influential of these, by Martin Jones, proposed that grain-rich assemblages represent producer sites and weed-/chaff-rich assemblages consumer sites. The assumptions underlying this model and the method of constructing the diagrams are discussed and a new approach is put forward, stressing the need for appropriate levels of analysis and interpretation. It is concluded that a predominance of grain-rich samples is far more likely to be an indicator of the scale of production and consumption, than a means of distinguishing between the two. A review of the evidence from Iron Age Britain indicates that grain-rich site assemblages primarily occur in the south of the country, and frequently co-occur with pits, used for the storage of surplus grain. Moreover, such pits are concentrated in hillforts. It is proposed that the grain stored in such pits may have been used in large communal feasts and that the hillforts functioned as locations for feasting.

Comparative testing of tangential microfiltration for microbial cultures

In an attempt to extend and intensify the productive periods of bioprocesses, a self-cleaning tangential filtration device was examined. Built into a special-design bioreactor, its cell retention was evaluated for continuous-flow operation with selected examples of bacteria (Escherichia coli), yeasts (Sacharomyces cerevisiae), and filamentous fungi (Aspergillus niger). Performance characteristics such as filtration rates and cell accumulation were assessed as a function of filter rotational speed, operating pressure, cultivation time, and microfilter type (i.e., membrane or porous metallic). The highest flux of cell-free filtrate for each culture type was achieved using a 0.45-micron membrane-covered microfilter. While the respective yeast (S. cerevisiae) and bacterial (E. coli) cell concentrations were enhanced by as much as 16- and 8-fold over the batch growth levels, the representative A. niger fungal cultivation was less satisfactory because of progressively declining filtration rates limited by hydraulically resistant layers of microbial surface growth quite resistant to in situ filter backflushing with gas. Maximum steady-state flux was independent of operating pressure, yet was enhanced at rotational speeds up to about 800 rpm. Higher speeds offered no further improvements. The overall fermentation process was limited by the moderate levels of attainable flux which restricted the feed and dilution rates. The maximum attainable stabilized fluxes were 26-40 L/m(2) x h.     

Structure and function of bordered pits: new discoveries and impacts on whole-plant hydraulic function

Bordered pits are cavities in the lignified cell walls of xylem conduits (vessels and tracheids) that are essential components in the water-transport system of higher plants. The pit membrane, which lies in the center of each pit, allows water to pass between xylem conduits but limits the spread of embolism and vascular pathogens in the xylem. Averaged across a wide range of species, pits account for > 50% of total xylem hydraulic resistance, indicating that they are an important factor in the overall hydraulic efficiency of plants. The structure of pits varies dramatically across species, with large differences evident in the porosity and thickness of pit membranes. Because greater porosity reduces hydraulic resistance but increases vulnerability to embolism, differences in pit structure are expected to correlate with trade-offs between efficiency and safety of water transport. However, trade-offs in hydraulic function are influenced both by pit-level differences in structure (e.g. average porosity of pit membranes) and by tissue-level changes in conduit allometry (average length, diameter) and the total surface area of pit membranes that connects vessels. In this review we address the impact of variation in pit structure on water transport in plants from the level of individual pits to the whole plant.     

Topography and functional information of plasma membrane

By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8±0.09 nm in diameter and 1.9±0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40―60 nm, and a range of 1.8―5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12―40 nm for their diameter and 0.7―2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 μm2. According to their size, we classified the invaginated pits into two types―larger pits measuring 139 nm in diameter and 7.2 nm in depth, and smaller pits measuring 96 nm in diameter and 2.3 nm in depth. On dehydration-induced dead pro-toplasts, the degree of polarization of plasma membranes decreased. Lipid molecular layers appeared relatively smooth, and the quantity of integral proteins reduced a lot. Invaginated pits were still de-tectable at the membrane surface, but due to dehydration-induced protoplast contraction, the orifice diameter of pits reduced, and their depth increased. Larger pits averagely measuring 47.4 nm in di-ameter and 31.9 nm in depth, and smaller pits measuring 26.5 nm in diameter and 43 nm in depth at average. The measured thickness of plasma membranes of mesophyll cells from winter wheat examined by AFM was 6.6―9.8 nm, thicker in regions covered with proteins.     

Environmental determinants of Great Cormorant (Phalacrocorax carbo) distribution in small man-made waterbodies – a case study of gravel pits in southwest France

In the Midi-Pyrénées region (southwest France), the increasing number of gravel pits has allowed the wintering of numerous species of waterbirds such as Great Cormorants (Phalacrocorax carbo). The debate about cormorant predation on fish stock has been sufficiently strong to have resulted in reductions in cormorant numbers by control shooting. In this context, cormorants were studied during winters 1996/1997 and 1997/1998 at two gravel pit sites in the Garonne floodplain. Human disturbances and fish densities were found to be the main parameters determining the abundance of fishing cormorants. This work will help to prompt further research and the development of a management strategy for this species.     

Wood anatomy of Polygonaceae: analysis of a family with exceptional wood diversity

Quantitative and qualitative data are presented for woods of 30 species of woody Polygonaceae. Wood features that ally Polygonaceae with Plumbaginaceae include nonbordered perforation plates, storeying in narrow vessels and axial parenchyma, septate or nucleate fibres, vasicentric parenchyma, pith bundles that undergo secondary growth, silica bodies, and ability to form successive cambia. These features are consistent with pairing of Plumbaginaceae and Polygonaceae as sister families. Wood features that ally Polygonaceae with Rhabdodendraceae include nonbordered perforation plates, presence of vestured pits in vessels, presence of silica bodies and dark-staining compounds in ray cells, and ability to form successive cambia. Of the features listed above, nonbordered perforation plates and ability to form successive cambia may be symplesiomorphies basic to Caryophyllales sensu lato . The other features are more likely to be synapomorphies. Wood data thus support molecular cladograms that show the three families near the base of Caryophyllales s.l. Chambered crystals are common to three genera of the family and may indicate relationship. Ray histology suggests secondary woodiness in Antigonon, Atraphaxis, Bilderdykia, Dedeckera, Eriogonum, Harfordia, Muehlenbeckia, Polygonum , and Rumex . Other genera of the family show little or no evidence of secondary woodiness. Molecular data are needed to confirm this interpretation and to clarify the controversial systematic groupings within the family proposed by various authors. Vessel features of Polygonaceae (lumen diameter, element length, density, degree of grouping) show an extraordinary range from xeromorphy to mesomorphy, indicating that wood has played a key role in ecological and habital shifts within the family; the diversity in ecology and habit are correlated with quantitative wood data.  © 2003 The Linnean Society of London. Botanical Journal of the Linnean Society , 2003, 141 , 25−51.     

Viscoelastic characteristics of protein solutions and the micromechanics of their motion in porous carriers

The interactions of model proteins with porous matrices in biosensors are considered. The viscoelastic properties of casein and albumin were assessed by a dynamic method of a piezoquartz resonator by applying thin layers of the studied solutions to a piezocrystal. The experimental data on the viscoelastic characteristics of protein solutions of various concentrations were compared with the characteristics of their tangential motion in the porous carriers of cellulose nitrate. It was demonstrated that the parameters of dynamic viscosity correlated with the motion time of the protein solutions in the porous polymeric carrier.     

Purification and Characterization of Clathrin from Bovine Brain

Abstract: Clathrin has been purified to electrophoretic homogeneity by initial extraction of clathrin from purified coated vesicle fraction, followed by column chromatographies with gel filtration. DEAE-cellulose, and hydroxylapatite and finally by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Antibody specific to clathrin has also been obtained. Two forms of native clathrin, fast and slow components, have been prepared to about 95% purity by hydroxylapatite column chromatography. Both fast and slow components are believed to represent two different aggregates of clathrin subunit because they comigrate in agarose electrophoresis. pH 7.4, and also migrate as clathrin subunit on SDS-PAGE with a molecular weight of 175,000. Furthermore, both components cross-react with antibody against purified clathrin and compete for antibody binding site with labeled fast component. The fast component can also be converted to the slow component. In addition to clathrin, two proteins of about 38,000 and 35,000 M.W. that consistently co-purified with native clathrin are probably also intrinsic to coated vesicle.