Multi-methodological three-dimensional investigation of a closed-system Pingo in Northwestern Canada

2021 ◽  
Author(s):  
Julius Kunz ◽  
Christof Kneisel
Keyword(s):  
Internal Structure ◽  
Closed System ◽  
Vegetation Type ◽  
Ice Core ◽  
Three Dimensional ◽  
Thermal Conditions ◽  
Surface Characteristics ◽  
Theoretical Models ◽  
Previous Theory ◽  
Vegetation Height

<p>The Mackenzie-Delta region is known for widespread permafrost and the association of different landforms, which are characteristic of a periglacial landscape development. Especially the density of closed-system pingos is nowhere on earth higher than in the area of the Tuktoyaktuk Peninsula. This type of pingos is common only in the continuous permafrost zone and is very sensitive to changing thermal conditions. In this study, we investigated the surface and subsurface conditions in the area of such a closed-system Pingo near Parsons Lake in the southern part of the Tuktoyaktuk Peninsula to study its internal structure and evolutional state. Therefore, we used a combined approach of electrical resistivity tomography (ERT), ground-penetrating radar (GPR) and manual frost probing. In addition, a high-resolution digital elevation model and an orthophoto were generated using in situ drone acquisitions. These enabled a detailed and areawide mapping of surface characteristics (e.g. vegetation height or type) and should contribute to the investigation of linkages between surface and subsurface characteristics.</p><p>Such a linkage could be observed comparing the mapped vegetation type and heights with active layer depths derived from manual frost probing and GPR measurements. Both parameters show a significant zonation in the area of the pingo and its surrounding. In addition, the results of the quasi three-dimensional ERT measurements could deliver new insights into the three-dimensional internal structure of the pingo and a massive ice core could be detected. However, the shape as well as the position of the massive ice core in relation to the elevated surface of the pingo differ from the previous theory of closed-system pingo formation and therefore raises some questions. Also the existence of a talik could be confirmed, but its position beside the ice core within the eastern flank of the pingo and not below the massive ice core also differs from the theoretical models and should be discussed.</p>

X-ray microtomography

1988 ◽  
Vol 46 ◽  
pp. 998-999
Author(s):  
H.W. Deckman ◽  
B.F. Flannery ◽  
J.H. Dunsmuir ◽  
K.D' Amico
Keyword(s):  
Computed Tomography ◽  
Internal Structure ◽  
Imaging Technique ◽  
Three Dimensional ◽  
Tissue Structure ◽  
Individual Element ◽  
X Ray ◽  
Non Invasive ◽  
Panoramic Imaging ◽  
Three Dimensional Images

We have developed a new X-ray microscope which produces complete three dimensional images of samples. The microscope operates by performing X-ray tomography with unprecedented resolution. Tomography is a non-invasive imaging technique that creates maps of the internal structure of samples from measurement of the attenuation of penetrating radiation. As conventionally practiced in medical Computed Tomography (CT), radiologists produce maps of bone and tissue structure in several planar sections that reveal features with 1mm resolution and 1% contrast. Microtomography extends the capability of CT in several ways. First, the resolution which approaches one micron, is one thousand times higher than that of the medical CT. Second, our approach acquires and analyses the data in a panoramic imaging format that directly produces three-dimensional maps in a series of contiguous stacked planes. Typical maps available today consist of three hundred planar sections each containing 512x512 pixels. Finally, and perhaps of most import scientifically, microtomography using a synchrotron X-ray source, allows us to generate maps of individual element.

scholarly journals Online Measurement of Deposit Surface in Electron Beam Freeform Fabrication

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 4001 ◽  
Author(s):  
Shuhe Chang ◽  
Haoyu Zhang ◽  
Haiying Xu ◽  
Xinghua Sang ◽  
Li Wang ◽  
...  
Keyword(s):  
Electron Beam ◽  
3D Reconstruction ◽  
Three Dimensional ◽  
Thermal Conditions ◽  
Online Measurement ◽  
Three Dimensional Reconstruction ◽  
Continuous Change ◽  
Position Information ◽  
Freeform Fabrication ◽  
Dimensional Reconstruction

In the process of electron beam freeform fabrication (EBF3), due to the continuous change of thermal conditions and variability in wire feeding in the deposition process, geometric deviations are generated in the deposition of each layer. In order to prevent the layer-by-layer accumulation of the deviation, it is necessary to perform online geometry measurement for each deposition layer, based on which the error compensation can be done for the previous deposition layer in the next deposition layer. However, the traditional three-dimensional reconstruction method that employs structured laser cannot meet the requirements of long-term stable operation in the manufacturing process of EBF3. Therefore, this paper proposes a method to measure the deposit surfaces based on the position information of electron beam speckle, in which an electron beam is used to bombard the surface of the deposit to generate the speckle. Based on the structured information of the electron beam in the vacuum chamber, the three-dimensional reconstruction of the surface of the deposited parts is realized without need of additional structured laser sensor. In order to improve the detection accuracy, the detection error is theoretically analyzed and compensated. The absolute error after compensation is smaller than 0.1 mm, and the precision can reach 0.1%, which satisfies the requirements of 3D reconstruction of the deposited parts. An online measurement system is built for the surface of deposited parts in the process of electron beam freeform fabrication, which realizes the online 3D reconstruction of the surface of the deposited layer. In addition, in order to improve the detection stability of the whole system, the image processing algorithm suitable for this scene is designed. The reliability and speed of the algorithm are improved by ROI extraction, threshold segmentation, and expansion corrosion. In addition, the speckle size information can also reflect the thermal conditions of the surface of the deposited parts. Hence, it can be used for online detection of defects such as infusion and voids.

Macromolecular Structure Visualization Tools at NCMI

2000 ◽  
Vol 6 (S2) ◽  
pp. 282-283
Author(s):  
Matthew Dougherty ◽  
Wah Chiu
Keyword(s):  
Human Factors ◽  
3D Visualization ◽  
Three Dimensional ◽  
Theoretical Models ◽  
Biological Research ◽  
Macromolecular Structure ◽  
X Ray ◽  
Visualization Tools ◽  
Types Of Information ◽  
3D Em

Sophisticated tools are needed to examine the results of cyro-microscopy. As the size and resolution of three dimensional macromolecular structures steadily improve, and the speed at with which they can be generated increases, researchers are finding they are inundated with larger datasets and at the same time are compelled to expediently evaluate these structures in unforeseen ways. Integration of EM data with other types of information is becoming necessary and routine; for example X-ray data, 3D EM reconstructions, and theoretical models, must be evaluated in concert to discount or propose hypothesis. To create such tools, the developer must take into account not only the empirical and theoretical possibilities, but also they must master the human factors and computational limits. During the last five years, the National Center for Macromolecular Imaging (NCMI) has progressed from a remedial 3D visualization capability to a collection of visualization tools allowing researchers to focus on the discovery phase of biological research.

The Growth of Pingos, Western Arctic Coast, Canada

1973 ◽  
Vol 10 (6) ◽  
pp. 979-1004 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Growth Rate ◽  
Pore Water ◽  
Closed System ◽  
Water Pressure ◽  
Ice Core ◽  
Growth Stages ◽  
Size And Shape ◽  
Western Arctic ◽  
Arctic Coast ◽  
Strong Control

The growth rates of 11 closed system pingos have been measured, by means of precise levelling of permanent bench marks anchored well down into permafrost, for the 1969–1972 period. As pingo growth decreases from the summit to the base, growth of the ice-core decreases from the center out to the periphery. The pingos have grown up in the bottoms of lakes which have drained rapidly and thus become exposed to permafrost aggradation. The specific site of growth is usually in a small residual pond where permafrost aggradation is retarded. The size and shape of a residual pond exercises a strong control upon the size and shape of the pingo which grows within it. The ice-core thickness equals the sum of the pingo height above the lake flat and the depth of the residual pond in which the pingo grew. Pingos tend to grow higher rather than both higher and wider. Pingos are believed to grow more by means of ice segregation than by the freezing of a pool of water. The water source, and the associated positive pore water pressure, result from permafrost aggradation in sands and silts in the lake bottom under a closed system with expulsion of pore water. The fastest growth rate of an ice-core, for the Western Arctic Coast, is estimated at about 1.5 m/yr, for the first one or two years. After that, the growth rate decreases inversely as the square root of time. The largest pingos may continue to grow for more than 1000 yr. Four growth stages are suggested. At least five pingos have commenced growth since 1935. As an estimate, probably 50 or more pingos are now growing along the coast.

scholarly journals Titanium oral implants: surface characteristics, interface biology and clinical outcome

2010 ◽  
Vol 7 (suppl_5) ◽  
Author(s):  
Anders Palmquist ◽  
Omar M. Omar ◽  
Marco Esposito ◽  
Jukka Lausmaa ◽  
Peter Thomsen
Keyword(s):  
Surface Properties ◽  
Cellular Response ◽  
Randomized Clinical Trials ◽  
Three Dimensional ◽  
Cell Communication ◽  
Surface Characteristics ◽  
Titanium Implants ◽  
Material Surface ◽  
Oral Implants

Bone-anchored titanium implants have revolutionized oral healthcare. Surface properties of oral titanium implants play decisive roles for molecular interactions, cellular response and bone regeneration. Nevertheless, the role of specific surface properties, such as chemical and phase composition and nanoscale features, for the biological in vivo performance remains to be established. Partly, this is due to limited transfer of state-of-the-art preparation techniques to complex three-dimensional geometries, analytical tools and access to minute, intact interfacial layers. As judged by the available results of a few randomized clinical trials, there is no evidence that any particular type of oral implant has superior long-term success. Important insights into the recruitment of mesenchymal stem cells, cell–cell communication at the interface and high-resolution imaging of the interface between the surface oxide and the biological host are prerequisites for the understanding of the mechanisms of osseointegration. Strategies for development of the next generation of material surface modifications for compromised tissue are likely to include time and functionally programmed properties, pharmacological modulation and incorporation of cellular components.

scholarly journals Biological and Mechanical Properties of Platelet-Rich Fibrin Membranes after Thermal Manipulation and Preparation in a Single-Syringe Closed System

2018 ◽  
Vol 19 (11) ◽  
pp. 3433 ◽  
Author(s):  
Dorottya Kardos ◽  
István Hornyák ◽  
Melinda Simon ◽  
Adél Hinsenkamp ◽  
Bence Marschall ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Cell Adhesion ◽  
Closed System ◽  
Three Dimensional ◽  
Glass Tube ◽  
Biological Properties ◽  
Platelet Rich Fibrin ◽  
Handling Characteristics ◽  
Freeze Dried

Platelet-rich fibrin (PRF) membrane is a three-dimensional biodegradable biopolymer, which consists of platelet derived growth factors enhancing cell adhesion and proliferation. It is widely used in soft and hard tissue regeneration, however, there are unresolved problems with its clinical application. Its preparation needs open handling of the membranes, it degrades easily, and it has a low tensile strength which does not hold a suture blocking wider clinical applications of PRF. Our aim was to produce a sterile, suturable, reproducible PRF membrane suitable for surgical intervention. We compared the biological and mechanical properties of PRF membranes created by the classical glass-tube and those that were created in a single-syringe closed system (hypACT Inject), which allowed aseptic preparation. HypACT Inject device produces a PRF membrane with better handling characteristics without compromising biological properties. Freeze-thawing resulted in significantly higher tensile strength and higher cell adhesion at a lower degradation rate of the membranes. Mesenchymal stem cells seeded onto PRF membranes readily proliferated on the surface of fresh, but even better on freeze/thawed or freeze-dried membranes. These data show that PRF membranes can be made sterile, more uniform and significantly stronger which makes it possible to use them as suturable surgical membranes.

Investigation of Three-Dimensional Flow in Microchannels With Patterned Surfaces

2007 ◽  
Author(s):  
Auro Ashish Saha ◽  
Sushanta K. Mitra
Keyword(s):  
Surface Tension ◽  
Flow Instability ◽  
Numerical Study ◽  
Three Dimensional ◽  
Surface Characteristics ◽  
Bottom Wall ◽  
Surface Tension Effect ◽  
Hydrophobic Region ◽  
Side Walls ◽  
Dimensional Simulation

A three-dimensional numerical simulation of flow in patterned microchannel with alternate layers of hydrophilic and hydrophobic surfaces at the bottom wall is studied here. Surface characteristics of the microchannel are accounted by specifying the contact angle and the surface tension of the fluid. Meniscus profiles with varying amplitude and shapes are obtained under the different specified surface conditions. Flow instability increases as the fluid at the bottom wall traverses alternately from hydrophilic region to hydrophobic region. To understand the surface tension effect of the side walls, a two-dimensional numerical study has also been carried out for the microchannel and the results are compared with three-dimensional simulation. The surface tension effect of the side walls enhances the capillary effect for three-dimensional case.

scholarly journals Roles of cell and microvillus deformation and receptor-ligand binding kinetics in cell rolling

2008 ◽  
Vol 295 (4) ◽  
pp. H1439-H1450 ◽  
Author(s):  
Parag Pawar ◽  
Sameer Jadhav ◽  
Charles D. Eggleton ◽  
Konstantinos Konstantopoulos
Keyword(s):  
Ligand Binding ◽  
Three Dimensional ◽  
Theoretical Models ◽  
Binding Kinetics ◽  
Cell Deformation ◽  
Receptor Ligand ◽  
Length Scales ◽  
Bond Behavior ◽  
Cell Rolling ◽  
Threshold Phenomenon

Polymorphonuclear leukocyte (PMN) recruitment to sites of inflammation is initiated by selectin-mediated PMN tethering and rolling on activated endothelium under flow. Cell rolling is modulated by bulk cell deformation (mesoscale), microvillus deformability (microscale), and receptor-ligand binding kinetics (nanoscale). Selectin-ligand bonds exhibit a catch-slip bond behavior, and their dissociation is governed not only by the force but also by the force history. Whereas previous theoretical models have studied the significance of these three “length scales” in isolation, how their interplay affects cell rolling has yet to be resolved. We therefore developed a three-dimensional computational model that integrates the aforementioned length scales to delineate their relative contributions to PMN rolling. Our simulations predict that the catch-slip bond behavior and to a lesser extent bulk cell deformation are responsible for the shear threshold phenomenon. Cells bearing deformable rather than rigid microvilli roll slower only at high P-selectin site densities and elevated levels of shear (≥400 s−1). The more compliant cells (membrance stiffness = 1.2 dyn/cm) rolled slower than cells with a membrane stiffness of 3.0 dyn/cm at shear rates >50 s−1. In summary, our model demonstrates that cell rolling over a ligand-coated surface is a highly coordinated process characterized by a complex interplay between forces acting on three distinct length scales.

Failure Analysis of Cementless Hip Joint Prosthesis

2013 ◽  
Vol 845 ◽  
pp. 403-407
Author(s):  
Natesan Dhandapani ◽  
A. Gnanavelbabu ◽  
M. Sivasankar
Keyword(s):  
Hip Joint ◽  
Low Cost ◽  
Three Dimensional ◽  
Surface Characteristics ◽  
Element Model ◽  
Von Mises Stress ◽  
Surface Model ◽  
Joint Prosthesis ◽  
Replacement Technique ◽  
Von Mises

In this changing global scenario, modification, transplantation, and replacement can be the eternal solution for most of the problems in the medical field. Hence replacement technique finds a very prominent place in medicine as a remedy having closely tied up with biomechanics. One of the most important joints in the human body is the hip joint, the big and complex joint. Many researches were conducted and many are in progress, but most of these works use simplified models with either 2D or 3D approaches. The hip joint is formed by four components like femoral head cortical bone, stem, and neck. In this system we can find orthotropic and isotropic materials working together. The main objective of this research is to develop a three dimensional surface and solid finite element model of the hip joint to predict stresses in its individual components. This model is a geometric non-linear model, which helps us understand its structural mechanical behavior, seeming to suggest with advanced research in the future new hip joint prosthesis, as well as to prove the prosthesis joint interaction before being implanted in the patient. This research explains a complete human hip joint model without cartilaginous tissue, using ANSYS 10.0 Multiphysics Analysis for nine different postures in hip joint using three different materials (CoCr, Ti6Al4V, and UHMWPE) to calculate fatigue life. The result obtained from the analysis of surface model and solid model serve to help in predicting the life cycle, surface characteristics, shear stress in XY plane, stress concentration and areas that are prone to failure. Von Mises stress on the surface of our model facilitates us to equip and design an optimized prosthesis device having unique materials composition , with a highly bio-compatible and durable alloy at a low cost could be produced. In this way, a first important step towards the structural characterization of human hip joint has been developed.

scholarly journals Use of stable water isotopes to identify stages of the pingo ice core formation

2018 ◽  
Vol 58 (4) ◽  
pp. 507-523 ◽  
Author(s):  
Ju. N. Chizhova ◽  
Yu. K. Vasil’chuk
Keyword(s):  
Closed System ◽  
Ice Core ◽  
Ice Cores ◽  
Water Isotopes ◽  
Ice Formation ◽  
Stable Water Isotopes ◽  
Additional Tool ◽  
Hydrological Conditions ◽  
Water Saturated ◽  
Average Annual Precipitation

Te isotopic characteristics of the pingo ice cores are considered. Te distribution of δ18O and δ2H values, dexc, δ18O–δ2H and δ2H–d exc relationships, and the simulation of the distribution of δ18O and δ2H values during the ice formation in a closed system, allowed drawing conclusion about the hydrological conditions and stages of the ice core growth. All pingos (Pestsovoye, Weather, Pingo-20) were formed in draining lake basins in the course of freezing of closed taliks. It is established that the water, which served as a source for the formation of the ice core, was subjected to evaporation still before the ice formation. According to our estimates, the water from which the ice of the Pestsovoye pingo was formed was heavier in values of δ18O and δ2H by 3.9 and 29.7‰, respectively, than the current average annual precipitation in the region. Similarly, for the ice of the core of the Pingo Weather it is 2.9 and 14.5‰, and 5.1 and 27.7‰ for the Pingo-20, respectively. In the ice cores of all considered pingos there is an ice formed in a closed system: in Pingo-20 it is a pure injection ice, while in the Pestsovoye and the Weser ones – the injected-segregated ice. Te frost mounds Pestsovoe and Weser grew under changing hydrological conditions: one part of the ice was formed when there was a free flow of water to the freezing front (open system); the other one – when the water-saturated lenses of the closed talik were frozen (closed system). Te isotopic composition of ice being formed under conditions of a closed system reflects isotopic depletion during freezing and ice formation according to the Rayleigh model. It is expressed in a successive decrease in the values of δ18O and δ2H from the frst portions of ice to the last ones as the freezing continued. Te contrast values of δ18O and δ2H in different parts of the ice being formed in the closed system may be used as an additional tool to identify direction of freezing. In a closed system, the last portions of ice have the greater contrast of the isotope values as compared to the frst portions.

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