INTERFACE DEPINNING FROM WEDGES WITH A CENTRAL RIDGE

2006 ◽  
pp. 359-363
Author(s):  
GILBERTO GIUGLIARELLI
Keyword(s):  
Central Ridge

scholarly journals Reductive dissolution of biogenic magnetite

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Toshitsugu Yamazaki
Keyword(s):  
Japan Sea ◽  
Depth Interval ◽  
Reductive Dissolution ◽  
Magnetic Minerals ◽  
Specific Chemical ◽  
Biogenic Magnetite ◽  
Transmission Electron ◽  
Dissolution Zone ◽  
Central Ridge ◽  
Redox Boundary

Abstract Reductive dissolution of magnetite is known to occur below the Fe-redox boundary in sediments. In this study, detailed processes associated with biogenic magnetite dissolution are documented. A sediment core from the Japan Sea was used for this purpose, in which reductive dissolution of magnetic minerals is known to start at depths of about 1.15 m and is mostly complete within a depth interval of about 0.35 m. Using first-order reversal curve diagrams, preferential dissolution of biogenic magnetite within this interval is estimated from the observation that a narrow peak that extends along the coercivity axis (central ridge), which is indicative of biogenic magnetite, diminishes downcore. Transmission electron microscopy is used to demonstrate that the sediments contain three magnetofossil morpho-types: octahedra, hexagonal prisms, and bullet-shaped forms. Within the reductive dissolution zone, partially etched crystals are commonly observed. With progressive dissolution, the proportion of bullet-shaped magnetofossils decreases, whereas hexagonal prisms become more dominant. This observation can be explained by the differences in resistance to dissolution among crystal planes of magnetite and the differences in surface area to volume ratios. Magnetofossil morphology may reflect the preference of magnetotactic bacterial lineages for inhabiting specific chemical environments in sediments. However, it could also reflect alteration of the original morphological compositions during reductive diagenesis, which should be considered when using magnetofossil morphology as a paleoenvironmental proxy.

scholarly journals A cadaveric study of the location and morphology of the central patellar ridge for bone-patellar tendon-bone graft

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Thanathep Tanpowpong ◽  
Thun Itthipanichpong ◽  
Thanasil Huanmanop ◽  
Nonn Jaruthien ◽  
Nattapat Tangchitcharoen
Keyword(s):  
Patellar Tendon ◽  
Cancellous Bone ◽  
Average Distance ◽  
Cadaveric Study ◽  
Anterior Cortex ◽  
Length Width ◽  
Central Ridge ◽  
The Mean ◽  
Bone Patellar Tendon ◽  
And Cartilage

Abstract Introduction The central ridge of the patella is the thickest area of patella and varies among patients. This cadaveric study identified the location and thickness of the bone at the central patella ridge for bone-patellar tendon-bone (BPTB) harvesting. Materials and methods Fifty cadaveric knees were assessed. First, the morphology, length, width, and location of the central patellar ridge were recorded. Then, we transversely cut the patella 25 mm from the lower pole and measured the thickness of the anterior cortex, cancellous bone, and cartilage from both the mid-patella and the central ridge location. Finally, the depth of the remaining cancellous bone at the mid-patella was compared to the bone at the central ridge. Results The location of the central-patellar ridge deviated medially from the mid-patella in 46 samples with an average distance of 4.36 ± 1 mm. Only 4 samples deviated laterally. The mean patella length was 41.19 ± 4.73 mm, and the width was 42.8 ± 5.25 mm. After a transverse cut, the remaining cancellous bone was significantly thicker at the central ridge compared to the bone at the mid-patella. Conclusions Most of the central patellar ridge deviated medially, approximately 4 mm from the mid-patella. Harvesting the graft from the central ridge would have more remaining bone compared to the mid-patella.

Variations in mixed-layer illite/smectite diagenesis in the rift and post-rift sediments of the Jeanne d'Arc Basin, Grand Banks offshore Newfoundland, Canada

2004 ◽  
Vol 41 (4) ◽  
pp. 401-429 ◽  
Author(s):  
Iftikhar A Abid ◽  
Reinhard Hesse ◽  
John D Harper
Keyword(s):  
Mixed Layer ◽  
Fine Fraction ◽  
Upper Jurassic ◽  
Grand Banks ◽  
Depth Profiles ◽  
Jeanne D'arc Basin ◽  
Central Ridge ◽  
Jeanne D'arc ◽  
Layer I ◽  
Mixed Layers

Mixed-layer illite/smectite (I/S) clays were analyzed from 22 deep exploration wells from the Jeanne d'Arc Basin on the Grand Banks offshore Newfoundland, the host of large commercial hydrocarbon accumulations discovered in the last two and a half decades. The fine fraction of the clays (<0.1 µm) consists mainly of mixed-layer I/S with minor amounts of kaolinite, illite, and chlorite. Smectite and (or) smectite-rich I/S clays were supplied to the Jeanne d'Arc Basin from Upper Jurassic to Tertiary times. Smectite-rich I/S clays occur only in shallow samples irrespective of geologic age. The proportion of illite in I/S mixed-layers, as well as the degree of ordering, increase with depth and temperature indicating that smectite-rich I/S clays have been progressively illitized in both rift and post-rift sediments of the Jeanne d'Arc Basin during burial. The transition from random to R1-ordered I/S occurs between subsurface depths of 1940 and 3720 m and crosses major stratigraphic boundaries. The transition from R1- to R3-ordered I/S generally occurs below 4000 m depth. Variable shapes of I/S depth profiles reflect the influence of temperature, fluid migration, subsidence history, basin structure, lithology, and salt diapirism on I/S diagenesis. Based on these variations, the basin can be subdivided into 4 regions with different illitization gradients. In the Southern Jeanne d'Ac Basin, advanced I/S diagenesis probably reflects uplift and denudation and (or) higher paleogeothermal gradients. Rapid increase of percent illite in I/S with depth in the Trans-Basinal Fault area is most likely controlled by upward flow of hot, K+-bearing fluids along faults. The migration of hydrocarbons probably followed the same pathways as the illitizing fluids. Delayed illitization in the Northern Jeanne d'Arc Basin and Central Ridge area reflects insufficient K+ supply because of a lack of detrital K-feldspar in the host sediment, the absence of faulting, and the presence of thick shale intervals. These findings show that I/S depth profiles may vary within the same sedimentary basin due to a variety of geological factors. Single wells generally cannot be considered representative for the basin as a whole.

Horizontal Central Ridge of the Lamina Cribrosa and Regional Differences in Laminar Insertion in Healthy Subjects

2012 ◽  
Vol 53 (3) ◽  
pp. 1610 ◽  
Author(s):  
Sung Chul Park ◽  
Saman Kiumehr ◽  
Christopher C. Teng ◽  
Celso Tello ◽  
Jeffrey M. Liebmann ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Regional Differences ◽  
Lamina Cribrosa ◽  
Central Ridge

scholarly journals Assessing Sediment-Nutrient Export Rate and Soil Degradation in Mai-Negus Catchment, Northern Ethiopia

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Gebreyesus Brhane Tesfahunegn ◽  
Paul L. G. Vlek
Keyword(s):  
Soil Degradation ◽  
Soil Samples ◽  
Northern Ethiopia ◽  
Nutrient Export ◽  
Replacement Cost ◽  
Soil Calcium ◽  
Standard Procedures ◽  
Central Ridge ◽  
Nutrient Replacement ◽  
Potassium Magnesium

Even though soil degradation challenges sustainable development, the use of degradation indicators such as nutrient export (NE) and nutrient replacement cost is not well documented at landform level. This study is aimed to investigate the extent of soil degradation, NE rates, and their replacement cost across landforms in the Mai-Negus catchment, northern Ethiopia. Different erosion-status sites (aggrading, stable, and eroded) in the landforms were identified, and soil samples were randomly collected and analysed. Nutrient export, replacement cost, and soil degradation were calculated following standard procedures. This study showed that soil degradation in the eroded sites ranged from 30 to 80% compared to the corresponding stable site soils, but the highest was recorded in the mountainous and central ridge landforms. Average NE of 95, 68, 9.1, 3.2, 2.5, and 0.07 kg ha−1 y−1 for soil calcium, carbon, nitrogen, potassium, magnesium, and phosphorus, respectively, was found from the landforms. Significantly strong relationships between NE and sediment yield in the landforms were observed. Annual nutrient replacement costs varied among the landforms though the highest was in the reservoir (€9204 in May 2010). This study thus suggests that while introducing antierosion measures, priority should be given to erosion sources to the reservoir such as mountainous and central ridge landforms.

scholarly journals A new depositional model for the Tuaheni Landslide Complex, Hikurangi Margin, New Zealand

2020 ◽  
Vol 500 (1) ◽  
pp. 551-566 ◽  
Author(s):  
Benjamin Couvin ◽  
Aggeliki Georgiopoulou ◽  
Joshu J. Mountjoy ◽  
Lawrence Amy ◽  
Gareth J. Crutchley ◽  
...  
Keyword(s):  
Seismic Data ◽  
Lateral Spreading ◽  
3D Seismic ◽  
Depositional Processes ◽  
Attribute Analysis ◽  
Internal Structures ◽  
Show Evidence ◽  
Levee System ◽  
Central Ridge ◽  
International Ocean Discovery Program

AbstractThe Tuaheni Landslide Complex (TLC) is characterized by areas of compression upslope and extension downslope. It has been thought to consist of a stack of two genetically linked landslide units identified from seismic data. We used 3D seismic reflection, bathymetry data and International Ocean Discovery Program Core U1517C (Expedition 372) to understand the internal structures, deformation mechanisms and depositional processes of the TLC deposits. Units II and III of U1517C correspond to the two chaotic units in 3D seismic data. In the core, Unit II shows deformation, whereas Unit III appears more like an in situ sequence. Variance attribute analysis showed that Unit II is split into lobes around a coherent stratified central ridge and is bounded by scarps. By contrast, we found that Unit III is continuous beneath the central ridge and has an upslope geometry, which we interpreted as a channel–levee system. Both units show evidence of lateral spreading due to the presence of the Tuaheni Canyon removing support from the toe. Our results suggest that Units II and III are not genetically linked, are separated substantially in time and had different emplacement mechanisms, but they fail under similar circumstances.

2. Observations on some New Species of British Fishes

1845 ◽  
Vol 1 ◽  
pp. 150-152
Author(s):  
Parnell
Keyword(s):  
New Species ◽  
The Body ◽  
The Other ◽  
Lower Margin ◽  
Central Ridge

The author stated that a species of sturgeon, for which he has proposed the name of Acipenser latirostris, as characteristic of the species, is occasionally met with in the Frith of Forth, in the Solway Frith and in the Tay. It is called by the fishermen the Broad-nosed Sturgeon, to distinguish it from the Acipenser sturio, or sharp-nosed species. The length, in general, seven feet; weight, about eight stone. The colour of the head, back, and sides, is of an olive-grey; the belly dirty white. The body is armed with five rows of osseous shields, extending from the head to the tail. The first row runs down the central ridge of the back. The two next rows arise one on each side of the former, and immediately on the lower margin of the pectorals the other two rows commence. The dorsal shields are but very slightly carinated, the fifth being the highest in the series.

scholarly journals Does the Symmetry of Patellar Morphology Matter When Matching Osteochondral Allografts for Osteochondral Defects Involving the Central Ridge of the Patella?

2020 ◽  
Vol 8 (7_suppl6) ◽  
pp. 2325967120S0044
Author(s):  
Nabeel Salka ◽  
Austin Ramme ◽  
John Grant ◽  
Jaron Scott ◽  
Karan Patel
Keyword(s):  
Surface Morphology ◽  
Pearson Correlation ◽  
Random Number Generator ◽  
Patellar Height ◽  
Osteochondral Defects ◽  
Surface Mapping ◽  
Significant Difference ◽  
Central Ridge ◽  
Clinically Significant ◽  
Osteochondral Allografts

Objectives: Osteochondral allografts of the patellar are currently matched solely based on tibial width. It is currently unknown whether matching by tibial width is a reasonable surrogate measurement to allow for optimum chondral surface matching or if patellar size and/or surface morphology (i.e., Wiberg classification) should be taken into account. This consideration may be especially important for chondral defects on the patellar apex. The purpose of this study was to use circumferential step-off height and chondral surface mapping to determine if differences in patellar surface morphology (i.e., Wiberg classification) play a role in the ability of donor patellar osteochondral allografts to match the native patellar surface when treating osteochondral defects involving the central ridge of the patella. The secondary purpose was to explore the relationship between tibial width and patellar size (width and height) to determine if tibial width strongly related to patellar size to allow it to act as a surrogate measure for patellar size. Methods: Twenty (10 Wiberg I and 10 Wiberg II/III) fresh frozen patellae were designated as the recipient. Each recipient was size-matched (within ± 2mm tibial width) to both a Wiberg I and a Wiberg II/III patellar donor to produce 20 size-matched trios. All patellas were classified as Wiberg I, II, or III by visual inspection. The patellar height and widths were also measured. The recipient patella underwent initial nanoCT scanning to quantify the native chondral surface morphology. A 16mm circular osteochondral “defect” centered on the central ridge of the patella was then created in the recipient patella. Within each set of three patellae, the donor Wiberg I and Wiberg II/III patellae were randomly assigned, using a random number generator, to be transplanted first or second. The randomly ordered donor Wiberg I or Wiberg II/III plug was harvested from a homologous location and transplanted into the recipient. The recipient was then nano-CT scanned, digitally reconstructed, registered to the initial nano-CT scan of the recipient patella. It was then processed in Dragon Fly to determine circumferential step-off heights between the native and donor surfaces at three degree intervals. This was calculated for the entire circumference and for each quadrant (superior, medial, inferior, lateral) to determine if the ste-off heights varied by locations. MATLAB was used to determine the height deviation (dRMS) between the native and donor surfaces at over 3000 surface points (Figure 1). The initial transplant was carefully removed and the process was then repeated for the other donor allograft. Pearson correlation coefficient, 2-way ANOVA with Tukey’s multiple comparison, and paired t-tests were used when appropriate. Sample size of 10 trios was determined based on previous work in our lab (clinically relevant difference of 0.75mm, SD = 0.5mm, α = 0.05, power 0.8; 7 samples per group). Results: There was no significant difference in mean step-off heights between matched and unmatched Wiberg allograft plugs (Table 1). When analyzing all patellas, the superior (p = 0.01) and lateral (p = 0.001) quadrants demonstrated step-off heights that were significantly greater compared to the inferior quadrant, however these findings were not clinically significant. There was a statistically significant difference in height deviation over the whole surface between native and donor plugs when comparing matched and unmatched Wiberg plugs (p=0.049), however this finding was not clinically significant (Table 2). There was no difference across individual quadrants. There was a linear correlation when comparing tibial width to patellar width (r = 0.82) and patellar height (r = 0.68). Conclusions: Differences in Wiberg classification did not lead to clinically relevant differences in step-off height or surface height deviations for the whole donor plug or by quadrant. Tibial width is a reasonable measure to predict patellar size (width and height). It is therefore reasonable to continue matching osteochondral allografts of the patella based on the easy to measure value of tibial width without consideration for patellar size or Wiberg classification. [Table: see text][Table: see text]

The Geology and Fossils of Carriacou, West Indies

1935 ◽  
Vol 72 (12) ◽  
pp. 529-555 ◽  
Author(s):  
C. T. Trechmann
Keyword(s):  
West Indies ◽  
Lesser Antilles ◽  
Central Ridge

Carriacou, the largest of the Grenadines lying between Grenada and St. Vincent, is the only one, so far as is known, of that group of islands which is not predominantly volcanic in origin. It may be described as the only limestone, or largely limestone, island in the whole inner arc of the Lesser Antilles which comprises Grenada, the Grenadines, St. Lucia, Martinique, Guadeloupe (west half), Montserrat, Nevis, St. Kitts, St. Eustatius, and Saba. Carriacou is 6¾ miles long and 2⅓ in greatest width and at High North Hill and Chapeau Carré rises to 980 and 960 feet. The remainder of the island is rugged and has several lesser peaks and a central ridge, running roughly north to south, 600–830 feet in height.

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