An Unusual Case of Stream Piracy

An unusual case of stream piracy took place in the recent past through the Franklin Bluffs on the Arctic Coastal Plain of Alaska. The Sagavanirktok River and Hawk Creek occupied opposite positions on the sides of a ridge, with the result of a rapid lowering of the divide between them. Loss of cementation (by thaw) of the gravels in the formation separating them continued until the higher flowing Hawk Creek burst through the ice-free gravels of the ridge to join the Sagavanirktok River about one-half mile upstream from its former junction

Alluvial Fan Development at Franklin Bluffs, Alaska

This paper is concerned with the developmental history of alluvial fans forming in a tundra climate. The study was made at Franklin Bluffs, Alaska (69° 48\u27 - 70° 00\u27 N, 148° 40\u27 W), during the summer of 1961. The area is an ideal place in which to study the developmental history of alluvial fans in that so many stages are present in a relatively small area. A theoretical sequence of fan development was set up, illustrated by examples from the Franklin Bluffs, which show how certain characteristics of an alluvial fan, forming in a tundra climate, change as the sequence advances. The sequence was designated A, B, C, D, and E, where A is the youngest, near talus cone stage, and E is the oldest, near graded stage. Certain characteristics were found to constitute a continuum of changes in the sequence. The two most continuously changing factors are the difference in slope, between that of the drainage area and that of the fan, and the relative size of each fan -vs- drainage area. Also, in the progress of the sequence, the intensity of mass wasting decreases. Related to the type and intensity of mass-wasting and the amount and size distribution of surficial rock material and the amount and type of vegetation. The climax of the sequence is characterized by the approach to a well vegetated graded stage on which a permanent channel forms if sufficiently continuous discharge is present

Tundra Relief Features near Point Barrow, Alaska

Topography of this area results from erosion and mass wasting of a permafrost terrain, low temperature processes such as thermal expansion and contraction of frozen ground, surface uplift caused by accumulation of, and subsistence resulting from thaw of ground ice. High- and low-centered polygons, ice-wedge troughs, ice-core mounds and thaw basins are features in this region; genetic relations between these are discussed.Traits de relief de la toundra près de Point Barrow, Alaska. La distribution des traits mineurs du relief de la toundra démontre que la topographie joue un rôle majeur dans leur développement. Dans de grandes zones de relief très faible, l'expression locale dépasse souvent la portée régionale. Abstraction faite du relief initial, les plus grandes déviations de la surface plane dans la région de Barrow sont liées à la croissance ou à la fonte de la glace dans le sol. Ce qui donne des traits comme les polygones à centre soulevé ou en creux, les fentes de coins de glace, les monticules à noyau de glace et des cuvettes de fonte de toutes dimensions. On a pu déterminer la genèse de la plupart de ces traits. Cependant, on a mis en doute la formation des cuvettes par la fonte. La cueillette et l'analyse de spécimens de sol gelé ont permis de déterminer leur teneur relative en glace. Ces valeurs extrapolées ont démontré que même les plus grandes cuvettes peuvent être d'origine thermokarstique

Motor responses in amblyopia and anomalous retinal correspondence

Motor responses in amblyopia and anomalous retinal correspondenc

Elucidating the regulation of complex signalling systems in plant cells

The pollen tube represents a model system for the study of tip growth, and the root provides a valuable system to study gene and signalling networks in plants. In the present article, using the two systems as examples, we discuss how to elucidate the regulation of complex signalling systems in plant cells. First, we discuss how hormones and related genes in plant root development form a complex interacting network, and their activities are interdependent. Therefore their roles in root development must be analysed as an integrated system, and elucidation of the regulation of each component requires the adaptation of a novel modelling methodology: regulation analysis. Secondly, hydrodynamics, cell wall and ion dynamics are all important properties that regulate plant cell growth. We discuss how regulation analysis can be applied to study the regulation of hydrodynamics, cell wall and ion dynamics, using pollen tube growth as a model system. Finally, we discuss future prospects for elucidating the regulation of complex signalling systems in plant cells

Ground Patterns as Keys to Photointerpretation of Arctic Terrain

Data based on field observations made during the summers of 1955-61 substantiate the belief that angle of slope is the most significant factor in determining the type of ground pattern which regionally or locally features arctic terrain. The factors of influence in any arctic terrain ground pattern are texture of regolith, type and thickness of vegetation mat, amount of surface and subsurface water, thickness of active layer, and angle of slope of the ground surface. The angle of slope and texture of regolith determine surface and subsurface drainage to a large extent, and thus control the water loss from the area. The amount of water in the ground, in turn, plays a large role in determining the type and amount of vegetation that can grow in the area and, hence, the thickness of the vegetation mat. The vegetation mat, in turn, pretty well determines the thickness of the active layer. It is most thick (deep) where the mat is very thin, or absent. It was determined that equidimensional ground patterns, circular frost scars, hummocks, ice-wedge polygons, and sorted stone nets develop on slopes of less than two degrees. With increase in slope to four degrees, these patterns become elongated, but not aligned nor continuous, i.e.-not stripes. Further increase in slope to six degrees is featured by such linear features as stripes (both sorted and non-sorted), and by development of steps. Steps become much more pronounced on steeper slopes, and solifluction lobes characterize slopes in excess of eight degrees. Some changes in slope are very common and very local, so that a regional pattern peculiar to a slope of two to four degrees will be modified by a pattern of the locally developed steeper slope. Once one knows the significance of the different types of ground patterns, he can do an excellent job of determining terrain conditions of an unknown area from good air photos of that area

Connexin 43 as a biological marker of ischaemia in occlusive arterial disease of the lower limb

Diabetes mellitus is a worldwide health issue. It is a major and growing cause of morbidity and mortality. Rates of end-organ damage are increasing proportionately, as are the associated personal, societal and economic costs. Diabetic foot ulceration is responsible for a significant proportion of this. The development of diabetic foot ulceration is complex with multiple injurious processes potentially affecting a foot at any time. Defining the significance of ischaemia as a consequence of peripheral arterial occlusive disease can be difficult and identifying which patients may benefit from revascularisation in terms of reversing of the natural history of the disease process remains poorly understood. The utility of the University of Texas classification to identify patients at highest risk of major adverse clinical events has been explored from 971 ulcer episodes affecting 515 limbs (388 patients). Peripheral arterial occlusive disease was identified in 44.6%. These patients had a significantly higher risk of major amputation than patients without peripheral arterial occlusive disease (13.5 versus 4%). University of Texas scoring would appear to robustly identify patients at highest risk of major adverse clinical events. The potential usefulness of Connexin 43 and its phosphorylated isoform Connexin 43(Serine368) as biological markers of ischaemia in skin have been explored. Immunohistochemistry provided qualitative data demonstrating up regulation of Connexin 43(Serine368) in skin biopsies from ischaemic feet – this is a novel finding. Connexin 43 (Serine368) was not identified in any of the controls nor in proximal skin biopsies of patients with peripheral arterial occlusive disease. Connexin 43 expression did not appear to be modified. When human fibroblasts and keratinocytes were subjected to hypoxic conditions (1% oxygen/4% carbon dioxide/nitrogen) in vitro, both Connexin 43 and Connexin 43(Serine368) were up regulated with protein expression peaking between 12 to 24 and 6 to 12 hours respectively. Peptidoglycan challenge appeared to up-regulate the expression of Connexin 43 protein, but did not influence the expression of Connexin 43(Serine368). These data suggest that Connexin 43(Serine 368) may have potential utility as a biological marker of ischaemia in human ski

The Varied Character of the Des Moines River Valley in Central Iowa

The drainage system on the Des Moines River is quite varied between Humboldt and Des Moines. The variation in drainage characters is highlighted on a map prepared from aerial photographs and topographic sheets. The northern part of this area is associated with the Mankato drift sheet and is characterized by poorly developed, non-integrated drainage. The central part of the drainage system in Boone County flows across the Cary ground moraine. In this area the tributaries are short, intermittent, and deep, and appear as gullies and washes. Just south of Des Moines, the drainage makes another sharp change, and in this area is associated with the Kansan drift. It is well integrated and featured by a relatively small number of far-reaching primary tributaries. It seems to be more than coincidental that the change in character of the drainage is so closely associated with the relative ages of the drift sheets comprising the drift plain