Showing 1–12 of 57 results
A taxonomic revision of the tigers (Panthera tigris) of Southeast Asia
The taxonomic affiniرایگان!
The taxonomic affinity of Southeast Asian tigers is re-investigated. Specimens of four traditionally recognized subspecies are examined using various craniological methods, including multivariate craniometric and phenetic analysis. Sumatran tigers differ absolutely (100%) from the geographically neighbouring mainland form P.t.corbetti; the Javanese tiger is also 100% distinguishable from the Sumatran. They are therefore regarded as two distinct species (P.sumatrae, P.sondaica) under the Phylogenetic Species Concept (PSC). The Bali tiger is classified as a subspecies of the Javanese tiger, Panthera sondaica balica .
Biomimetic chromatophores for camouflage and soft active surfaces
Chromatophores are tرایگان!
Chromatophores are the pigment-containing cells in the skins of animals such as fish and cephalopods which have chromomorphic (colour-changing) and controllable goniochromic (iridescent-changing) properties. These animals control the optical properties of their skins for camouflage and, it is speculated, for communication. The ability to replicate these properties in soft artificial skin structures opens up new possibilities for active camouflage, thermal regulation and active photovoltaics. This paper presents the design and implementation of soft and compliant artificial chromatophores based on the cutaneous chromatophores in fish and cephalopods. We demonstrate artificial chromatophores that are actuated by electroactive polymer artificial muscles, mimicking the radially orientated muscles found in natural chromatophores. It is shown how bio-inspired chromomorphism may be achieved using both areal expansion of dielectric elastomer structures and by the hydrostatic translocation of pigmented fluid into an artificial dermal melanophore.
Developing a core collection of olive (Olea europaea L.) based on molecular markers (DArTs, SSRs, SNPs) and agronomic traits
Molecular markers (Sرایگان!
Molecular markers (SSR, SNP and DArT) and agronomical traits have been used in the world’s largest olive (Olea europaea L.) germplasm collection (IFAPA, Centre Alameda del Obispo, Cordoba, Spain) to study the patterns of genetic diversity and underlying genetic structure among 361 olive accessions. In addition the marker data were used to construct a set of core collections by means of two different algorithms (MSTRAT and PowerCore) based on M (maximization) strategy. Our results confirm that the germplasm collection is a useful source of genetically diverse material. We also found that geographical origin is an important factor structuring genetic diversity in olive. Subsets of 18, 27, 36, 45 and 68 olive accessions, representing respectively 5%, 7.5%, 10%, 12.5% and 19% of the whole germplasm collection, were selected based on the information obtained by all the data set as well as each marker type considered individually. According to our results, the core collections that represent between 19% and 10% of the total collection size could be considered as optimal to retain the bulk of the genetic diversity found in this collection. Due to its high efficiency at capturing all the alleles/traits states found in the whole collection, the core size of 68 accessions could be of special interest for genetic conservation applications in olive. The high average genetic distance and diversity and the almost equal representation of accessions from different geographical regions indicate that the core size of 36 accessions, could be the working collection for olive breeders.
Differential sensitivity of C3 and C4 plants to water deficit stress: Association with oxidative stress and antioxidants
The metabolic reasonرایگان!
The metabolic reasons associated with differential sensitivity of C3 and C4 plant species to water stress are not well understood. In the present study, 15-day-old wheat (Triticum aestivum) and maize (Zea mays) plants, representatives of C3 and C4 plants, respectively, were subjected to mild (–0.4 MPa), moderate (–0.8 MPa) and high (–1.5 MPa) water stress levels induced by PEG-6000 for 7 days under controlled conditions. The roots and leaves of these plant species were evaluated for oxidative damage and antioxidants along with stress injury (as electrolyte leakage), water content and abscisic acid. While at mild stress, both the plant species did not vary significantly from each other for stress injury, moderate and high stress levels caused considerably more damage to wheat as compared to maize. This was accompanied by more loss of water and chlorophyll by wheat relative to maize at these stress levels. ABA content remained unaffected at mild stress level in both the plant species but showed significantly higher content in roots and leaves of maize than wheat at moderate and high stress levels. The oxidative damage in terms of malondialdehyde and H2O2 content was markedly higher in wheat as compared to maize at moderate and high stress levels. Relatively, maize had significantly higher content of non-enzymatic (ascorbic acid and glutathione) and enzymatic antioxidants (ascorbate peroxidase, dehydroascorbate reductase and glutathione reductase, especially in its leaves). In contrast, wheat possessed more activity of catalase in its roots as well as leaves in comparison to maize. Superoxide dismutase activity showed little variation between the two plant species. Leaves of both the species experienced more damage than roots. These findings suggested that differential sensitivity of C3 and C4 plants to water stress appear to be partially governed by their ability to counter oxidative stress, pertinently involving ascorbic acid and glutathione .
Effect of physical form of forage on performance, feeding behavior, and digestibility of Holstein calves
The physical form ofرایگان!
The physical form of forage may influence rumen development and, consequently, the body weight gain ,dry matter (DM) consumption, digestibility, and welfare of dairy calves. The objective of this study was to determine the effect of 2 different physical forms of forage on performance, apparent digestibility, and feeding behavior of young calves. Twenty Holstein male calves (46.8 ± 1.2 kg) were randomly assigned at birth to 1 of 2 feeding treatments in which they were exposed to a mixed ration containing (on a DM basis) 90% crumb starter concentrate and either (1) 10% coarsely chopped (3 to 4 cm) grass hay (CRS; n = 10) or (2) 10% finely ground (2 mm) grass hay (FN; n = 10). All calves were offered 8 L/d of milk replacer (MR; 1.2 kg of DM) from birth; the amount of MR was progressively reduced after 5 wk to enable weaning by the end of wk 7. The study finished after wk 8. Consumption of the mixed ration, MR, and water was recorded daily, and calves were weighed twice weekly. Samples of feed and orts were taken in wk 7 and 8 for nutrient content analysis. Behavioral data for each calf were obtained for 2 h/d during wk 6 and 8, for a total observation time per animal of 28 h. Total feces were collected during wk 8 to determine apparent digestibility. Calves fed CRS had greater DM intake than those fed FN (2.70 vs. 2.45 ± 0.11 kg/d, respectively) during the week after weaning (wk 8). Body weight gain was similar between treatments; however, calves fed CRS tended to have a greater gain-to-feed ratio than calves fed FN (0.68 vs. 0.63 ± 0.02 kg of gain/kg of DM intake). No differences were observed in crude protein and acid detergent fiber consumption between treatments; however, calves fed CRS tended to consume more neutral detergent fiber than calves fed FN during the last week of the study (719.2 vs. 610.5 ± 25.84 g/d).
Effects of Cell Type and Culture Media on Interleukin-6 Secretion in Response to Environmental Particles
Cultured lung cellsرایگان!
Cultured lung cells provide an alternative to animal exposures for comparing the effects of different types of air pollution particles. Studies of particulate matter in vitro have reported proinflammatory cytokine signaling in response to many types of environmental particles, but there have been few studies comparing identical treatments in multiple cell types or identical cells with alternative cell culture protocols. We compared soil- derived, diesel, coal fly ash, titanium dioxide, and kaolin particles along with soluble vanadium and lipopolysaccharide, applied to airway-derived cells grown in submerged culture. Cell types included A549, BEAS-2B, RAW 264.7, and primary macrophages .The cell culture models (specific combinations of cell types and culture conditions) were reproducibly different in the cytokine signaling responses to the suite of treatments. Further, Interleukin-6 (IL-6) response to the treatments changed when the same cells, BEAS-2B, were grown in KGM versus LHC-9 media or in media containing bovine serum. The effect of changing media composition was reversible over multiple changes of media type. Other variables tested included culture well size and degree of confluence. The observation that sensitivity of a cell type to environmental agonists can be manipulated by modifying culture conditions suggests a novel approach for studying biochemical mechanisms of particle toxicity.
Effects on both the roots and shoots of soybean during dark chilling determine the nature and extent of photosynthesis inhibition
The relative contribرایگان!
The relative contribution of low soil and air temperatures towards the overall inhibition of hotosynthesis in soybean is still unclear. The mechanisms involved in the dark chilling-induced inhibition ofphotosynthesis were explored further in a chilling tolerant (Highveld Top) and ensitive (PAN809) soybean genotype in experiments where low soil temperatures were present (whole plant chilling, WPC) or absent (shoot-localised chilling, SC). Initially (after three nights of chilling) both the WPC and SC treatments induced the same symptoms in PAN809. These symptoms could thus be ascribed to chilling stress effects on the shoots. Typical symptoms included reduced CO2 assimilation capacity, inhibition of photosystem II function and lower chloroplast fructose-1,6-bisphosphatase (cFBPase) and ucrosephosphate-synthase (SPS) activity. When the nodulated root systems of PAN809 were also exposed to lowtemperatures (WPC treatment), additional constraints gradually developed, which were not observed inHighveld Top. Novel evidence is provided showing that the response in PAN809 is influenced by whether whole-plant or shoot-localised dark chilling occurs and that cFBPase is specifically targeted resulting insevere inhibition of CO2 assimilation capacity.
Electrocatalytic oxidation of some carbohydrates by poly(1-naphthylamine)/nickel modified carbon paste electrode
A method of generatiرایگان!
A method of generating a rapidly renewable and reproducible polymer coated electrode surface is proposed. This involves in situ electropolymerization at a monomer modified carbon paste electrode. A carbon paste electrode bulk modified with 1-naphthylamine was used to demonstrate this approach. Then Ni(II) ions were incorporated by immersion of the modified electrode in a 0.1 M Ni(II) ion solution. The electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)/Ni(II) couple even after potential 500 cycles. Also, cyclic voltammetric and chronoamperometric experiments showed that glucose was xidized at the surface of this Ni(II) dispersed polymeric modified carbon paste electrode. The electrode was successfully used in the electrocatalytic oxidation of various other carbohydrates. Finally, the electrocatalytic oxidation peak currents of all carbohydrates tested exhibited a good linear dependence on concentration and their quantification can be done easily.