Littérature scientifique sur le sujet « Irregular cell space »
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Articles de revues sur le sujet "Irregular cell space"
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Mescia, Luciano, Michele Alessandro Chiapperino, Pietro Bia, Claudio Maria Lamacchia, Johan Gielis et Diego Caratelli. « Design of Electroporation Process in Irregularly Shaped Multicellular Systems ». Electronics 8, no 1 (1 janvier 2019) : 37. http://dx.doi.org/10.3390/electronics8010037.
Texte intégralRésumé :
Electroporation technique is widely used in biotechnology and medicine for the transport of various molecules through the membranes of biological cells. Different mathematical models of electroporation have been proposed in the literature to study pore formation in plasma and nuclear membranes. These studies are mainly based on models using a single isolated cell with a canonical shape. In this work, a space–time (x,y,t) multiphysics model based on quasi-static Maxwell’s equations and nonlinear Smoluchowski’s equation has been developed to investigate the electroporation phenomenon induced by pulsed electric field in multicellular systems having irregularly shape. The dielectric dispersion of the cell compartments such as nuclear and plasmatic membranes, cytoplasm, nucleoplasm and external medium have been incorporated into the numerical algorithm, too. Moreover, the irregular cell shapes have been modeled by using the Gielis transformations.
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Ocko, Samuel A., Kiah Hardcastle, Lisa M. Giocomo et Surya Ganguli. « Emergent elasticity in the neural code for space ». Proceedings of the National Academy of Sciences 115, no 50 (27 novembre 2018) : E11798—E11806. http://dx.doi.org/10.1073/pnas.1805959115.
Texte intégralRésumé :
Upon encountering a novel environment, an animal must construct a consistent environmental map, as well as an internal estimate of its position within that map, by combining information from two distinct sources: self-motion cues and sensory landmark cues. How do known aspects of neural circuit dynamics and synaptic plasticity conspire to accomplish this feat? Here we show analytically how a neural attractor model that combines path integration of self-motion cues with Hebbian plasticity in synaptic weights from landmark cells can self-organize a consistent map of space as the animal explores an environment. Intriguingly, the emergence of this map can be understood as an elastic relaxation process between landmark cells mediated by the attractor network. Moreover, our model makes several experimentally testable predictions, including (i) systematic path-dependent shifts in the firing fields of grid cells toward the most recently encountered landmark, even in a fully learned environment; (ii) systematic deformations in the firing fields of grid cells in irregular environments, akin to elastic deformations of solids forced into irregular containers; and (iii) the creation of topological defects in grid cell firing patterns through specific environmental manipulations. Taken together, our results conceptually link known aspects of neurons and synapses to an emergent solution of a fundamental computational problem in navigation, while providing a unified account of disparate experimental observations.
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CRESSON, JACKY. « NON-DIFFERENTIABLE DEFORMATIONS OF ℝn ». International Journal of Geometric Methods in Modern Physics 03, no 07 (novembre 2006) : 1395–415. http://dx.doi.org/10.1142/s0219887806001752.
Texte intégralRésumé :
Many problems of physics or biology involve very irregular objects like the rugged surface of a malignant cell nucleus or the structure of space-time at the atomic scale. We define and study non-differentiable deformations of the classical Cartesian space ℝn which can be viewed as the basic bricks to construct irregular objects. They are obtained by taking the topological product of n-graphs of nowhere differentiable real valued functions. Our point of view is to replace the study of a non-differentiable function by the dynamical study of a one-parameter family of smooth regularization of this function. In particular, this allows us to construct a one-parameter family of smooth coordinates systems on non-differentiable deformations of ℝn, which depend on the smoothing parameter via an explicit differential equation called a scale law. Deformations of ℝn are examples of a new class of geometrical objects called scale manifolds which are defined in this paper. As an application, we derive rigorously the main results of the scale-relativity theory developed by Nottale in the framework of a scale space-time manifold.
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Luza, J. G., R. van Gorsel, V. S. Polito et A. A. Kader. « Chilling Injury in Peaches : A Cytochemical and Ultrastructural Cell Wall Study ». Journal of the American Society for Horticultural Science 117, no 1 (janvier 1992) : 114–18. http://dx.doi.org/10.21273/jashs.117.1.114.
Texte intégralRésumé :
Fruits of mid- (`O'Henry'), late (`Airtime'), and extra-late-season (`Autumn Gem') peach [Prunus persica (L.) Batsch] cultivars were examined for changes in cell wall structure and cytochemistry that accompany the onset of mealiness and leatheriness of the mesocarp due to chilling injury. The peaches were stored at 10C for up to 18 days or at SC for up to 29 days. Plastic-embedded sections were stained by the Schiff's-periodic acid reaction, Calcofluor white MR2, and Coriphosphine to demonstrate total insoluble carbohydrates, ß-1,4 glucans, and pectins, respectively. Mealiness was characterized by separation of mesocarp parenchyma cells leading to increased intercellular spaces and accumulation of pectic substances in the intercellular matrix. Little structural change was apparent in the cellulosic component of the cell walls of these fruits. In leathery peaches, the mesocarp parenchyma cells collapsed, intercellular space continued to increase, and pectin-positive staining in the intercellular matrix increased greatly. In addition, the component of the cell walls that stained positively for ß-1,4 glucans became thickened relative to freshly harvested or mealy fruit. At the ultrastructural level, dissolution of the middle lamella, cell separation, irregular thickening of the primary wall, and plasmolysis of the mesocarp parenchyma cells were seen as internal breakdown progressed.
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Inoue, S. « Possible continuity of subplasmalemmal cytoplasmic network with basement membrane cord network : ultrastructural study ». Journal of Cell Science 108, no 5 (1 mai 1995) : 1971–76. http://dx.doi.org/10.1242/jcs.108.5.1971.
Texte intégralRésumé :
The ultrastructure of the subplasmalemmal cytoplasm of the cell and the associated basement membrane as well as the area of the cell-basement membrane border were observed with high resolution electron microscopy after preparation of the tissues with cryofixation or glutaraldehyde fixation followed by freeze substitution. The subplasmalemmal cytoplasm of the smooth muscle cells of rat epididymal tubules and the podocyte processes of the mouse glomerular visceral epithelium were found to be composed of a fine network of irregular anastomosing strands. This network closely resembled the previously characterized cord network of the basement membrane. The cords are known to be composed of a 1.5 to 3 nm thick core filament made up of type IV collagen which is surrounded by an irregular ‘sheath’ of other components. The strands in the subplasmalemmal network showed ultrastructural features similar to those of the cord network. Ribbon-like, 4.5 nm wide heparan sulfate proteoglycan ‘double tracks’ were previously reported to be associated with the cord network. Structures similar in size and appearance to the double tracks were also found in the subplasmalemmal network. At the cell-basement membrane border, the lamina densa of the basement membrane was in contact with the cell without the intervening space of a lamina lucida which was recently found to be an artefact caused by conventional tissue processing. Furthermore, the subplasmalemmal network appeared to be continuous through the plasma membrane, with the cord network of the basement membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
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Et. al., Mrs M. Anline Rejula,. « Medical Image Segmentation Of Wbc Using Improved Dual Threshold Method ». Turkish Journal of Computer and Mathematics Education (TURCOMAT) 12, no 10 (28 avril 2021) : 6129–43. http://dx.doi.org/10.17762/turcomat.v12i10.5450.
Texte intégralRésumé :
segmentation of medical images is a critical method for the proper identification and diagnosis of diseases. Because of the distinction between them, the segmentation of the WBCs is an important issue.The automatic diagnosis of multiple white blood cell or leukocyte disorders plays a significant role. The suggested work is an Improved Dual-Threshold approach based on a variation of white blood cell (WBC) segmentation of different color spaces. The improved dual-threshold segmentation method consists of three stages: the pre-processing stage, the segmentation step of the threshold, and the post-procurement phase. For additional handling, two images are obtained: one is a contrast-stretched grey image and the other is an H part image from the altered colour space of YCbCr in the pre-processing step. The three main steps comprising the threshold segmentation are context separation, red blood cell extraction, and the finest threshold selection.The single-threshold method in RGB colour space is involved in the process of separation of Red Blood Cells (RBC), the H channel image is used in the step of background extraction. The Golden Section search method is used for the best threshold selection item. Finally, to eliminate the noise and the unfinished
WBCs, median filtering and arithmetical morphology are used in the post-processing stage. The image data collection for Acute Lymphoblastic Leukaemia (ALL) is used to test and segment irregular cells from test data using an overall accuracy. Compared to the current segmentation outcome, the implemented segmentation approach shows better precision performance.
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Fuchs, M., M. K. Jones et K. L. Williams. « Characterisation of an epithelium-like layer of cells in the multicellular Dictyostelium discoideum slug ». Journal of Cell Science 105, no 1 (1 mai 1993) : 243–53. http://dx.doi.org/10.1242/jcs.105.1.243.
Texte intégralRésumé :
Ultrarapid freezing (RF) followed by freeze-substitution (FS) provide superior preservation of the Dictyostelium discoideum multicellular slug tissue over conventional methods of chemical fixation at room temperature. The peripheral cells of slugs prepared by RF and FS form a tight layer of flattened cells. This cell layer resembles epithelia of other multicellular organisms in that it has close junctional contact between cells associated with the extracellular matrix (ECM, slime sheath). This is the first report that clearly demonstrates the existence of such peripheral cellular specialisation in this otherwise well-studied model system. Junctional contacts between adjacent cells mean that there is no intercellular space evident between apical membranes of apposing cells, and basally the intermembraneous space between peripheral cells is less than 10 nm. By contrast, the intercellular space between internal cells is approximately 10–25 nm. The shape of the peripheral cells varies with their location around the slug. In the posterior prespore zone, the peripheral cells are squamous and exhibit polarity along their antero-posterior axis. In the anterior prestalk zone, peripheral cells are less flattened, project irregular filipodia between internal cells, and are polarised along their apical-basal axis. Colloidal gold immunocytochemistry with the markers MUD1, MUD50 and MUD62 demonstrated that the peripheral layer is formed of prestalk cells in the anterior region and ventrum, and mostly prespore cells along the dorsum. Thus, the peripheral layer, while having specific cell classes in different regions, is not differentiation-specific. Rather, it appears that the structure of these epithelium-like cells is influenced by interaction with molecules of the ECM (sheath).
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Guio, P., et H. L. Pécseli. « Phase space structures generated by absorbing obstacles in streaming plasmas ». Annales Geophysicae 23, no 3 (30 mars 2005) : 853–65. http://dx.doi.org/10.5194/angeo-23-853-2005.
Texte intégralRésumé :
Abstract. The dynamic behavior of a collisionless plasma flowing around an obstacle is investigated by numerical methods. In the present studies, the obstacle is formed by an absorbing cylinder, and a 2-D electrostatic particle-in-cell simulation is used to study the flow characteristics, with extensions to a fully 3-D generalization of the problem demonstrated as well. The formation of irregular filamented density depletions, oblique to the flow, is observed. The structures form behind the obstacle, in a region with a strong velocity shear, but also other instability mechanisms can be identified. The dynamics of these structures is highly dependent on the physical parameters of the plasma, and they can either be quasi-stationary or undergo a dynamic evolution. The structures are found to be associated with phase-space vortices, observed especially in the phase space spanned by the velocity direction perpendicular to the flow and the spatial coordinate in the same direction. The bias of the obstacle with respect to the plasma potential is found to be an important parameter for the dynamics of the structures, but seemingly not for their formation as such. The results can be of interest in the interpretation of structures in space plasmas as observed by instrumented spacecrafts.
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TANAKA, SATOSHI, KYOKO HASEGAWA, SUSUMU NAKATA, HIDEO NAKAJIMA, TAKUYA HATTA, FREDERIKA RAMBU NGANA, TAKUMA KAWAMURA, NAOHISA SAKAMOTO et KOJI KOYAMADA. « GRID-INDEPENDENT METROPOLIS SAMPLING FOR VOLUME VISUALIZATION ». International Journal of Modeling, Simulation, and Scientific Computing 01, no 02 (juin 2010) : 199–218. http://dx.doi.org/10.1142/s1793962310000158.
Texte intégralRésumé :
We propose a method of sampling regular and irregular-grid volume data for visualization. The method is based on the Metropolis algorithm that is a type of Monte Carlo technique. Our method enables "importance sampling" of local regions of interest in the visualization by generating sample points intensively in regions where a user-specified transfer function takes the peak values. The generated sample-point distribution is independent of the grid structure of the given volume data. Therefore, our method is applicable to irregular grids as well as regular grids. We demonstrate the effectiveness of our method by applying it to regular cubic grids and irregular tetrahedral grids with adaptive cell sizes. We visualize volume data by projecting the generated sample points onto the 2D image plane. We tested our sampling with three rendering models: an X-ray model, a simple illuminant particle model, and an illuminant particle model with light-attenuation effects. The grid-independency and the efficiency in the parallel processing mean that our method is suitable for visualizing large-scale volume data. The former means that the required number of sample points is proportional to the number of 2D pixels, not the number of 3D voxels. The latter means that our method can be easily accelerated on the multiple-CPU and/or GPU platforms. We also show that our method can work with adaptive space partitioning of volume data, which also enables us to treat large-scale/complex volume data easily.
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Soroka, C. J., et M. G. Farquhar. « Characterization of a novel heparan sulfate proteoglycan found in the extracellular matrix of liver sinusoids and basement membranes. » Journal of Cell Biology 113, no 5 (1 juin 1991) : 1231–41. http://dx.doi.org/10.1083/jcb.113.5.1231.
Texte intégralRésumé :
A novel heparan sulfate proteoglycan (HSPG) present in the extracellular matrix of rat liver has been partially characterized. Proteoglycans were purified from a high salt extract of total microsomes from rat liver and found to consist predominantly (approximately 90%) of HSPG. A polyclonal antiserum raised against this fraction specifically recognized HSPG by immunoprecipitation and immunoblotting. The intact, fully glycosylated HSPG migrated as a broad smear (150-300 kD) by SDS-PAGE, but after deglycosylation with trifluoromethanesulfonic acid only a single approximately 40-kD band was seen. By immunocytochemistry this HSPG was localized in the perisinusoidal space of Disse associated with irregular clumps of basement membrane-like extracellular matrix material, some of which was closely associated with the hepatocyte sinusoidal cell surface. It was also localized in biosynthetic compartments (rough ER and Golgi cisternae) of hepatocytes, suggesting that this HSPG is synthesized and deposited in the space of Disse by the hepatocyte. The anti-liver HSPG IgG also stained basement membranes of hepatic blood vessels and bile ducts as well as those of kidney and several other organs (heart, pancreas, and intestine). An antibody that recognizes the basement membrane HSPG found in the rat glomerular basement membrane did not precipitate the 150-300-kD rat liver HSPG. We conclude that the liver sinusoidal space of Disse contains a novel population of HSPG that differs in its overall size, its distribution and in the size of its core protein from other HSPG (i.e., membrane-intercalated HSPG) previously described in rat liver. It also differs in its core protein size from HSPG purified from other extracellular matrix sources. This population of HSPG appears to be a member of the basement membrane HSPG family.
Thèses sur le sujet "Irregular cell space"
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Trieu, Thanh Ngoan. « Open data and environment simulation : environmental and social simulation on distributed process systems based on irregular cell space ». Electronic Thesis or Diss., Brest, 2024. http://www.theses.fr/2024BRES0047.
Texte intégralRésumé :
La combinaison d’automates cellulaires (CA) et de systèmes distribués offre un moyen simple de modéliser les problèmes environnementaux et sociaux en divisant les zones d’intérêt en segments spatiales discrètes pour le calcul parallèle. L’évolution de l’état de chaque segment est divisée en étapes temporelles discrètes. Les divisions géographiques en tant qu’espace cellulaire irrégulier permettent de tirer parti des données ouvertes pour alimenter les systèmes de simulation. Les données sont analysées pour en déduire les règles de transition apportant des influences distribuées dans un quartier. Une étude de cas de modélisation de la propagation épidémique basée sur les divisions administratives est présentée. Étant donné l’hypothèse que l’épidémie se propage aux personnes vivant dans le quartier, un système de simulation est généré en fonction des voisins adjacents avec des conditions initiales de collecte à partir du portail de données ouvertes du gouvernement. Une approche hybride est introduite avec la coopération entre les tuiles régulières et les espaces cellulaires irréguliers dans la modélisation des activités côtières. Une simulation environnementale est nécessaire pour représenter les caractéristiques du sol et de la mer qui se propagent dans les deux espaces. Ces caractéristiques sont très différentes en raison de la capacité et de la réaction du sol, et du comportement de la mer, en particulier les courants et les marées. Le problème des marées vertes est modélisé lorsque les nutriments sont présents en concentrations élevées et piégés par les courants de maréeThe combination of Cellular automata (CA) and distributed systems provide a simple way to model environmental and social issues by dividing the relevant areas into discrete spatial segments for parallel computation. The state evolution of each segment is divided into discrete time steps. Geographic divisions as irregular cell space give a chance to take advantage of Open Data in feeding the simulation systems. Data are analyzed to deduce the transition rules bringing distributed influences in a neighborhood. A case study of epidemic propagation modeling based on geographic divisions is presented. Given an assumption that the epidemic is spreading to people living in the neighborhood, a simulation system is generated based on adjacent neighbors with initial conditions collected from the government open data portal. A hybrid approach is introduced with the cooperation between regular tiles and irregular cellspaces in modeling shore activities. Environmental simulation is needed to represent ground and sea characteristics modeling spreading occurring on both spaces. These characteristics are very different due to soil capability and reaction, and sea behavior, in particular currents and tides. The problem of green tides is modeled when nutrients arepresented in high concentrations and entrapped by tidal currents
Chapitres de livres sur le sujet "Irregular cell space"
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Saltzman, W. Mark. « Cell Adhesion ». Dans Tissue Engineering. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195141306.003.0011.
Texte intégralRésumé :
The external surface of the cell consists of a phospholipid bilayer which carries a carbohydrate-rich coat called the glycocalyx; ionizable groups within the glycocalyx, such as sialic acid (N-acetyl neuraminate), contribute a net negative charge to the cell surface. Many of the carbohydrates that form the glycocalyx are bound to membrane-associated proteins. Each of these components— phospholipid bilayer, carbohydrate-rich coat, membrane-associated protein—has distinct physicochemical characteristics and is abundant. Plasma membranes contain ∼50% protein, ∼45% lipid, and ∼5% carbohydrate by weight. Therefore, each component influences cell interactions with the external environment in important ways. Cells can become attached to surfaces. The surface of interest may be geometrically complex (for example, the surface of another cell, a virus, a fiber, or an irregular object), but this chapter will focus on adhesion between a cell and a planar surface. The consequences of cell–cell adhesion are considered further in Chapter 8 (Cell Aggregation and Tissue Equivalents) and Chapter 9 (Tissue Barriers to Molecular and Cellular Transport). The consequences of cell–substrate adhesion are considered further in Chapter 7 (Cell Migration) and Chapter 12 (Cell Interactions with Polymers). Since the growth and function of many tissue-derived cells required attachment and spreading on a solid substrate, the events surrounding cell adhesion are fundamentally important. In addition, the strength of cell adhesion is an important determinant of the rate of cell migration, the kinetics of cell–cell aggregation, and the magnitude of tissue barriers to cell and molecule transport. Cell adhesion is therefore a major consideration in the development of methods and materials for cell delivery, tissue engineering, and tissue regeneration. The most stable and versatile mechanism for cell adhesion involves the specific association of cell surface glycoproteins, called receptors, and complementary molecules in the extracellular space, called ligands. Ligands may exist freely in the extracellular space, they may be associated with the extracellular matrix, or they may be attached to the surface of another cell. Cell–cell adhesion can occur by homophilic binding of identical receptors on different cells, by heterophilic binding of a receptor to a ligand expressed on the surface of a different cell, or by association of two receptors with an intermediate linker. Cell–matrix adhesion usually occurs by heterophilic binding of a receptor to a ligand attached to an insoluble element of the extracellular matrix.
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Koch, Christof. « Synaptic Input ». Dans Biophysics of Computation. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195104912.003.0010.
Texte intégralRésumé :
How information circulates in the brain was the subject of a heated debate lasting a decade or more among anatomists in the closing years of the last century. One camp argued that neural tissue consisted of a continuum, a syncytium, with no discernible functional units while the opposing view held that the brain consisted of discrete units, the nerve cells, communicating through point-to-point contacts that Sherrington dubbed synapses. Although in principle both views can be supported, in practice the majority of rapid communication occurs via specific point-to-point contacts, at either chemical and electrical synapses. Ephaptic transmission refers to nonsynaptic, electrical interactions between neurons. While such interactions do occur, for instance, among adjacent, parallel axons across the extracellular space, they are, by their very nature, neither very strong among any one pair of processes nor very specific. Their functional significance—if any—is currently not known, and we will not discuss them here (Traub and Miles, 1991; Jefferys, 1995). In the beginning chapter, we introduced the action of fast, chemical synapses. Given their importance, we will now return to this topic in greater depth. We first overview the pertinent biophysical events underlying chemical synaptic transmission and some of the vital statistics of synapses before we come to the mathematical treatment of synaptic input. In the last section, we will summarize our knowledge of electrical synapses and their computational role. Most typically, a synapse consists of a presynaptic axonal terminal and a postsynaptic process that can be located on a dendritic spine, on the trunk of a dendrite, or on the cell body. Figure 4.1 shows some examples of synapses among cortical cells as seen through a high-powered electron microscope. It is not easy at first to identify the synapses amid all the curved, irregular, and densely packed structures making up the neuronal tissue. In a number of locations, such as the retina or the thalamus, a synaptic connection is made between two dendrites, rather than between an axon and a dendrite. These synapses are called dendrodendritic synapses; they are believed to be relatively rare in the adult cortex. Most synapses are small and highly specialized features of the nervous system. As we will see, a chemical synapse converts a presynaptic electrical signal into a chemical signal and back into a postsynaptic electrical signal.
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Koch, Christof. « Stochastic Models of Single Cells ». Dans Biophysics of Computation. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195104912.003.0021.
Texte intégralRésumé :
The majority of experiments in neurophysiology are based upon spike trains recorded from individual or multiple nerve cells. If all the action potentials are taken to be identical and only the times at which they are generated are considered, the experimentalist obtains a discrete series of time events {t1,···, tn}, where t¡ corresponds to the occurrence of the i th spike, characterizing the spike train. This spike train is transmitted down the axon to all of the target cells of the neuron, and it is this spike train that contains all of the relevant information that the cell is representing (assuming no dendro-dendritic connections). As alluded to in the preceding chapter, there are two opposing views of neuronal coding, with many interim shades. One view holds that it is the firing rate, averaged over a suitable temporal window (Eqs. 14.1 or 14.2), that is relevant for information processing. The dissenting view, correlation coding, argues that the interactions among spikes, at the single cell as well as between multiple cells, encodes information. A key property of spike trains is their seemingly stochastic or random nature, quite in contrast to switching in digital computers. This randomness is apparent in the highly irregular discharge pattern of a central neuron to a sensory stimulus whose details are rarely reproducible from one trial to the next. The apparent lack of reproducible spike patterns has been one of the principal arguments in favor of the hypothesis that neurons only care about the firing frequency averaged over very long time windows. Such a mean rate code is very robust to “sloppy” hardware but is also relatively inefficient in terms of transmitting the maximal amount of information per spike. Encoding information in the intervals between spikes is obviously much more efficient, in particular if correlated across multiple neurons. Such a scheme does place a premium on postsynaptic neurons that can somehow decode this information. Because little or no information can be encoded into a stream of regularly spaced action potentials, this raises the question of how variable neuronal firing really is.
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Stoian, Marilena. « SARCOIDOSIS AND ACUTE KIDNEY INJURY ». Dans Sarcoidosis - Diagnosis, Research, and Therapy of a Granulomatous Disease of Unknown Etiology [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.1002393.
Texte intégralRésumé :
Sarcoidosis is a multi-organ disease characterized by the formation of non-caseating epithelioid granulomas in many organs. The kidneys are not commonly affected but when the disease involves these organs. It is comprised of non-caseating granulomatous interstitial nephritis (GIN) and hypercalcemia-related disorders. In the latter case, acute kidney injury as initial presentation of the disease is a rare entity, and it is postulated to appear due to several pathogenic processes: (1) interstitial nephritis with or without granulomas, (2) nephrocalcinosis with or without nephrolithiasis, and (3) urethral obstruction. A 71-year-old man presented to the clinic with a history of lethargy, nausea, short memory loss and a 10 kg weight loss all of which appeared within the past 6 months. He was also known with prostate adenoma and was under the care of a urologist. Upon physical examination the following aspects were noted: blood pressure of 160/100 mmHg, heart rate 60 bpm and an irregular enlarged prostate. The chest X-ray was normal and blood samples revealed anemia, hypercalcemia, and increased values of urea and creatinine. An ultrasound of the kidneys was performed and no abnormalities were noted. The urinalysis showed the presence of protein +, glucose+, blood 2+, a few white cells and some granular casts. The next step was to perform a renal biopsy that revealed areas of lymphocytic tubulitis, mild mononuclear interstitial infiltrate, some non-necrotizing epithelioid granulomas comprised of Langerhans-type giant cells and epithelioid macrophages. Peri-tubular interstitial calcifications were also noted. As a result a histological diagnosis was summarized as acute or chronic granulomatous interstitial nephritis with nephrocalcinosis. A CT scan pf the chest was subsequently performed and it revealed calcified lymph nodes in the mediastinum involving the space between the aorta and the trachea and numerous nodules scattered bilateralally over the entire lung parenchyma with no apparent periseptal or perivascular association. These findings were diagnosed as sarcoidosis. The serum ACE level was found abnormal and therefore, a clinical diagnosis of sarcoidosis was made and the patient was started on 40 mg of oral prednisone daily with rapid improvement in the overall general condition. Sarcoidosis is an uncommon disease that should be suspected in front of a patient that presents with hypercalcemia and acute kidney injury. After excluding other causes of hypercalcemia such as multiple myeloma, primary hyperparathyroidism, and paraneoplastic phenomena, a renal biopsy is then indicated to confirm the diagnosis of sarcoidosis.
Actes de conférences sur le sujet "Irregular cell space"
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Choi, C. C. C., et S. H. K. Lee. « Fluid Flow Resistance in a Simple Cubic Packed Bed ». Dans ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81931.
Texte intégralRésumé :
Motivated by its frequent appearance in practical applications, scientists and engineers have been putting much efforts to pursue the ability to predict fluid flow behavior in sphere packed bed, in particular the fluid-solid interaction therein. The network model has recently been used to predict the fluid flow behavior in a sphere packed bed for a smaller length-scale domain of interest. The major questions for this approach are the representation of the irregular void space as a three dimensional network and the assignment of the flow resistance values. The application of Deluanay Cell to discretize the void space helps retain the geometrical and topological information without any empirical data fitting in. However, the calculation of the flow resistance within the Delaunay cell is still a question to be solved due to its highly irregular topology. The objective of this study is to solve for the flow resistance between the pores in a simple cubic retaining all the geometrical information. And then to correlate the flow resistance with different values of Reynolds number such that the application of network model could extend outside the creeping flow regime. The results has been validated against experimental correlation and then correlated with Reynolds number with a correlation factor larger than 0.9.
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Norte Pinto, Nuno, António Pais Antunes et Josep Roca Cladera. « Application of a cellular automata model to the metropolitan area of Barcelona ». Dans International Conference Virtual City and Territory. Barcelona : Centre de Política de Sòl i Valoracions, 2009. http://dx.doi.org/10.5821/ctv.7578.
Texte intégralRésumé :
Cellular Automata (CA) models are among the most popular models for simulating land use change/growth in urban areas around the world and have experienced a significant development over the last twenty years. These models have their origins on the efforts of devising mathematical rules for biological systems and for evolution developed by mathematicians von Neumann and Stanislaw Ulam in the 1940s. Two main
features made CA interesting for urban studies, to which they were introduced by Waldo Tobler in the early 1970s. First, their intrinsic spatiality, which is suitable for the simulation of a variety of geographic phenomena. Second, the possibility of simulating complex patterns of, for example, land use starting from
a simple conceptual framework that includes the definition of a cell space, a neighborhood, and a finite set of transition rules applied to a finite set of cell states. These models have been developed for different urban contexts and are mainly based on the use of regular cells derived from remote sensing imagery.
This is a simplification in the representation of urban areas: on the one hand, regular cells do not represent
common urban form and, on the other hand, they do not held information of any type other than land use, obtained from automatic classification.
These issues suggested the consideration of irregular cells linked to reliable information, that is, census blocks. Census blocks are drawn considering the form of urban areas and they are the most reliable
source of data on a wide variety of subjects, being a natural choice for the design of CA cells. We present in this paper an application of a CA model to simulate urban change in the Metropolitan Area of Barcelona, in a prospective analysis of 20 years. The model uses irregular cells designed considering census blocks.We describe the main features of the model and the calibration process, as well as the simulation results.
We also discuss some new features that are the core of our current research on CA.
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Jammoul, M., F. O. Alpak et M. F. Wheeler. « An Enriched Galerkin Discretization Scheme for Two Phase Flow on Non-Orthogonal Grids ». Dans SPE Reservoir Simulation Conference. SPE, 2023. http://dx.doi.org/10.2118/212238-ms.
Texte intégralRésumé :
Summary The representation of faults and fractures using cut-cell meshes often results in irregular non-orthogonal grids. Simple finite volume approaches fail to handle complex meshes because they are highly prone to grid orientation effects and only converges for K-orthogonal grids. Wide stencil approaches and higher order methods are computationally expensive and impractical to adopt in commercial reservoir simulators. In this work, we implement an Enriched Galerkin (EG) discretization for the flow and transport problems on non-orthogonal grids. The EG approximation space combines continuous and discontinuous Galerkin methods. The resulting solution lies in a richer space than the the two-point flux approximation (TPFA) method and allows a better flux approximation. It also resolves the inconsistencies that are usually associated with TPFA scheme. The method is tested for various non-orthogonal mesh configurations arising from different fault alignments. The performance of the scheme is also tested for reservoirs with strong anisotropy as well as reservoirs with heterogeneous material properties.
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Alifanov, Oleg M., Sergey A. Budnik, Aleksey V. Nenarokomov et Valery V. Cherepanov. « Mathematical Model of Heat Transfer in High-Porous Materials ». Dans 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22792.
Texte intégralRésumé :
The main purpose of this study was to confirm operability and effectiveness of the complex methods developed for theoretical prediction and experimental-computational determining some properties of modern highly porous materials, used as thermal protection shields in objects of space engineering, power engineering, etc. Them concern Fibrous Materials (FM), Open-Cell Reticulated Foams (OCRF) etc. The basis for the method proposed is in the combination of Direct Mathematical Simulation (DMS) for global structure of the complex irregular systems, which have the property of local regularity and Inverse Heat Transfer Problem (IHTP) methods. This approach makes possible to obtain and to predict such properties as radiation and molecular thermal conductivities, energy accommodation coefficient, complex refractive index, scattering indicatrix, scattering and absorption factors, etc. Such problems are of great practical importance in the study of material properties.
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Hagen, Øistein, Jørn Birknes-Berg, Ida Håøy Grue, Gunnar Lian, Kjersti Bruserud et Tone Vestbøstad. « Long-Term Area Statistics for Maximum Crest Height Under a Fixed Platform Deck ». Dans ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77263.
Texte intégralRésumé :
As offshore reservoirs are depleted, the seabed may subside. Furthermore, the extreme crests estimates are now commonly higher than obtained previously due to improved understanding of statistics of non-linear irregular waves. Consequently, bottom fixed installations which have previously had sufficient clearance between the deck and the sea surface may be in a situation where wave impact with the deck must be considered at relevant probability levels. In the present paper, we investigate the long-term area statistics for maximum crest height under a fixed platform deck for 2nd order short crested and long crested sea based on numerical simulations as a function of platform deck dimension for jackets. The results are for one location in the northern North Sea, but some key results are also reported and verified for a more benign southern North Sea location. Time domain simulations for long crested and short crested waves over a spatial domain with dimension of a platform deck are performed, and relevant statistics for airgap assessment determined. Second order waves are simulated for the different cells in the (Hs, Tp) scatter diagram for Torsethaugen two-peak wave spectrum for long-crested and short-crested sea. A total of 1000 3-hour sea states are generated per cell, and time series generated for 160 spatial points under a platform deck. Short-term and long-term statistics are established for the maximum crest height as function of platform dimension; inline and transverse to the wave direction, and over the area. Results are given for the linear sea and for the second order time series. The annual q-probability estimates for the maximum crest height over area as a function of platform dimension is determined for a location at the Norwegian Continental Shelf by weighting the short-term statistics for the individual cells in the scatter diagram with the long-term probability of occurrence of the sea state. To reduce the number of numerical second order simulations, the effect of excluding cells that have a negligible effect on the long term extreme crest estimate is discussed. The percentiles in the distribution of maximum crest (over area) in design sea states that corresponds to the extreme values obtained from the long-term analysis are determined for long crested and short crested sea. The increase in the extreme crest over an area compared to the point in space estimate is estimated for both linear and second order surface elevation.
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Kreuzer, Edwin, Eugen Solowjow, Gang Qiu, Thorben Hamann et Jürgen Grabe. « Leg-Seabed Interactions of Jack-Up Vessels due to Motions in Irregular Waves ». Dans ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24303.
Texte intégralRésumé :
This paper analyzes the leg-seabed interaction due to motions of a 3rd generation jack-up vessel in irregular waves. The proposed model considers hydrodynamic forces on the hull as well as on the legs. The sea floor reaction forces are analyzed with a Coupled Eulerian-Lagrangian (CEL) method. The results are used to develop a mechanical rheological model for the sea floor. With computational efficiency in mind a state-space representation in time domain is derived. The excitation of the system is caused by irregular waves, which are described by the JONSWAP spectrum. The proposed method allows the efficient computation of short term (2–15 min) scenarios and events through sampling of realizations. It is used to compute the impact forces on the legs from the seabed induced by irregular vessel motions. The presented framework is suitable for the planning of jack-up operations in the offshore wind industry. It can also be applied for the design of dynamic positioning and jacking systems.