The International Bathymetric Chart of the Arctic Ocean (IBCAO): An Improved Morphological Framework for Oceanographic Investigations

The IBCAO initiative set out in late 1997 to assemble and merge all available bathymetric observations from northern regions, with the intent of constructing a reliable and up-to-date portrayal of the Arctic seabed in digital and printed form. In early 2000, a provisional grid and map were placed in circulation for public review and comment. Available for free downloading from a website hosted by the U.S. National Geophysical Data Center, these products won immediate acceptance from a broad spectrum of Arctic investigators who recognized the potential worth of the new information in a variety of applications ranging from straightforward map production to analysing the influence of underwater topography on ocean circulation. At the same time, error reports and new data sets were being forwarded to the creators of IBCAO, so that by the middle of 2002 a new and more definitive grid was ready to be placed into circulation. This was soon followed by the construction of a prototype shaded relief map that has been proposed as a successor to Sheet 5.17 of the General Bathymetric Chart of the Oceans (GEBCO)

A macroscopic scale model of bacterial flagellar bundling

Escherichia coli and other bacteria use rotating helical filaments to swim. Each cell typically has about four filaments, which bundle or disperse depending on the sense of motor rotation. To study the bundling process, we built a macroscopic scale model consisting of stepper-motor-driven polymer helices in a tank filled with a high-viscosity silicone oil. The Reynolds number, the ratio of viscous to elastic stresses, and the helix geometry of our experimental model approximately match the corresponding quantities of the full scale E. coli cells. We analyze digital video images of the rotating helices to show that the initial rate of bundling is proportional to the motor frequency and is independent of the characteristic relaxation time of the filament. We also determine which combinations of helix handedness and sense of motor rotation lead to bundling.Comment: 6 pages, 4 figures (3 in color). A supporting movie is published at the PNAS websit

Swimming Efficiency of Bacterium Escherichia Coli

We use in vivo measurements of swimming bacteria in an optical trap to determine fundamental properties of bacterial propulsion. In particular, we determine the propulsion matrix, which relates the angular velocity of the flagellum to the torques and forces propelling the bacterium. From the propulsion matrix dynamical properties such as forces, torques, swimming speed and power can be obtained from measurements of the angular velocity of the motor. We find significant heterogeneities among different individuals even though all bacteria started from a single colony. The propulsive efficiency, defined as the ratio of the propulsive power output to the rotary power input provided by the motors, is found to be 0.2%.Comment: 6 page

Hypsometry, Volume and Physiography of the Arctic Ocean and Their Paleoceanographic Implications

Recent analyses of the International Bathymetric Chart of the Arctic Ocean (IBCAO) grid model include: Hypsometry (the distribution of surface area at various depths); ocean volume distribution; and physiographic provinces [Jakobsson 2002; Jakobsson et al., in press]. The present paper summarizes the main results from these recent studies and expands on the paleoceanographic implications for the Arctic Ocean, which in this work is defined as the broad continental shelves of the Barents, Kara, Laptev, East Siberian and Chukchi Seas, the White Sea and the narrow continental shelves of the Beaufort Sea, the Arctic continental margins off the Canadian Arctic Archipelago and northern Greenland. This, the Worlds smallest ocean, is a virtually land-locked ocean that makes up merely 2.6 % of the area, and 1.0 % of the volume, of the entire World Ocean. The continental shelf area, from the coastline out to the shelf break, comprises as much as 52.9 % of the total area in the Arctic Ocean, which is significantly larger in comparison to the rest of the world oceans where the proportion of shelves, from the coastline out to the foot of the continental slope, only ranges between about 9.1 % and 17.7 %. In Jakobsson [2002], the seafloor area and water volume were calculated for different depths starting from the present sea level and progressing in increments of 10 m to a depth of 500 m, and in increments of 50 m from 550 m down to the deepest depth within each of the analyzed Arctic Ocean seas. Hypsometric curves expressed as simple histograms of the frequencies in different depth bins were presented, along with depth plotted against cumulative area for each of the analyzed seas. The derived hypsometric curves show that most of the Arctic Ocean shelf seas besides the Barents Sea, Beaufort Sea and the shelf off northern Greenland have a similar shape with the largest seafloor area between 0 and 50 m. The East Siberian and Laptev seas, in particular, show area distributions concentrated in this shallow depth range, and together with the Chukchi Sea they form a large flat shallow shelf province comprising as much as 22 Besides being the world’s smallest ocean with the by far largest shelf area in proportion to its size, the Arctic Ocean is unique in terms of its physiographic setting. The Fram Strait is the only real break in the barrier of vast continental shelves enclosing the Arctic Ocean. The second largest physiographic province after the continental shelves consists of ridges, which is in contrast to the rest of the World’s oceans where abyssal plains dominate. As much as 15.8 % of the area is underlain by ridges indicating the profound effect they have on ocean circulation

Arctic Ocean Physiography

The first order physiographic provinces of the Arctic Ocean has been defined using the recently updated International Bathymetric Chart of the Arctic Ocean (IBCAO) grid model as the main database and a semi-quantitative approach. The first step in our classification of physiographic provinces is an evaluation of seafloor gradients contained in a slope model that was derived from the IBCAO grid. The slope information reveals certain seafloor process-related features, which add to the bathymetric information. Using interactive 3D-visualization, the slope and bathymetric information were simultaneously analyzed and certain slope intervals of the Arctic Ocean seafloor were found to generally characterize major physiographic provinces. This information was used for the initial classification, although in certain locations gradual changes in bottom inclination made it difficult to detect transitions between some physiographic provinces, as for example, the transition between continental rise and slope, as well as between the rise and abyssal plain. In these cases some manual intervention was required guided by generated bathymetric profiles. The areas of the provinces we classified are individually calculated, and their morphologies are subsequently discussed in the context of the geologic evolution of the Arctic Ocean Basin as described in the published literature. In summary, our study: provides a physiographic classification of the Arctic Ocean sea floor according to the most up-to-date bathymetric model and addresses the geologic origin of the prominent features as well as provides areal computations of the defined first order physiographic provinces and of the most prominent second-order features

The Bacterial Chemotactic Response Reflects a Compromise Between Transient and Steady State Behavior

Swimming bacteria detect chemical gradients by performing temporal comparisons of recent measurements of chemical concentration. These comparisons are described quantitatively by the chemotactic response function, which we expect to optimize chemotactic behavioral performance. We identify two independent chemotactic performance criteria: in the short run, a favorable response function should move bacteria up chemoattractant gradients, while in the long run, bacteria should aggregate at peaks of chemoattractant concentration. Surprisingly, these two criteria conflict, so that when one performance criterion is most favorable, the other is unfavorable. Since both types of behavior are biologically relevant, we include both behaviors in a composite optimization that yields a response function that closely resembles experimental measurements. Our work suggests that the bacterial chemotactic response function can be derived from simple behavioral considerations, and sheds light on how the response function contributes to chemotactic performance.Comment: 19 pages, 5 figure

Independent- Jul. 24, 2007

https://neiudc.neiu.edu/independent/1369/thumbnail.jp

A Study of Cognitive Factors Which Contribute to Competence in the Biological Sciences

The aim of this study was to investigate factors which might contribute to competence in the biological sciences. Spatial skills are required for all biological studies which involve microscopy; form recognition, ability to recognise objects when their orientation is altered, ability to visualise from 2-D to 3-D, in a 3-D to 2-D direction. Ability to abstract information from a background which contains irrelevant material is required in microscopy, and also for morphological studies where tissues and organs are embedded in organisms. In all sciences, ability to abstract information, to reorganise it and then use it, is required, i.e. the skill of analysis. The biological sciences differ from the physical sciences in that there are a great number of anomalies at structural, functional and developmental levels. The ability to review a range of similarities and differences, in order to consider possible inter-relationships, would probably be enhanced by the ability to think divergently. The factors which were chosen were all of a cognitive nature -spatial ability, Field Independence, analytical skills and divergence. The following tests were constructed. Test A - Test of ability to visualise a 2-D section taken from a 3-D diagram. Test B - Test of ability to visualise a 3-D object when given appropriate 2-D sections. Test C - Test of ability to recognise a shape when its orientation was changed. Test D - Test of ability to find a number of solutions to a problem using the technique of grouping items into like categories (sets). This was a test for divergence; those who gave the greatest number of responses were judged to be more divergent than those who gave fewer answers. Test E - Test of ability to abstract relevant information from a distracting background. This was a dual purpose test, testing for the spatial skill of form recognition, and also for the cognitive style of Field Independence. Test F - Test of ability to abstract relevant information, to group characteristics which were similar but not identical, and to use it in a new situation. This was a test of analytical ability. After a trial run, the tests were amended and the following samples were taken. Primary 4/5 - primary school children aged 8-9 years Primary 7 - primary school children aged 10-11 years Secondary 2 - secondary school children aged 13-14 years Secondary 4 - pupils aged 15-16 studying Scottish 'O' Grade Biology Secondary 6 - pupils aged 17-18 studying Scottish 'H' Grade Biology or G.S.Y.S. in Biology. Undergraduate Biology students - in a first year University Glass of Biology I - most students were 18-19 years. Post-graduate biologists made up of teachers, lecturers and research students. Undergraduate students in the Arts and Divinity Faculties. Post-graduate non scientists made up of teachers, lecturers, social workers and others. All tests showed an age related trend, the young children having lower scores than the older pupils; the post-graduates performing better than the undergraduates. The different aspects of spatial ability did not develop at the same rate, the 3-D to 2-D skill taking the longest to develop. Analytical ability was poorly developed at the primary school level. There were more Field Independent individuals in the biology groups than in the non science groups. Post-graduate biologists showed the following characteristics -they had good spatial ability, good analytical skills, and tended to be Field Independent. The biology students, and the S. 6 (17-18 yrs) group also had these skills but to a lesser extent. The results of Test D for divergence were inconclusive so it was not possible to judge whether the biologists were more divergent than other groups. It might be argued that the study of biology improved the cognitive skills of spatial ability, Field Independence and analysis, but what was more likely was that those who did not have these potential skills were "siphoned off" during their school years. However, these skills would be used, extended and refined in biology courses. Those who did not have the above skills would be likely to select subjects more suited to a different cognitive repertoire, and would not opt for the sciences. Although the cognitive skills of spatial ability, analysis and Field Independence seemed to contribute success in the biological sciences, they probably play a similar role in the physical sciences

Continental Shelf Submissions: an Updated Record

To date, nine coastal states have presented a total of eight submissions for continental shelf extensions beyond their 200 nautical mile limits. This paper summarizes the scopes of those submissions and the stages they have attained in their examinations by the Commission on the Limits of the Continental Shelf. The paper also identifies the members of the three Commissions that have been elected since 1997, and of the seven subcommissions that have been established since 2001 for the purpose of reviewing individual submissions.Hoy, nueve Estados costeros han presentado un total de ochopropuestas sumisiones para la extensión de la plataformacontinental mas allá del límite de las 200 millas náuticas. Este artículo resume losaspectos de esas sumisiones y las etapas que han logrado en sus exámenes porla Comisión de Límites de la Plataforma Continental. El artículo también identificalos miembros de las tres Comisiones que han sido elegidos desde 1997, y de lassiete subcomisiones que han sido establecidas desde el 2001 con el propósito derevisar las sumisiones individuales.A ce jour, neuf Etats côtiers ont présenté huit soumissions au total pour des extensions du plateau continental au-delà de la limite des 200 milles marins. Le présent article résume la portée de ces soumissions et les stades atteints dans l'examen par la Commission sur les limites du plateau continental. Cet article identifie également les membres des trois Commissions qui ont été élus depuis 1997, et les sept sous-commissions établies depuis 2001 dans le but de passer en revue chaque soumission