Parallel Ridges Research Articles

Plastic ridge formation in a compressed thin amorphous film

We demonstrate that surface morphogenesis in compressed thin films may result from spatially correlated plastic activity. A soft glassy film strongly adhering to a smooth and rigid substrate and subjected to uniaxial compression, indeed, does not undergo any global elastic pattern-forming instability, but responds plastically via localized burst events that self-organize, leading to the emergence of a series of parallel ridges transverse to the compression axis. This phenomenon has been completely overlooked, but results from common features of the plastic response of glasses hence should be highly generic for compressed glassy thin films.

An intriguing new diapsid reptile with evidence of mandibulo-dental pathology from the early Permian of Oklahoma revealed by neutron tomography.

The initial stages of diapsid evolution, the clade that includes extant reptiles and the majority of extinct reptilian taxa, is surprisingly poorly known. Notwithstanding the hypothesis that varanopids are diapsids rather than synapsids, there are only four araeoscelidians and one neodiapsid present in the late Carboniferous and early Permian. Here we describe the fragmentary remains of a very unusual new amniote from the famous cave deposits near Richards Spur, Oklahoma, that we recognize as a diapsid reptile, readily distinguishable from all other early amniotes by the unique dentition and lower jaw anatomy. The teeth have an unusual reeding pattern on the crown (long parallel ridges with rounded surfaces), with some teeth posteriorly tilted and strongly recurved, while a ventral protuberance forms the anterior terminus of the dentary. Overall, the lower jaw is unusually slender with a flattened ventral surface formed by the dentary and splenial anteriorly and the angular in the mid-region. The presence of a very slender triradiate jugal revealed through computed tomography confirms the existence of a large lower temporal fenestra, while the medial edge of the maxilla and the anatomy of the palatine confirm the presence of a large suborbital fenestra. Computed tomography of this new taxon reveals maxillary innervation that is characteristically reptile, not synapsid. Although no other definitively identifiable skull roof elements exist, the suborbital fenestra borders preserved on the palatine and maxilla supports the hypothesis that this is a diapsid reptile. Interestingly, the right dentary shows evidence of pathology, a rarely reported occurrence in Paleozoic amniotes, with several empty tooth sockets filled by bone. This small predator with delicate subthecodont implanted dentition provides strong evidence that diapsid reptiles were already diversifying rapidly in the early Permian, but likely were relatively rare members of terrestrial vertebrate assemblages.

Improved High‐Resolution Bathymetry Map of Tamu Massif and Southern Shatsky Rise and Its Geologic Implications

AbstractThe formation and geology of oceanic plateaus are incompletely understood, in part because geophysical data are sparse and of low density. This paper presents an improved high‐resolution bathymetry map for southern Shatsky Rise, by combining newly acquired multibeam bathymetry data from several cruises and by filling in gaps in multibeam coverage with the SRTM15+ global bathymetry model. This map provides important insights on the evolution of Shatsky Rise from plateau forming, to post‐plateau secondary volcanism, to sedimentation, erosion, and sedimentary mass wasting. Tamu Massif is segmented by several subdued bathymetric troughs that divide the massif flanks into smaller rises. The segmentation pattern suggests Tamu Massif was built by a series of eruptions along a jumping triple junction. The distribution of secondary volcanic cones is non‐uniform, with most occurring on the southern and eastern flanks. Most of these secondary cones occur as short chains that parallel nearby magnetic lineations, suggesting control by spreading ridge parallel faults. These results suggest the evolution of Shatsky Rise was largely controlled by spreading ridges during its active volcanic phase. Numerous escarpments were identified around the plateau, a majority of which parallel bathymetry contours, suggesting these features developed because of differential subsidence of the rise massifs. The map reveals widespread mass wasting and downslope sediment movement, shifting sediment distribution and changing the surface morphology. Improved topography improves our understanding of the evolution of Shatsky Rise and emphasizes the importance of bathymetry data in deciphering the geodynamic evolution of large igneous provinces.

Mineralogy and Geochemistry of the Asanje Iron Ore Deposit within the Mayamaya-Hombolo Belt, Dodoma Region, Central Tanzania

This paper presents the mineralogy and chemical composition including iron ore impurities to ascertain its suitability for industrial applications. The Asanje iron ore deposit is hosted in Precambrian volcano-sedimentary rocks in the Mayamaya-Hombolo Belt in Dodoma region, within the Lake Nyanza Superterrane. Iron ores are found in two parallel ridges trending NW-SE. Ridge I occurs as vein and banded hematite-type ore and Ridge II as massive-type ore. A total of 24 ore samples were analysed for major and trace elements by XRF and petrographic studies by optical microscopy and XRD. The XRD results revealed that hematite and goethite are the main components and quartz is the gangue mineral in the iron ores. The XRF data shows the Fe2O3t content ranges from 20.8 to 87.3 wt% with an average of 52.7 wt%. The average concentrations in wt% of impurities such as SiO2, Al2O3, P2O5 and S are 37.9, 0.9, 1.2, and 0.2, respectively. By comparison, Ridge II has greater iron content (30.5–87.3 = Avg. 64.66 wt% Fe2O3t) than Ridge I (20.8–78.22 = Avg. 48.68 wt% Fe2O3t). Based on the chemical composition, the quality of iron ore is categorised as low to medium grade, and can be used in metallurgical and cement industries.
 Keywords: Mineralogy, Geochemistry, Asanje Iron ore deposit, Mayamaya-Hombolo Belt, Tanzania

Anatomic considerations for immediate implant placement in the mandibular molar region: a cross-sectional study using cone-beam computed tomography

There is concern regarding immediate implantation in the molar region because of discrepancy between socket size and inserted implant diameter. The purpose of this study was to assess the local anatomy of the posterior mandibular region in relation to immediate implant placement using cone-beam computed tomography (CBCT). Using CBCT imaging data, 204 mandibular first molars and 201 mandibular second molars were assessed for the interradicular and alveolar bone dimensions, tooth sizes and proximity to vital structures. The cross-sectional mandibular shape and root configuration of these molars were determined. Distances to the inferior alveolar canal (IAC) from the root apices of the first molar were significantly greater than the second molar. Up to 14.5% of second molars had less than 10 mm of vertical bone height between the IAC and furcation bone crest. Interradicular bone width of < 3 mm was found in 57% of second molars. All first molars in this study had two to three roots while 16% of second molars presented with a single root. The prevalent mandible shape at the first and second molars was the parallel and undercut ridges, respectively. The mandibular second molars from samples of a Southeast Asian population presented with greater anatomical difficulties for immediate implant placement which include absent or inadequate interradicular bone thickness, higher incidence of unfavourable mandible shape and increased proximity to vital structures.

Femtosecond Laser-Ablated Copper Surface as a Substrate for a MoS2-Based Hydrogen Evolution Reaction Electrocatalyst.

One of the methods to improve the performance of a heterogeneous electrocatalyst is the dispersion of a catalytic material on a suitable substrate. In this study, femtosecond laser ablation was used to prepare very rough but also ordered copper surfaces consisting of vertical, parallel ridges. Then, a molybdenum sulfide coating was electrochemically deposited onto these surfaces. It was observed by profilometry that the average roughness of the surface after coating with MoS2 had decreased, but the developed surface area still remained significantly larger than the projected surface area. The electrodes were then used as an electrocatalyst for the hydrogen evolution reaction in acidic media. These were highly efficient, reaching 10 mA cm−2 of HER current at a −181 mV overpotential and a Tafel slope of ~39 mV dec−1. Additionally, scanning electrochemical microscopy was used to observe whether hydrogen evolution would preferentially occur in certain spots, for example, on the peaks, but the obtained results suggest that the entire surface is active. Finally, the electrochemical impedance spectroscopy data showed the difference in the double-layer capacitance between the ablated and non-ablated surfaces (up to five times larger) as well as the parameters that describe the improved catalytic activity of fs-Cu/MoS2 electrodes.

Nanoscale pattern formation on silicon surfaces bombarded with a krypton ion beam: experiments and simulations

The nanoscale patterns produced by bombardment of the (100) surface of silicon with a 2 keV Kr ion beam are investigated both experimentally and theoretically. In our experiments, we find that the patterns observed at high ion fluences depend sensitively on the angle of incidence Θ. For Θ values between 74° and 85°, we observe five decidedly different kinds of morphologies, including triangular nanostructures traversed by parallel-mode ripples, long parallel ridges decorated by short-wavelength ripples, and a remarkable mesh-like morphology. In contrast, only parallel-mode ripples are present for low ion fluences except for Θ = 85°. Our simulations show that triangular nanostructures that closely resemble those in our experiments emerge if a linearly dispersive term and a conserved Kuramoto–Sivashinsky nonlinearity are appended to the usual equation of motion. We find ridges traversed by ripples, on the other hand, in simulations of the Harrison–Pearson–Bradley equation (Harrison et al 2017 Phys. Rev. E 96 032804). For Θ = 85°, the solid surface is apparently stable and simulations of an anisotropic Edwards–Wilkinson equation yield surfaces similar to those seen in our experiments. Explaining the other two kinds of patterns we find in our experiments remains a challenge for future theoretical work.

Significance of eggshell morphology as an additional tool to distinguish species of sand flies (Diptera: Psychodidae: Phlebotominae).

Morphological characteristics of eggshells are important in sand fly ootaxonomy. In this study, eggshells from Phlebotomus stantoni Newstead, Sergentomyia khawi (Raynal), and Grassomyia indica (Theodor) sand flies collected in Chiang Mai province, Thailand were examined and characterized using light microscopy (LM) and scanning electron microscopy (SEM). Then, eggshell morphology of these three species was described for the first time. Each gravid female was forced to lay eggs by decapitation and the eggs were collected for SEM analysis. Egg laying females were identified by morphological examination and molecular typing using cytochrome b (Cytb) as a molecular marker. The chorionic sculpturing of Ph. stantoni eggs combines two patterns on the same egg: unconnected parallel ridges and reticular patterns. Sergentomyia khawi and Gr. indica have similar chorionic polygonal patterns, but their exochorionic morphology and aeropylar area are different. Results indicate that eggshell morphological characteristics such as chorionic pattern, exochorionic morphology, inter-ridge/boundary area, aeropylar area (including the number of aeropyles) and basal layer, can be useful to develop morphological identification keys of eggs. These can serve as an additional tool to distinguish species of sand flies. In addition, the chorionic sculpturing of the eggs of the three species of sand flies observed by LM is useful for species identification in gravid females with spermathecae obscured by eggs.

Meso- to microscale modeling of atmospheric stability effects on wind turbine wake behavior in complex terrain

Abstract. Terrain-induced flow phenomena modulate wind turbine performance and wake behavior in ways that are not adequately accounted for in typical wind turbine wake and wind plant design models. In this work, we simulate flow over two parallel ridges with a wind turbine on one of the ridges, focusing on conditions observed during the Perdigão field campaign in 2017. Two case studies are selected to be representative of typical flow conditions at the site, including the effects of atmospheric stability: a stable case where a mountain wave occurs (as in ∼ 50 % of the nights observed) and a convective case where a recirculation zone forms in the lee of the ridge with the turbine (as occurred over 50 % of the time with upstream winds normal to the ridgeline). We use the Weather Research and Forecasting Model (WRF), dynamically downscaled from the mesoscale (6.75 km resolution) to microscale large-eddy simulation (LES) at 10 m resolution, where a generalized actuator disk (GAD) wind turbine parameterization is used to simulate turbine wakes. We compare the WRF–LES–GAD model results to data from meteorological towers, lidars, and a tethered lifting system, showing good qualitative and quantitative agreement for both case studies. Significantly, the wind turbine wake shows different amounts of vertical deflection from the terrain and persistence downstream in the two stability regimes. In the stable case, the wake follows the terrain along with the mountain wave and deflects downwards by nearly 100 m below hub height at four rotor diameters downstream. In the convective case, the wake deflects above the recirculation zone over 40 m above hub height at the same downstream distance. Overall, the WRF–LES–GAD model is able to capture the observed behavior of the wind turbine wakes, demonstrating the model's ability to represent wakes over complex terrain for two distinct and representative atmospheric stability classes, and, potentially, to improve wind turbine siting and operation in hilly landscapes.

Formation of magnetic nanowire arrays by cooperative lateral growth.

Nanowires typically grow along their longitudinal axis, and the long-range order among wires sustains only when a template exists. Here, we report an unprecedented electrochemical growth of ordered metallic nanowire arrays from an ultrathin electrolyte layer, which is achieved by solidifying the electrolyte solution below the freezing temperature. The thickness of the electrodeposit is instantaneously tunable by the applied electric pulses, leading to parallel ridges on webbed film without using any template. An array of metallic nanowires with desired separation and width determined by the applied pulses is formed on the substrate with arbitrary surface patterns by etching away the webbed film thereafter. This work demonstrates a previously unrecognized fabrication strategy that bridges the gap of top-down lithography and bottom-up self-organization in making ordered metallic nanowire arrays over a large area with low cost.

A new microbothriid monogenean Dermopristis pterophilus n. sp. from the skin of the Critically Endangered green sawfish Pristis zijsron Bleeker, 1851 (Batoidea: Pristidae) in Western Australia.

A new microbothriid monogenean Dermopristis pterophilus n. sp. is described from the skin of the Critically Endangered green sawfish Pristis zijsron Bleeker, 1851 in the Ashburton River delta, northern Western Australia. Analyses of the 28S ribosomal DNA marker and the molecular barcoding markers Histone 3 and Elongation Factor 1 α confirmed position among the Microbothriidae, with close affinity to the only other sequenced representative of Dermopristis Kearn, Whittington and Evans-Groing, 2010. The new species is morphologically consistent with the concept of Dermopristis; it has two testes, lacks a male copulatory organ and has a simple haptor. It is smaller than its two congeners D. paradoxus Kearn, Whittington and Evans-Gowing, 2010 and D. cairae Whittington and Kearn, 2011 and is most similar to the former, distinguished only in that it lacks the strong, transverse, parallel ridges on the ventral body surface that characterise that species. It is more easily distinguished from D. cairae, differing in body shape, possession of a seminal receptacle, and relative position and size of the haptor. It may further differ from both species by fine details of the gut diverticula, although these details are difficult to ascertain. Spermatophores were observed in the new species, similar to those previously reported for D. cairae. The new species exhibits site attachment preference: infections were greatest on and immediately adjacent to the host pelvic fins (including male reproductive organs, i.e. claspers), moderate in proximity to the dorsal and pectoral fins, few on the caudal fin and peduncle, and infrequently, isolated worms occurred elsewhere on the dorsal and ventral surfaces of the body. There was no incidence of infection on the head (including rostrum). We presume D. pterophilus is restricted to P. zijsron and thus likely faces the same threat of extinction.

Impacts of thrusting, extensional faulting, and glaciation on cratering records of Pluto’s largest moon Charon: Implications for the evolution of Kuiper belt objects

A first-order question in the studies of the Solar System is how its outer zone known as the Kuiper belt was created and evolved. Two end-member models, involving coagulation vs. streaming instability, make different predictions—testable by the cratering history of Kuiper Belt Objects (KBOs)—about the cumulative size-frequency distribution (SFD) of the KBOs. Among all of the imaged KBOs, Pluto’s largest icy moon, Charon, appears to preserve the largest size range of seemingly undisturbed craters, their diameters (<italic>D</italic>) on Charon ranging from &lt; 1 km to &gt; 220 km. Current work shows that Charon’s craters with <italic>D</italic> &lt; 10−20 km are fewer than those expected by the coagulation mechanism, but whether this is an artifact of post-cratering modification of smaller craters is unknown. We address this issue by conducting systematic photogeological mapping and performing detailed landform analysis using the highest resolution images obtained by the New Horizons spacecraft, which reveal a range of differentiable terrains on Charon. The most important findings of our work include (1) truncation and obliteration of large craters (diameters &gt; 30−40 km) and their crater rim ridges along the eastern edges of several north-trending, eastward-convex, arcuate ranges in Oz Terra of the northern encountered hemisphere, (2) lobate ridges, lobate knob trains, and lobate aprons resembling glacial moraine landforms on Earth, (3) dendritic channel systems containing hanging valleys, and (4) locally striated surfaces defined by parallel ridges, knob trains, and grooves that are &gt; 40−50 km in length. The above observations and the topographic dichotomy of Charon’s encountered hemisphere can be explained by a landscape-evolution model that involves (i) a giant impact that created the Vulcan Planitia basin and the extensional fault zone along its northern rim, (ii) a transient atmosphere capable of driving N₂-ice glacial erosion of the water-ice bedrock and transporting water-ice debris to sedimentary basins, (iii) regional glacial erosion and transport of earlier emplaced impact ejecta deposits from the highlands of Oz Terra into the lowland basin of Vulcan Planitia, (iv) syn-glaciation north-trending thrusting, interpreted to have been induced by Charon’s despinning, and (v) the development of a water-ice debris cover layer over subsurface N₂ ice below Vulcan Planitia during global deglaciation. The infilling of the Vulcan Planitia could have been accompanied by cryovolcanism. The extensive modification of impact craters means that the size-frequency distributions of Charon’s craters should serve only as a lower bound when used to test formation mechanisms proposed for Kuiper belt objects.

Angiosperm affinities of Surangea from the late Cretaceous Deccan Intertrappean Beds of central India

The genus Surangea Chitaley et Sheikh, based on permineralized specimens from the Deccan Intertrappean Beds of central India, was originally considered to represent a fern megasporangium. Reexamination of original material and new specimens has revealed that the structures are capsular fruits with well-defined seeds, rather than megasporangia. We describe Surangea fruits in detail, based on peels and micro-CT scanning, and document its distribution among multiple localities of the Deccan Intertrappean Beds. The fruits are pentacarpellate septicidal capsules with ~8–12 seeds per locule. The seeds are prominently ornamented with parallel ridges and have a curved embryo/endosperm cavity and a prominent aril. This set of features indicates eudicotyledonous affinities for Surangea. In particular, the combination of septicidal capsules, axile placentation and arillate campylotropus seeds suggests affinity with the order Myrtales, but it does not fit cleanly within an extant family. Surangea fruits add to the diversity of angiosperms known from this late Maastrichtian flora. It joins several other fruit types known from the Deccan flora that do not fall neatly into extant families, possibly representing parts of an endemic community that succumbed to environmental stress associated K-Pg boundary events and/or subsequent northward rafting of the Indian subcontinent.

Improvement of water wettability of gray cotton fabric using electron beam irradiation and supercritical CO2 treatment

In this study, the effect of electron beam (EB) and supercritical carbon dioxide (scCO2) treatments on the hydrophilicity of gray cotton pile fabric were investigated. The immersion time, an indicator of the hydrophilicity, was 19 s for a combination of the pre-EB irradiation and the post-scCO2 extraction. In contrast, the values were 13,750–13,990 s after EB irradiation and 65 s post-scCO2 treatment. The addition of a small amount of methanol or polyoxyethylene lauryl ether in scCO2 decreased the immersion time to 4 s or 2 s, which is the water wettability required for a towel product. ATR-FTIR analysis suggested the complete removal of waxy impurities from the gray cotton pile fabric by the combination treatment of EB and scCO2. It was also observed from the FE-SEM images that the visual structure of parallel ridges and grooves covering gray cotton fibers disappeared on fibers with a lower immersion time than 19 s, which suggested dewaxing (the removal of wax). The study reveals that EB irradiation and scCO2 are alternative waterless methods for improving the wettability of gray cotton fabrics.

Deep water cuspate stromatolites of the Cryogenian Trezona Formation.

Stromatolites and microbialites contain a rich repository of environmental and biological information. Despite extensive research, questions remain regarding the biological, chemical, and physical processes that control stromatolite macro, meso, and microstructure. We report unusual deep water cuspate stromatolites from the Cryogenian Trezona Formation, South Australia, from a mixed siliciclastic-carbonate open marine ramp setting. Cuspate stromatolite horizons develop near the base of decameter-scale transgression-regression cycles and typically overlie decimeter-scale irregular erosion surfaces. The cuspate structure within the stromatolites form near vertical, stacked cusp structures in cross section. In plan view, the cusps form cm-scale sharp parallel ridges oriented perpendicular to the regional downslope direction and perpendicular to the elongation direction of stromatolites. Stromatolites colonized topographic highs of irregular erosion surfaces (often hardgrounds) and grew in carbonate supersaturated, iron-rich marine waters in low turbidity sediment-starved settings. Cuspate stromatolites are interpreted as forming in deep water environments during maximum transgression as condensed intervals. Their microbial metabolism may require low light and low oxygen. A deep water origin for the Trezona Formation cuspate stromatolites and other Precambrian cuspate stromatolites suggests a link between the cuspate morphology and physical/chemical (carbonate supersaturated, low light, and low oxygen) conditions of Precambrian deep water marine settings.

Scanning electron microscopy of the palatine mucosa with connective tissue papillae of the Egyptian red fox (Vulpes vulpes aegyptiaca, Linnaeus, 1758).

The present study investigated the morphological, as well as the histological features of the Egyptian red fox's palate, in addition to the three-dimensional characteristics of the connective tissue papillae (CTP) of the palate by scanning electron microscopy (SEM). The hard palate was narrow rostrally and its width increased caudally. The maximum width was located at the caudal border of the upper fourth premolar tooth. The incisive papilla was represented by a rounded median elevation surrounded on each side by a groove on which the oral openings of the incisive ducts opened. The rostral part of the hard palate had 9-10 caudally concave transverse palatine ridges while the caudal part appeared smooth without ridges. The palatine raphe was indistinct rostrally but formed a groove caudally. By SEM, the palatine ridges had low projections. Different microplicae systems were present on the epithelial surface of the incisive papilla, palatine rugae, interrugal areas, and the smooth part. The CTP of the incisive papilla, palatine ridges, and soft palate were conical-shaped, cylindrical-shaped, and parallel serrated ridges, respectively. Histologically, the hard palate was lined by a cornified stratified squamous epithelium resting on a dense connective layer of lamina propria while the soft palate was lined by a noncornified stratified squamous epithelium. The palatine salivary glands were present in the smooth part of the hard palate and the soft palate. The information presented in the current study might serve as a reference guide for the interpretation of pathological conditions of the palate of red fox.

Origin of two different deformation styles via active folding mechanisms of inverted Abu El Gharadiq Basin, Western Desert, Egypt

The Abu El Gharadiq Basin (AGB) is one of the largest Cretaceous rift basins in the northern district of the Western Desert of Egypt. The AGB underwent tectonic inversion in the Upper Cretaceous through horizontal shortening in the NW-SE direction. Detailed interpretation of seismic sections across discrete regions of this basin shows that the rocks deformed in two different depth-related deformation styles, which are partitioned across the base of the so called Bahariya Formation of Cenomanian age. The deeper, pre-Cenomanian rock units show contractional deformation forming tight folds and related fabrics while shallower, post-Cenomanian rock units display features of extensional deformation. These are essentially shallowly undulating open folds, associated with conjugate normal faults and tensional fractures. The deeper pre-Cenomanian tight anticlines pierce the upper rock units as diapiric-like intrusions that are seen on the seismic sections as hazy regions. We infer that the two different deformation styles above and below the Cenomanian rocks occurred simultaneously. The hazy regions on the seismic sections may result from lateral flow of shale rocks that give rise to chaotic structures near the anticlines. Mechanical anisotropy across the Cennomanian rock unit is inferred to be the main cause of simultaneous emergence of contractional and extensional deformations. Re-evaluation of fracture patterns of the northern rift basins in the Western Desert implies that the AGB originated in an extensional stepover region of a discrete, ENE-WSE trending, shear zone whose margins underwent inversions, developing two parallel thrust-dominated ridges, namely the crustal scale Kattaniya and Qattara-Alamein ridges.

Finger‐Skin‐Inspired Flexible Optical Sensor for Force Sensing and Slip Detection in Robotic Grasping

AbstractThe finger skin of human plays a key role in amplifying and transferring tactile signals to sensory receptors, and it provides design guidelines for next‐generation flexible tactile sensors. To enable robotic applications such as dexterous manipulation and tactile feedback, the functions of force sensing and slip detection are crucial for flexible tactile sensors. Here, a finger‐skin inspired flexible optical (FIFO) sensor based on optical microfiber is reported, and this sensor has fingerprint‐like surface with parallel ridges and resin/polydimethylsiloxane multilayer structure with different stiffness, mimicking the structural characteristics of human finger skin. With these design features, the sensor is capable of measuring force with high durability and detecting slip with high sensitivity and short response time. Time‐resolved response curve and its wavelet transform provide useful information related to grasping and slipping when the sensor is in contact with objects with different shapes and materials. As a proof‐of‐concept demonstration, the sensor directly attached onto a robotic gripper is capable of measuring grasping force and monitoring object slippage during manipulation tasks, indicating its potential applications in advanced robotics.

Vascular Flora and Biogeographic Affinity of the Sevier Shale Knobs of Northeastern Tennessee

In the Ridge and Valley physiographic province, knobs stand out as anomalous landforms embedded within a region of long, parallel ridges and valleys. In northeastern Tennessee, knobs are associated with the Sevier shale. Well-drained, acidic, channery loam Montevallo soils cover uplands of these knobs. A flora of the Sevier shale knobs of northeastern Tennessee identified 265 taxa in 57 plant families of which 13.6% were exotic and three were state listed (Berberis canadensis, Ruellia purshiana, Silene caroliniana var. pensylvanica). Many taxa had rarely or never been collected in northeastern Tennessee. The flora of the Sevier shale knobs was most similar to dolomite and limestone barrens of southwestern Virginia but among the species rarely collected in northeastern Tennessee, the greatest number was shared with floras of the Sequatchie Valley, middle Tennessee cedar glades, and barrens of the Tennessee eastern Highland Rim.

Fabrication of a gradient hydrophobic surface with parallel ridges on pyrolytic carbon for artificial heart valves

Effective surface modification to endow pyrolytic carbon (PYC) with long-term anti-thrombotic performance is highly demanded. In this work, a gradient hydrophobic surface on PYC was prepared by creating parallel ridges via the combination of laser etching technology and surface fluorosilanization. Scanning electron microscopy (SEM) observation confirms that the gradient hydrophobic surface is composed of a bare PYC region and four regions of parallel ridges with varying distances. The gradient hydrophobic surface is stable in air, phosphate buffer solution (PBS), and flowing PBS. Additionally, the gradient hydrophobic surface on PYC shows spontaneous droplet motion and much lower flow resistance than bare PYC. Compared to bare PYC, the gradient hydrophobic surface on PYC exhibits better blood compatibility and anti-adhesion performance. The results presented in this paper confirm that creating a gradient hydrophobic surface is an effective way of achieving long-lasting anti-thrombosis property.