Network Of Ridges Research Articles

New Insights into Morphological and Biological Features of Capillaria aerophila (Trichocephalida, Trichuridae)

Capillaria aerophila is a trichuroid nematode affecting the respiratory system of dogs, cats, wild carnivores and, occasionally, humans. Animals become infected by ingesting larvated eggs or earthworms, which act as facultative intermediate hosts. The aim of this work is to present new insights into morphological and biological features of this neglected lungworm. Typical features of C. aerophila eggs, differentiating them from those of most known trichuroid whipworms (i.e. size, asymmetry of bipolar plugs and a wall with a network of anastomosing ridges), were detected upon light and scanning electron microscopy. Eggs of C. aerophila were used for in vitro development. Light microscopy showed typical features of C. aerophila eggs: size, asymmetry of bipolar plugs and a wall with a network of anastomosing ridges. All these features were confirmed upon SEM, in that C. aerophila eggs showed an outer densely striated and net-like shell. Eggs of T. vulpis, used for a comparative analysis, were bigger than those of C. aerophila and showed a thick and smooth wall at both light and scanning electron microscopy. Eggs started to develop after 35 days from shedding and mobile larvae were observed in the eggs after two months. The results of this study provide key information on the biological cycle of C. aerophila and present key morphological characters for the identification of eggs in faeces.

Ceramic-based microelectrode arrays: Recording surface characteristics and topographical analysis

Amperometric measurements using microelectrode arrays (MEAs) provide spatially and temporally resolved measures of neuromolecules in the central nervous system of rats, mice and non-human primates. Multi-site MEAs can be mass fabricated on ceramic (Al 2O 3) substrate using photolithographic methods, imparting a high level of precision and reproducibility in a rigid but durable recording device. Although the functional capabilities of MEAs have been previously documented for both anesthetized and freely moving paradigms, the performance enabling intrinsic physical properties of the MEA device have not heretofore been presented. In these studies, spectral analysis confirmed that the MEA recording sites were primarily composed of elemental platinum (Pt°). In keeping with the precision of the photolithographic process, scanning electron microscopy revealed that the Pt recording sites have unique microwell geometries post-fabrication. Atomic force microscopy demonstrated that the recording surfaces have nanoscale irregularities in the form of elevations and depressions, which contribute to increased current per unit area that exceeds previously reported microelectrode designs. The ceramic substrate on the back face of the MEA was characterized by low nanoscale texture and the ceramic sides consisted of an extended network of ridges and cavities. Thus, individual recording sites have a unique Pt° composition and surface profile that has not been previously observed for Pt-based microelectrodes. These features likely impact the physical chemistry of the device, which may influence adhesion of biological molecules and tissue as well as electrochemical recording performance post-implantation. This study is a necessary step towards understanding and extending the performance abilities of MEAs in vivo.

Giant melanoacanthoma mimicking malignant melanoma

Melanoacanthoma denotes a rare variant of pigmented seborrheic keratosis. A 65-year-old male farmer had pigmented, verrucous, itchy, highly painful, progressively growing irregularly oval plaque on left side of lower back for the past five years. The indurated lesion, measuring maximum diameter 10 cm × 5 cm, had no discharge, bleeding, ulceration, or associated lymphadenopathy. Dermoscopy showed regular pigmentary network and cribiform pattern of ridges without any feature of malignant melanoma. Histopathology showed well-defined islands of basaloid cells interspersed with large and richly dendritic melanocytes. The lesion was totally excised followed by skin grafting. Our patient was unique in its massive size and clinical resemblance with malignant melanoma. The diagnosis was confirmed by dermoscopy and skin biopsy.

Nanomanipulation of ridges in few-layer epitaxial graphene grown on the carbon face of 4H-SiC

The atomic force microscope (AFM) is used to study the morphology of graphene grown on 4H-SiC. A mesh-like network of ridges with high curvature is revealed that bound atomically flat, tile-like facets of few-layer graphene (FLG). To further study the structural properties of the ridge network, nanomanipulation experiments are performed using an AFM tip to deform the ridges in both the vertical and lateral directions. From these experiments, evidence is obtained that the ridges can be displaced in both the vertical and lateral directions. In some instances, ridges are found to return to their original shape after deformation. Cross-section transmission electron microscopy (TEM) studies show that the ridges are formed by the delamination of FLG from the SiC substrate.

Direct observation of the temporal and spatial dynamics during crumpling

Crumpling occurs when a thin deformable sheet is crushed under an external load or grows within a confining geometry. Crumpled sheets have large resistance to compression and their elastic energy is focused into a complex network of localized structures. Different aspects of crumpling have been studied theoretically, experimentally and numerically. However, very little is known about the dynamic evolution of three-dimensional spatial configurations of crumpling sheets. Here we present direct measurements of the configurations of a fully elastic sheet evolving during the dynamic process of crumpling under isotropic confinement. We observe the formation of a network of ridges and vertices into which the energy is localized. The network is dynamic. Its evolution involves movements of ridges and vertices. Although the characteristics of ridges agree with theoretical predictions, the measured accumulation of elastic energy within the entire sheet is considerably slower than predicted. This could be a result of the observed network rearrangement during crumpling.

Strain-Induced Segmentation of Magnesian Calcite Thin Films Growing on a Calcite Substrate

In crystal growth of mineral species or different compositional members of a solid solution on one another, the degree of lattice mismatch at their interface affects the growth pattern of the precipitating mineral phase. Fast layer-by-layer growth of magnesian calcite on pure calcite (1014) substrates has been observed at Mg 2+ /Ca 2+ ratios of 2-7 using in situ atomic force microscopy. Under solution conditions of calcite saturation states starting from Ω ≈ 33, depending on Mg 2+ /Ca 2+ ratios and carbonate content, bulging in the epitaxial magnesian calcite thin film led to the formation of networks of ridges along the [441], [481], and [421] directions. Eventually, spreading of monolayers stopped at the ridges and formed stationary multilayer steps, resulting in separate and individually growing crystal segments. Molecular dynamics computational modeling suggests that relaxation of strain energy, caused by the interfacial lattice mismatch between pure calcite and the isostructural magnesium-containing phase with smaller lattice constants, leads to a semicoherent interface and disordered linear zones cutting through the thin film. As a consequence, the surface bulges up in a way similar to our laboratory observations. This strain-induced segmentation produces aggregates of aligned microcrystals and increase knowledge of the behavior of strained thin films in general.

Formation of pyramid-like nanostructures in MBE-grown Si films on Si(001)

The growth of Si homoepitaxial layers on Si(001) substrates by molecular beam epitaxy is analyzed for a set of growth conditions in which diverse nanometer-scale features develop. Using Si substrates prepared by exposure to HF vapor and annealing in ultra-high vacuum, a rich variety of surface morphologies is found for different deposited layer thicknesses and substrate temperatures in a reproducible way, showing a critical dependence on both. Arrays of 3D islands (truncated pyramids), percolated ridge networks, and square pit (inverted pyramid) distributions are observed. We analyze the obtained arrangements and find remarkable similarities to other semiconductor though heteroepitaxial systems. The nanoscale entities (islands or pits) display certain self assembly and ordering, concerning size, shape, and spacing. Film growth sequence follows the ‘islands–coalescence–2D growth’ pathway, eventually leading to optimum flat morphologies for high enough thickness and temperature.

Influence of pore water chemistry on silica diagenesis: evidence from the interaction of diagenetic reaction zones with polygonal fault systems

Abstract: Three-dimensional seismic data from the NE Atlantic margin have revealed opal-A to opal-CT reaction zones hosted in Oligo-Pliocene strata as bright reflection events that cross-cut stratigraphic reflections. In some areas, the topographic relief at the top of the reaction zone has a remarkable geometry comprising roughly circular flattish regions, spaced 1–3 km apart, separated by networks of steep-sided troughs or ridges with a relief of up to 200 m. Here we show that these topographic structures formed around the upper tips of polygonal faults, and that remnants exist at deeper stratigraphic levels below the opal-A to opal-CT cross-cutting reflection. Furthermore, we deduce that the chemistry of formation water expelled transiently through the polygonal faults must have played a key role in their formation. Within silica-bearing successions, the transformation of opal-A to opal-CT is followed by the transformation of opal-CT to quartz at greater depth. The opal-CT to quartz transformation releases magnesium, which is known to promote opal-A to opal-CT transformation at lower temperatures. Consequently, we suggest that when the opal-A to opal-CT reaction zone nears the top of the polygonal fault system, it advances more rapidly through strata flushed by pore water that is richer in magnesium.

AFM study of ridges in few-layer epitaxial graphene grown on the carbon-face of 4H–SiC[formula omitted

A characterization of the graphitic overlayer that forms on 4H–SiC(0001¯) substrates heated for ten minutes to temperatures T>1350°C under vacuum conditions has been performed. X-ray photoelectron spectroscopy of the C-face reveals the presence of graphitic carbon with a thickness that increases with growth temperature. Parallel atomic force microscope (AFM) studies find a mesh-like network of ridges with high curvature that bound atomically flat, tile-like facets of few-layer graphene (FLG). By imaging the network that develops on FLG, it is possible to map out the regions where the elastic energy is concentrated.

Comparative morphology of the eggs in some Panorpidae (Mecoptera) and their systematic implication

The egg ultrastructure of 12 species in three genera of Panorpidae: Panorpa Linnaeus, Neopanorpa Weele and Sinopanorpa Cai & Hua, was examined using scanning electron microscopy. This is the first time the egg characters have been studied in detail for this family. The results show that egg morphology can be utilised for panorpid taxonomy both at the generic and specific levels. In the species investigated, the egg chorion is covered with a network of extrachorion. Several micropyles were visible on the anterior pole of the eggs after the extrachorion was removed. Neopanorpa eggs differ from the other two genera by neighbouring ridges of exochorion, which are separate and independent. The eggs of Sinopanorpa and Panorpa have only one fused ridge between every two adjoining polygonal cells. The eggs of Sinopanorpa have a network of ridges with even top edges, the granules within the cells being small and uniform. However, the eggs in the nine species of Panorpa are very diverse in morphology, reaffirming the heterogeneity and paraphyly of Panorpa, which may need further systematic analyses.

Oxidation resistance of Pt-modified γ/γ′ Ni-Al at 1150 °C

Nickel aluminide coatings are used to protect the surfaces of turbine engine hot-stage components. Increasing service temperatures are driving the need for improved performance coatings, which grow and retain thin, protective alumina scales. This paper describes the oxidation resistance of platinum-modified, two-phase (γ/γ′) Ni-22Al materials at 1150 °C in air. Under isothermal conditions, a composition of Ni-22Al-30Pt (at.%) oxidises with the same parabolic rate constant as β-NiAl. The addition of hafnium reduces the rate by an order of magnitude. The protective oxide formed is in all cases α-Al 2O 3. Focused ion beam (FIB) milling was used to examine the very thin scales. In 100 h of reaction, a hafnium-free Ni-Al-Pt material grew a roughly uniform scale 4–5 µm thick, decorated with numerous oxide whiskers. At the same time, a coating containing 0.5 at.% Hf grew a very thin (< 0.5 µm) oxide over which developed a network of ridges about 1 µm high. The effects of hafnium are discussed in terms of oxide transport properties. Possible explanations for the beneficial effects of platinum are also considered.

Cell contacts in the mouse mammary gland

The nature and distribution of cell contacts have been examined in thin sections and freeze-fracture replicas of mammary gland samples from female C3H/Crgl mice at stages from birth through pregnancy, lactation, and postweaning involution. Epithelial cells of major mammary ducts at all stages examined are linked at their luminal borders by junctional complexes consisting of tight junctions, variable intermediate junctions, occasional small gap junctions, and one or more series of desmosomes. Scattered desmosomes and gap junctions link ductal epithelial and myoepithelial cells in all combinations; hemidesmosomes attach myoepithelial cells to the basal lamina. Freeze-fracture replicas confirm the erratic distribution of gap junctions and reveal a loose, irregular network of ridges comprising the continuous tight-junctional belts. Alveoli develop early in gestation and initially resemble ducts. Later, as alveoli and small ducts become actively secretory, they lose all desmosomes and most intermediate junctions, whereas tight and gap junctions persist, The tight-junctional network becomes compact and orderly, its undulating ridges oriented predominantly parallel to the luminal surface. It is suggested that these changes in junctional morphology, occurring in secretory cells around parturition, may" be related to the greatly enhanced rate of movement of milk precursors and products tbrough the lactating epithelium, or to the profound and recurrent changes in shape of secretory cells that occur in relation to myoepithelial cell contraction, or to both.

Structural peculiarities of carbon nanolayers prepared by deposition from a gaseous phase on Ni

The surface structure and the mechanical and electrical properties of graphite nanolayers (1–2 nm thick) obtained by the carbon deposition from a gaseous phase on a Ni surface were studied using atomic-force microscopy (AFM). The surface of the nanolayers contains a dense network of line ridges with transverse sizes of several nanometers to several tens of nanometers and with the length of linear segments up to 1–2 μm. The AFM studies permit the conclusion that the observed ridges are mainly formed from carbon nanotubes or nanofilaments. They differ from planar areas of the graphite layer by substantially higher local electric conductivity in the contact with an AFM probe. The formation of ridges on certain portions of the surface may be due to thermal deformation wrinkles of graphite nanolayers that arise on cooling to room temperature.

Two new species of Perichaena (Myxomycetes) from arid areas of Russia and Kazakhstan

Two new myxomycete species from dry steppe and desert communities of the Caspian Lowland (Russia) and central Kazakhstan are described and illustrated. They are placed tentatively within genus Perichaena, which does include species with a reduced capillitium and single-layered peridium. Both species were found repeatedly in moist chamber cultures; P. heterospinispora appeared on leaf litter and twigs, whereas P. polygonospora occurred on leaf litter and weathered dung of rodents. Both species have spore ornamentation that is unique for members of genera Licea and Perichaena. The spore ornamentation of the first species includes scattered large, pyramid-like spines 0.9–1.2 μ m high that sometimes have enlarged ends. Among these spines the spore surface is covered by evenly and densely distributed warts that are visible only by SEM. The second species is characterized by angular spores with a coarse network of rounded ridges. The areas among these ridges bear scattered composite warts 0.3–0.5 μ m high that sometimes coalesce to form clusters but more often are distributed evenly and densely and are visible only by SEM. The stability of the taxonomic characters of both species was confirmed by several collections from different regions obtained in 2 y. The morphology of the fructifications of the two myxomycetes was examined with both scanning electron and light microscopy, and micrographs of all relevant features are presented.

Ultrastructure and histochemistry of seeds of Colophospermum mopane during imbibition

An Environmental Scanning Electron Microscope (ESEM) was used to study the interaction between water and the seed surface of Colophospermum mopane during imbibition. A network of vein-like ridges that is caused by overlapping, compressed epidermal cells, traverses the dry seed surface. The areas where the epidermal cells overlap are characterized by a series of fine grooves. Temperature and pressure parameters in the specimen chamber were adjusted to obtain a relative humidity (RH) of 100%. Water precipitated onto the seed surface and a series of micrographs were taken over a period of approximately 8 h to capture the structural changes taking place. The entire seed surface is eventually covered with a thin, smooth mucilaginous layer as the outermost seed surface reacts with water. During imbibition, mucilage is also extruded from the epidermal grooves. Based on morphology and histochemistry, three different types of mucilage were identified in mopane seeds. Transmission Electron Microscopy (TEM) revealed that the inner cell wall surfaces of the seed coat and aril cells were lined with a thin mucilaginous layer that appeared to play a significant role during the unfolding and expansion of the compressed aril and seed coat cells.

The origin and glaciodynamic significance of sandstone ridge networks from the Hirnantian glaciation of the Djado Basin (Niger)

AbstractThe Djado Basin (Niger) was located beneath the inner part of the Late Ordovician ice sheet. The Felar‐Felar Formation consists mainly of glaciomarine deposits, associated with the major ice sheet recession within the glaciation, and is bounded by two glacial unconformities. Structures corresponding to sandstone ridges are found within the Felar‐Felar Formation. Sandstone ridges are several metres high, about 10 m wide and hundreds of metres long. These structures are organized in extensive anastomosed to sub‐polygonal networks. The association of sandstone ridge networks with the later glacial unconformity and with other glacial evidence suggests sub‐glacial conditions for their origin. Sandstone ridge sedimentological characteristics indicate that sandstone ridges result from the scouring of the Felar‐Felar Formation by sub‐glacial, turbulent and pressurized meltwater; then sub‐glacial cavities were infilled with sand derived from glacial abrasion. Sandstone ridge networks are comparable with tunnel channels and document unusual drainage structures of the inner part of the palaeo‐ice sheet.

Hf–Nd evidence for the origin and distribution of mantle domains in the SW Pacific

Pb isotope systematics have already been used successfully to demonstrate that the lavas of the arc-basin terrains of the SW Pacific are derived from two mantle domains, one of Pacific-like character and the other of Indian-like character. However, the mobility of Pb during subduction and alteration has mainly restricted the fingerprinting of domains to fresh lavas of MORB composition. We demonstrate that the less alteration-sensitive Hf–Nd isotope projection also discriminates successfully between ‘Pacific’ and ‘Indian’ domains, and thus enables us to extend mantle domain fingerprinting to the back-arc basin basalts and boninites of the Lau and North Fiji Basins and the volcanic arc lavas of the Kermadec, Tonga and Vanuatu arcs. Fingerprinting is facilitated by the observation that the Hf isotope ratio is independent of subduction-input parameters, indicating that Hf has been essentially conservative during the subduction process. Subducted Nd has been added to the mantle source, but subtracting this numerically using the magnitude of negative Hf anomalies filters out the subduction effect. The data show that the ‘Indian’ domain provides the source for magmas erupted at ridges, and arcs near these ridges, that have propagated southwards following the 12 Ma collision of the Ontong-Java Plateau with the Vitiaz Trench. This indicates that the ‘Indian’ domain is actually derived from SOPITA mantle (South Pacific Isotopic and Thermal Anomaly) — mantle modified by the Samoa and other plumes outboard of the trench which only entered the SW Pacific arc-basin system after the Ontong-Java Plateau collision removed the slab barrier at < 12 Ma. In the west, mantle flows beneath the network of south-propagating ridges in the North Fiji and NW Lau Basins, undergoing progressive depletion until the final loss of plume components produces an N-MORB mantle (Indian MORB Mantle) composition in the south North Fiji Basin and Central Lau Spreading Centre. In the east, newly-depleted Samoan plume mantle provides the source for the boninites and depleted arc tholeiites of the northern Tonga arc.

Characterisation of initial atmospheric corrosion carbon steels by field exposure and laboratory simulation

The early stages of the evolution of atmospheric corrosion of carbon steels exposed in both a laboratory simulated and a natural atmosphere environment in Shenyang have been observed by in situ scanning electron microscopy. In the case of laboratory cyclic wet–dry tests, even though the chloride content level is very low, filiform corrosion is initiated in the early stage. The filiform corrosion grows in random directions, forming a network of ridges. White nodules nucleate and grow on the ridges during continued corrosion and eventually connect with each other to form the initial corrosion scale. Pits were also found on the surface beneath corrosion products. In the case of a natural atmospheric environment, both filiform corrosion and other localized corrosion, such as pitting and inter-granular attack take place in the initial stage. It is obvious that there is variety of localized corrosion in the initial stage of atmospheric corrosion.

3D seismic analysis of an Upper Palaeozoic carbonate succession of the Eastern Finnmark Platform area, Norwegian Barents Sea

This paper presents 3D seismic data to enhance our understanding of the seismic stratigraphy and buildup developments of the Finnmark Platform. We focus on carbonate buildup distributions and platform geometry in space and upper Palaeozoic time. Multi-attribute analysis, neural network techniques and the use of inverted impedance data reveal seismic anomalies that can be linked with significant geological geometries such as buildups, subtle prograding clinoforms, karstified surfaces or platform breaks. The seismic expressions show a platform development mainly driven by climatic changes and differential subsidence. Seismic data indicate the first progradation of a low angle warm-water carbonate ramp during Mid Carboniferous times. A gradual change from a low angle (mixed) carbonate ramp to a more restricted carbonate shelf with a marked break and slope occurs during Upper Carboniferous/Lower Permian (Gipsdalen Group). Large buildups on the platform are identified both as individual mounds and unique continuous complexes (e.g. network of polygonal ridges as well as a 30-km long barrier complex). Multi-attribute analysis reveals a distinct karst event on top of the Gipsdalen Group. Climatic cooling during the Lower Permian (Bjarmeland Group) resulted in an even more restricted platform as seen in the seismic data with developments of 200-m high bryozoan mounds in deeper waters of the platform slope. Further cooling during Mid Permian (Tempelfjorden Group) resulted in a major chert event with development of a series of spiculitic chert mounds.

Breccia dikes and crater‐related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary

Abstract— Environmental conditions on Mars are conducive to the modification and erosion of impact craters, potentially revealing the nature of their substructure. On Earth, postimpact erosion of complex craters in a wide range of target rocks has revealed the nature and distribution of craterrelated fault structures and a complex array of breccia and pseudotachylyte dikes, which range up to tens of meters in width and tens of kilometers in length. We review the characteristics of fault structures, breccia dikes, and pseudotachylyte dikes on Earth, showing that they occur in complex network‐like patterns and are often offset along late‐stage crater‐related faults. Individual faults and dikes can undulate in width and can branch and bifurcate along strike. Detailed geological analyses of terrestrial craters show that faults and breccia dikes form during each of the major stages of the impact‐cratering process (compression, excavation, and modification). We report here on the discovery of prominent, lattice‐like ridge networks occurring on the floor of a highly modified impact crater 75 km in diameter near the dichotomy boundary of the northern lowland and southern upland. Interior fill and crater‐floor units have been exhumed by fluvial and eolian processes to reveal a unit below the crater floor containing a distinctive set of linear ridges of broadly similar width and forming a lattice‐like pattern. Ridge exposures range from ˜1–4 km in length and ˜65–120 m in width, are broadly parallel, straight to slightly curving, and are cross‐cut by near‐orthogonal ridges, forming a box or lattice‐like pattern. Ridges are exposed on the exhumed crater floor, extending from the base of the wall toward the center. On the basis of the strong similarities of these features to terrestrial crater‐related fault structures and breccia dikes, we interpret these ridges to be faults and breccia dikes formed below the floor of the crater during the excavation and modification stages of the impact event, and subsequently exhumed by erosion. The recognition of such features on Mars will help in documenting the nature of impact‐cratering processes and aid in assessment of crustal structure. Faults and breccia dikes can also be used as data for the assessment of post‐cratering depths and degrees of landform exhumation.