Edges Of Ridges Research Articles

Lateral bone ridge expansion and internal tissue replacement for vertebral body growth in Pacific bluefin tuna Thunnus orientalis.

Vertebral growth is an essential developmental process to support the expansion of the vertebrate body. In teleosts, the lateral side of the vertebral bodies develops to form different structures among species in the late stages of vertebral growth, although lateral structures are not apparent in the early stages. Lateral structures are one of the structural features that determine the diversity of teleost vertebrae. However, explanations for the formation of lateral structures are conflicting because few reports have investigated the growth of teleost vertebral bodies. To clarify the growth process, we analyzed the morphological changes in the vertebral body of Pacific bluefin tuna Thunnus orientalis at different developmental stages using micro-computed tomography(CT) scans. The micro-CT scans showed that the vertebral centrum formed a plate-like ridge on the lateral side along the cranial-caudal direction and extended laterally with increasing thickness. Simultaneously, the proximal region of the lateral ridges became porous as the vertebrae grew to form bone marrow cavities. Furthermore, we used histological observations to describe the relationship between these morphological changes and osteoblast and osteoclast activities. Osteoblasts accumulated on the distal edges of the lateral ridges, whereas osteoclasts were distributed in the bone marrow cavities. These observations suggest that bone resorption occurs proximally to form bone marrow cavities in addition to bone synthesis at the edges of the lateral ridges. The bone marrow cavities were occupied by blood vessels, extracellular matrix, and adipocytes, and the internal tissue composition changed to increase the area of adipose tissue. Because the ratio of bone volume decreases in large vertebrae, bone formation and resorption are regulated to separate the external cortical and internal trabecular bones to support the vertebrae. This study is the first to report the formation of lateral structures and can be applied to similar lateral structures in the vertebrae of other teleost species.

Структурно-функциональные особенности ландшафтов с активным термокарстом в северной тайге Западной Сибири

<p>In the article, the main results of the study of dissolved greenhouse gases (CO<sub>2</sub>, CH<sub>4</sub>), dissolved organic carbon (DOC) and colloidal trace elements-metals in surface and soil waters of hollows, depressions, permafrost subsidences are considered. These waters were sampled in areas with active and stable permafrost thawing in Western Siberia. It is found that these zones of active termokarst are mainly located on the slopes and the bottoms of the upper reaches of rivers, which drain the interfluve. Active thawing of flat mound bogs leads to the appearance of numerous hollows, depressions and thermokarst subsidences, especially on the border between forest and fens. This is related to the additional heat input from the flowing water and causing the thawing deep permafrost on the edges of ridges occupied by the forest. Increase in specific conductivity (S.C.) in the smallest water bodies and supra-permafrost water is accompanied by a significant increase in concentrations of DOC, P, K, Cu, Zn, Mo and Ba. It has been found that small hollows and subsidence (< 10 – 100 м²) are characterized by much higher concentrations of DOC and CO<sub>2</sub> (p < 0.05) in comparison with large depressions and thermokarst water bodies. There is also a decrease of CH<sub>4</sub> concentration with an increase in the size of water bodies (p < 0.05), despite the fact that the data dispersion reaches 3 orders in small (<100 – 300 m²) water bodies of the where located zones active termokarst landscape, concentrations of DOC, CO2 and CH4 are significantly higher (p <0.05) than in the previously studied water bodies formed under conditions of a stable state of permafrost in areas of Nojabrsk and Khanymey. Waters of the active thawed of permafrost peat landscapes are usually rich in oxygen (saturation in the range of 30 ≤ O2 ≤ 105 %) and approximately 0.5 unit’s pH more acidic than areas with a stable state of permafrost. Many major and trace elements show a statistically significant decrease in concentration from very small water bodies (< 10 m²) to larger thermokarst waters. By the results of carried out research we can say that in the landscapes with active termokarst there will be direct mobilization of soil water in the hydrological network (rivers and lakes) with a minimal transformation of the water composition within the catchment area.</p>

Distribution of algal aggregates under summer sea ice in the Central Arctic.

The sea ice cover of the Arctic Ocean has changed dramatically in the last decades, and the resulting consequences for the sea-ice-associated ecosystem remain difficult to assess. Algal aggregates underneath sea ice are of great importance for the ice-associated ecosystem and the pelagic-benthic coupling. However, the frequency and distribution of their occurrence is not well quantified. During the IceArc expedition (ARK-27/3) of RV Polarstern in late summer 2012, we observed different types of algal aggregates floating underneath various ice types in the Central Arctic basins. We investigated the spatial distribution of ice algal aggregates and quantified their biomass, using under-ice image surveys obtained by an upward-looking camera on a remotely operated vehicle. On basin scale, filamentous aggregates of Melosira arctica are more frequently found in the inner part of the Central Arctic pack ice, while rounded aggregates mainly formed by pennate diatoms are found closer to the ice edge, under melting sea ice. On the scale of an ice floe, the distribution of algal aggregates in late summer is mainly regulated by the topography of the ice underside, with aggregates accumulating in dome-shaped structures and at the edges of pressure ridges. The average biomass of the aggregates from our sites and season was 0.1–6.0 mg C m−2. However, depending on the approach used, differences in orders of magnitude for biomass estimates may occur. This highlights the difficulties of upscaling observations and comparing results from surveys conducted using different methods or on different spatial scales.Electronic supplementary materialThe online version of this article (doi:10.1007/s00300-014-1634-3) contains supplementary material, which is available to authorized users.

Tracking basement cross-strike discontinuities in the Indian crust beneath the Himalayan orogen using gravity data – relationship to upper crustal faults

The Himalaya is the result of the on-going convergence and collision of India and Asia. The internal configuration and processes that govern the rise of the Himalayan Mountains and Tibetan Plateau are crucial to understand continental collision zones. However, knowledge of the prior configuration of the colliding plates is equally important, since inherited (pre-orogenic/basement) structures can undeniably influence the development of the orogenic architecture throughout the orogen's cycle of collision and eventual collapse. Three northeast-trending palaeotopographic ridges of faulted Precambrian Indian basement underlie the Ganga basin south of the Himalaya. Our paper illustrates a crustal-scale fault origin for these ridges and succeeds in determining how far north beneath the Himalayan system they extend and how they ultimately govern the location of upper crustal faults in southern Tibet. Spectrally filtered EGM2008 Bouguer gravity data and edges in its horizontal gradient at different source depths ('gravity worms') over northern Peninsular India, the Himalaya and southern Tibet reveal several continuous Himalayan cross-strike discontinuities interpreted to represent crustal faults. Gravity lineaments in Peninsular India coincide with edges of the Precambrian basement ridges and megakinks up to 100 km wide develop in foreland cover sequences between the interpreted basement faults. The interpreted basement faults project northward beneath the Himalayan system and southern Tibet. Our results suggest that several active Himalayan cross-strike faults, such as the ones related to many graben in southern Tibet, are rooted in the underplated Indian lower crust or step en echelon along interpreted basement faults. Our interpretation thus suggests that south Tibet graben are spatially related to deep-seated crustal-scale faults rooted in the underplated Indian crust. These major discontinuities partition the Himalayan range into distinct zones, and could ultimately contribute to lateral variability in tectonic evolution along the orogen's strike.

Evidence for current-controlled morphology along the western slope of Hatton Bank (Rockall Plateau, NE Atlantic Ocean)

A multibeam bathymetric and high- (airgun and sparker) to very high-resolution (Topas) seismic study of the western slope of Hatton Bank (NE Atlantic), located between 600 m and 2,000 m water depth, has revealed a highly variable range of current-controlled morphological features. Two major seabed areas can be distinguished: (1) a non-depositional area corresponding to the top of the bank and (2) a depositional area in which the Hatton Drift has developed. Both areas are characterised by distinct morphologies associated either with rock outcrops and rocky ridges or with smooth surfaces, slides and bedforms controlled mainly by bottom currents interacting with the topography of the bank. The water depth separating the morphological areas probably coincides with the boundary of the Labrador Sea Water and the Lower Deep Water. Morphological features identified in the study area include contourite channels (moats, furrows and scours), fields of sediment waves, edges of contourite deposits, ponded deposits, scarps, gullies, ridges, depressions, slides and slide scars. These morphological features do not necessarily reflect present-day conditions but may have been associated with past current events, consistent with earlier interpretations.

The surface microstructure controlled growth of organic nanofibres

A combination of top down fabrication of microstructured growth templates and bottom upgrowth of oriented organic nanofibres is demonstrated. At appropriate surface temperaturesblue light emitting para-hexaphenylene nanofibres are grown on gold coated siliconsubstrates, perpendicularly oriented to the edges of micron-sized ridges. These nanofibreshave well-defined maximum lengths of a few micrometres and typical heights and widths ofaround a hundred and a few hundred nanometres, respectively. Previously suchoriented growth has been reported solely on specific, single-crystalline growthsubstrates. The present finding opens up a route to direct growth of orientedorganic nanofibres on microstructured substrates that can act as device platforms.

MICROSTRUCTURE OF POLYPTERID SCALES (OSTEICHTHYES: ACTINOPTERYGII: POLYPTERIDAE) FROM THE UPPER CRETACEOUS BAHARIYA FORMATION, BAHARIYA OASIS, EGYPT

Histology of newly discovered ganoid scales from the lower Bahariya Formation, in the Bahariya Oasis of western Egypt, confirms the presence of polypterid osteichthyans in this early Cenomanian locality. These fossils, occurring in the ∼97 million-year-old lower Bahariya sequences, are among the earliest known polypterids. The Bahariya scales exhibit four tissues: ganoin, dentine, isopedine (elasmodin), and a basal plate of cellular bone, confirming their inclusion within the Polypteriformes. They have a discontinuous ganoin layer, present only as highly variable ridges and bosses. Dentine along the edges of the ganoin ridges appears to have undergone active remodeling, suggesting that the ganoin ridges represent the remnants of a continuous ganoin cover. Modern polypterids inhabit exclusively freshwater environments. Polypterids are not rare in the lower Bahariya Formation. Their presence in these coastal sediments suggests that freshwater habitats lay close to the site of deposition of this sequence during the early Cenomanian.

Inhomogeneous distribution of dislocations in a SiGe graded layer and its influence on surface morphology and misfit dislocations at the interface of strained Si∕Si0.8Ge0.2

To improve the quality of a strained Si layer on a SiGe virtual substrate, the distribution of dislocations in a graded SiGe layer is characterized using electron beam induced current (EBIC). A crosshatch pattern of dark and bright bands running along the two ⟨110⟩ directions is observed in an EBIC image taken with a 25-keV-electron beam at 80 K. These dark and bright EBIC bands are attributed, respectively, to high- and low-density dislocation regions in the graded SiGe layer, as is confirmed by transmission electron microscopy. The effects of such an inhomogeneous dislocation distribution on the surface morphology and the generation of misfit dislocations (MDs) at the interface of strained Si∕SiGe are investigated. Comparison between the EBIC image and an atomic force microscope image shows that the high-density dislocation regions are correlated with ridges on the surface topography. A chemical etching image shows that most of the MDs lie along the edges of surface ridges. Possible mechanisms of MD generation at the interface of the strained Si∕SiGe are proposed.

Thermoelastic stress in GaAs/AlGaAs quantum cascade lasers

We have determined the shear stress associated with the temperature gradient in quantum cascade lasers operated in continuous-wave mode. This information was obtained as a function of the electrical power using a combination of microprobe photoluminescence and anti-Stokes/Stokes Raman measurements in ridge-waveguide GaAs structures mounted epilayer down to the heat sink. At electrical power densities in the order of ∼5 kW/cm2, the strain in the cladding layers at the edges of the laser ridges reaches the critical value for the creation of misfit dislocations. Above 10–12 kW/cm2, extended defect formation and eventual device failure are observed.

The attachment and growth behavior of osteoblast-like cells on microtextured surfaces

In previous studies, we showed that the application of microgrooves on a surface can direct cellular morphology and the deposition of mineralized matrix of osteoblast-like cells (Biomaterials 20 (1999) 1293; Clin. Oral Impl Res. 11 (2000) 325). In this study, we evaluated the attachment and growth behavior of these cells, using scanning- and transmission electron microscopy (SEM/TEM). Smooth and microgrooved polystyrene substrates were made (groove depth 0.5–1.5 μm, groove- and ridge width 1–10 μm). On these substrates, osteoblast-like cells were cultured for periods up to 16 days. SEM showed that the cells, and their extensions, closely followed the surface on smooth and wider grooved (>5 μm) substrates. In contrast, narrow grooves (<2 μm) were bridged. After 16 days of incubation, the matrix showed extensive deposition of collagen fibrils, and the formation of calcified nodules. With TEM it was shown that on the smooth and wider grooved substrates, focal adhesions were spread throughout the surface. However, on narrow grooves focal adhesions were always positioned on the edges of surface ridges only. Apparently, most extracellular matrix (ECM) was produced by the cells that directly adhered to the substrate. Deposition of ECM was seen in the surface grooves, as well as in between the cell layers. On basis of the current study and previous experiments, we conclude that microgrooves are able to influence bone cell behavior by (1) determining the alignment of cells and cellular extensions, (2) altering the formation and placement of cell focal adhesions, and (3) altering ECM production. Therefore, microgrooved surfaces seem interesting to be applied on bone-anchored implants.

Functional significance of ontogenetic gradients in the enamel ridge pattern of the upper cheek dentition of the miocene hipparionin horseCormohipparion occidentale (Equidae, Perissodactyla)

The cheek tooth dentition of hipparionine horses functions as a shearing system, masticating food in a single phase occlusal power stroke. The edges of enamel ridges, which are exposed on the occlusal surface by means of food abrasion act as shearing blades. In order to discern the function of enamel ridges, an algorithm is introduced which reduces occlusal enamel ridge patterns to their functional residual in respect to the function as a shearing system. A further algorithm discriminates actively functioning (leading) enamel edges from passive functioning (trailing) edges. The residuals of functional enamel edges are investigated in respect to their alignment in relation to the chewing direction. A cheek tooth dentiion of the Miocene hypsodont equidCormohipparion occidentale is investigated in respect to wear related ontogenetic changes in functional enamel edge alignment using a set of 8 sections per tooth roughly representing hypothetical occlusal surfaces in different individual ages.

Surface diffusion limited nucleation of Ge dots on the Si(001) surface

The formation of Ge islands during MBE growth is a spontaneous process and these islands, i.e. dots, are usually randomly arranged. In order to implement these nanoscaled islands into device applications, ordering of epitaxial dots is a crucial step. We report a study on the MBE growth of Ge islands on Si(001) substrates, containing 〈110〉-oriented square and long stripe type patterns defined by anisotropic wet etching of Si, in order to provide more understanding of how surface diffusion of Ge atoms would influence the formation of Ge islands on various types of surfaces. It has been found that there were preferential nucleation sites for Ge islands along the bottom edges of the Si ridges. The Ge islands at the edge positions were larger than those formed on the free surface and they could be regularly spaced. Due to the consumption of Ge at the bottom edges of ridge patterns, the density of Ge dots on the free surface varied between ≈3×10 8 and ≈1×10 9 cm −2 when changing the spatial separation between two adjacent Si ridges (2–100 μm). A Ge mean diffusion length of ≈7.5 μm has been determined for Ge growth at 700 °C.

Growth behavior of fibroblasts on microgrooved polystyrene

We investigated the contact guidance phenomenon of rat dermal fibroblasts (RDF) on microgrooved polystyrene substrates. Grooves were 1 μm deep, and between 1 and 10 μm wide. Light microscopy and digital image analysis (DIA) showed that RDF were oriented on all microgrooved substrates. Scanning electron microscopy showed that RDF cultured on 1 or 2 μm wide grooves were positioned on top of the ridges. On the wider 5 and 10 μm grooves, the cells were able to descend into the grooves. In confocal laser scanning microscopy, focal adhesions were lying in the same direction as the actin filament where they attached to. DIA confirmed an orientational behavior of focal adhesions and actin filaments on microgrooves. There were no differences in the measured orientation between the different grooves. Besides, no obvious preference was found for focal adhesions to lie along edges of the surface ridges. Transmission electron microscopy showed that focal adhesions were able to bend along the edges of ridges. On the basis of our observations, we suggest that the breakdown and formation of fibrous cellular components, especially in the filopodium, is influenced by the microgrooves. The microgrooves create a pattern of mechanical stress, which influences cell spreading and cause the cell to be aligned with surface microgrooves.

Glacial Topography of the Mountains of North-eastern Korea

Concerning the glacial topography of Korea, no accurate knowle, dge was hitherto available, excepting Supan's doubtful accounts. Having been informed by Prof. Takenaka, a well-known alpinist in Korea, of the presence of such a topography in the KanbO mountains, I wade a trip to that country in the summer of 1936 to search for traces of former glaciation in the north-eastern part of the said coun-try, and obtained the following information regarding the mountains of Kanbo, Hakuto, and Minami-hotai: 1. Kanbo mountains. In this mountain range, situated in the north-eastern edge of the Kaima plateau, in a NNE-SSW direction for a distance of nearly 60km, its highest peak is Kambo-ho, which is 2541m high. Tt, e mountains are chiefly composed of granite-gneiss, and the wide surfaces of small relief on the summit at altitudes of 2300-2400 are believed to be the remnants of an upwarped peneplain. As far as my observations go, of the cirqes, which are the most striking topography of that kind, there are fourteen in all, being markedly developed on the eastern and northern faces of the mountains. Of cirques, the most prominent are those on the eastern side of the ridge stretching from Kitasetsurei (2442m) via Kodaiho (2471m) to Nishikanbo (2432m). They are large, being 700m wide and over 800m long. The cirque walls are very high, . those that exceed 200m having steep inclinations, in strong contrast to the upper edges of the wide level ridges. The three cirques that are developed on the northern side of Kitasetsurei are almost as large as those just mentioned, although their inclinations are not so steep. The bottoms of all the cirques are filled with large quantities of morainic blocks, gravels, and sands. Some of the morainic hills exceed 30m in height. The morains that consist of granite-gneiss are irregular in shape and rugged on their surfaces, whereas those composed of hard sandstone are typically subangular in shape, well-facetted and distinctly striated. The floors of the cirques are from about 1900 to 2150m above sea-level, but whether they correspond to the height of the snow-line or not is unknown at present. Besides the cirques, a glacial trough, which originated from a cirque situated north of Nishi-Kanbo, descends in a NNE direction for a distance of 3km to about an altitude of 1500m. This is confluenced by the three tributaries of shorter glacial troughs continuing from the cirques developed on the eastern face of a ridge that stretches from Kitasetsurei to Nishi-Kanbo. The cirques are prominently distributed on the eastern side of the ridges, with but a few on the northern, and none on the western and southern ridges, which f act clearly suggests influence of the westerly winter monsoons. Because of the comparatively slight weathering during post-glacial time, the glacial topography is well preserved in most all the ridges, but the cirques on the eastern chain, running between Kitakanbo and Minami-kanbo, seem to have been destroyed by the active headward erosion of the downstream. II. Mount Hakuto. Mount Hakuto, situated on the frontier between Manchouko and Korea, is the main peak of the Hakuto volcanic chain. Its highest summit, Taishoho, attains to a height of 2750m above sea-level. Geologically, Mount Hakuto is a composite volcanoes of tholoide, built up of various alkaline rocks of tra chytic type that erupted during the end of the Tertiary. After the formation of the caldera lake Tenchi (about 4km in longer diameter), basic lava flowed out in the vicinity during the Quarternary period, burying Mount Hakuto on its flank, the summit alone being free from repeated accumulations of the lava flows. The explosions that occurred quite recently have made the topographical microf arms quite indistinct as the result of thick accumulations of pumice exceeding 10m in thickness. The inner side of the caldera wall of Mt.