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Various Experiments (various + experiment)
Selected AbstractsConodont affinity and chordate phylogenyBIOLOGICAL REVIEWS, Issue 2 2000PHILIP C. J. DONOGHUE ABSTRACT Current information on the conodonts Clydagnathus windsorensis (Globensky) and Promissum pulchrum Kovács- Endrödy, together with the latest interpretations of conodont hard tissues, are reviewed and it is concluded that sufficient evidence exists to justify interpretation of the conodonts on a chordate model. A new phylogenetic analysis is undertaken, consisting of 17 chordate taxa and 103 morphological, physiological and biochemical characters; conodonts are included as a primary taxon. Various experiments with character coding, taxon deletion and the use of constraint trees are carried out. We conclude that conodonts are cladistically more derived than either hagfishes or lampreys because they possess a mineralised dermal skeleton and that they are the most plesiomorphic member of the total group Gnathostomata. We discuss the evolution of the nervous and sensory systems and the skeleton in the context of our optimal phylogenetic tree. There appears to be no simple evolution of free to canal-enclosed neuromasts; organised neuromasts within canals appear to have arisen at least three times from free neuromasts or neuromasts arranged within grooves. The mineralised vertebrate skeleton first appeared as odontodes of dentine or dentine plus enamel in the paraconodont/euconodont feeding apparatus. Bone appeared later, co-ordinate with the development of a dermal skeleton, and it appears to have been primitively acellular. Atubular dentine is more primitive than tubular dentine. However, the subsequent distribution of the different types of dentine (e.g. mesodentine, orthodentine), suggests that these tissue types are homoplastic. The topology of relationships and known stratigraphic ranges of taxa in our phylogeny predict the existence of myxinoids and petromyzontids in the Cambrian. [source] Structural information from quadrupolar nuclei in solid state NMRCONCEPTS IN MAGNETIC RESONANCE, Issue 3 2006Sharon E. Ashbrook Abstract Solid-state NMR has become the method of choice for determining details of molecular-level structure in heterogeneous systems. Though spin-1/2 nuclei still form the core of most such studies, quadrupolar nuclei are increasingly being used. This review assesses what is currently possible, from achieving high-resolution spectra for quadrupolar nuclei (a prerequisite for most structure determination work), to forming correlation spectra which give qualitative details of spatial proximity of nuclei and the determination of internuclear distances, between quadrupolar spins and quadrupolar and spin-1/2 nuclei. Examples are given of each method discussed, and the advantages and disadvantages of the various experiments for different possible applications are assessed. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 183,248, 2006. [source] In situ substrate conversion and assimilation by nitrifying bacteria in a model biofilmENVIRONMENTAL MICROBIOLOGY, Issue 9 2005Armin Gieseke Summary Local nitrification and carbon assimilation activities were studied in situ in a model biofilm to investigate carbon yields and contribution of distinct populations to these activities. Immobilized microcolonies (related to Nitrosomonas europaea/eutropha, Nitrosomonas oligotropha, Nitrospira sp., and to other Bacteria) were incubated with [14C]-bicarbonate under different experimental conditions. Nitrifying activity was measured concomitantly with microsensors (oxygen, ammonium, nitrite, nitrate). Biofilm thin sections were subjected to fluorescence in situ hybridization (FISH), microautoradiography (MAR), and local quantification of [14C]-bicarbonate uptake (beta microimaging). Nitrifying activity and tracer assimilation were restricted to a surface layer of different thickness in the various experiments (substrate or oxygen limitation). Excess oxygen uptake under all conditions revealed heterotrophic activity fuelled by decay or excretion products during active nitrification. Depth limits and intensity of tracer incorporation profiles were in agreement with ammonia-oxidation activity (measured with microsensors), and distribution of incorporated tracer (detected with MAR). Microautoradiography revealed a sharp individual response of distinct populations in terms of in-/activity depending on the (local) environmental conditions within the biofilm. Net in situ carbon yields on N, expressed as e, equivalent ratios, varied between 0.005 and 0.018, and, thus, were in the lower range of data reported for pure cultures of nitrifiers. [source] Classification of leaf imagesINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2006Chia-Ling Lee Abstract There are tremendous content-based retrieval systems. Most of them are applied to general image databases. Some were proposed for specified databases such as texture databases, ancient paintings, document image databases, digital mammography, face image databases, etc. However, there are fewer for plant databases. Plants are used in various fields such as in foodstuff, medicine, and industry. Recently, plant is important for environment protection. On the other hand, the problem of plant destruction becomes worse in the few years. We should train people to know about plants, in turn, to treasure and protect them. In addition to the limited number of expert botanists, the convenient content-based retrieval system for plant is necessary and useful, since it can retrieve related information and knowledge from plant database for the query leaf so as to facilitate fast learning of plants. In this study, a leaf database is constructed and a classification method for leaves is proposed. Most approaches for leaf classification in literature used contour-based features. The proposed method tries to use region-based features. The reasons are that region-based features are more robust than contour-based features since significant curvature points are hard to find. Those features adopted include aspect ratio, compactness, centroid, and horizontal/vertical projections. The effectiveness of the proposed method has been demonstrated by various experiments. On the average, our method has the classification accuracy for 1-NN rule as 82.33% and the recall rate for 10 returned images as 48.2%, while the contour-based method has 37.6% and 21.7%, respectively. © 2006 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 16, 15,23, 2006 [source] Dispersion interactions in density-functional theoryJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2009Erin R. Johnson Abstract Density-functional theory (DFT) allows for the calculation of many chemical properties with relative ease, thus making it extremely useful for the physical organic chemistry community to understand and focus on various experiments. However, density-functional techniques have their limitations, including the ability to satisfactorily describe dispersion interactions. Given the ubiquitous nature of dispersion in chemical and biological systems, this is not a trivial matter. Recent advances in the development of DFT methods can treat dispersion. These include dispersion-corrected DFT (using explicit, attractive dispersion terms), parameterized functionals, and dispersion-correcting potentials, all of which can dramatically improve performance for dispersion-bound species. In this perspective, we highlight the achievements made in modeling dispersion using DFT. We hope that this will provide valuable insight to both computational chemists and experimentalists, who aim to study physical processes driven by dispersion interactions. Copyright © 2009 John Wiley & Sons, Ltd. [source] Rising burden of immature sheep ticks (Ixodes ricinus) on red grouse (Lagopus lagopus scoticus) chicks in the Scottish uplandsMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2004A. D. Kirby Abstract., The sheep tick Ixodes ricinus (L.) (Acari: Ixodidae) is an ectoparasite of major economic and pathogenic importance in Scotland. Its distribution in the Scottish uplands is assumed to be governed by the abundance and distribution of its definitive hosts (deer and sheep) and climatic variables such as temperature and rainfall. As the numbers of its major host in Scotland, red deer, have increased dramatically and climatic conditions have become more favourable, the level of parasitism could have been expected to rise. We use data gathered from tick counts on over 4000 red grouse chicks Lagopus lagopus scoticus Latham (Galliformes: Tetraonidae) in various experiments over the past 19 years to ascertain whether the intensity and prevalence of parasitism has been increasing. From 1985 to 2003 the average tick burden of a parasitized red grouse chick has grown from 2.60 ± 1.12 ticks per chick to 12.71 ± 1.44. Over this period the percentage of chicks of a given brood parasitized has also increased from 4 ± 2% to 92 ± 3%. The possible implications of this increase in parasitism for red grouse production are discussed. [source] | |||||||||||||