Laminar Scheme Research Articles

Numerical investigation of wave-induced loads on an offshore monopile using a viscous and a potential-flow solver

Wave-induced loads on an offshore monopile were investigated using a viscous-flow solver and a potential-flow solver. Considered were only two steep regular wave trains, with the same height but different periods. The potential-flow approach relied on a weakly nonlinear time-domain solver (i.e., Green function). The viscous-flow solver used three solution schemes, namely, an Euler scheme that neglected the flow viscosity, a Laminar scheme that numerically integrated the full Navier–Stokes equations without a model accounting for the fluctuating portion of the velocity field, and a Reynolds-averaged Navier–Stokes scheme that modeled turbulent flow via a two-equation eddy-viscosity model. Numerical uncertainties of viscous-flow simulations were quantified, and computed results were validated against model test measurements. Overall, the main characteristics of wave-induced forces and bending moments were well predicted by all adopted numerical schemes. In terms of higher harmonic components, predictions only from the viscous-flow solver compared favorably to the experimental measurements, including the local free surface elevations, higher harmonic forces/moments, and the secondary wave load cycles. The effect of strong nonlinear motion of free surface on the wave-induced total loading was secondary, and the contribution from the associated viscous and turbulent effects was also very limited. Nevertheless, they attribute to the generation of higher harmonic forces/moments as well as the secondary load cycle. In addition, the effects of wave steepness on the global, first- and higher harmonic forces were addressed.

Towards a unified scheme of cortical lamination for primary visual cortex across primates: insights from NeuN and VGLUT2 immunoreactivity.

Primary visual cortex (V1) is clearly distinguishable from other cortical areas by its distinctive pattern of neocortical lamination across mammalian species. In some mammals, primates in particular, the layers of V1 are further divided into a number of sublayers based on their anatomical and functional characteristics. While these sublayers are easily recognizable across a range of primates, the exact number of divisions in each layer and their relative position within the depth of V1 has been inconsistently reported, largely due to conflicting schemes of nomenclature for the V1 layers. This conflict centers on the definition of layer 4 in primate V1, and the subdivisions of layer 4 that can be consistently identified across primate species. Brodmann’s (1909) laminar scheme for V1 delineates three subdivisions of layer 4 in primates, based on cellular morphology and geniculate inputs in anthropoid monkeys. In contrast, Hässler’s (1967) laminar scheme delineates a single layer 4 and multiple subdivisions of layer 3, based on comparisons of V1 lamination across the primate lineage. In order to clarify laminar divisions in primate visual cortex, we performed NeuN and VGLUT2 immunohistochemistry in V1 of chimpanzees, Old World macaque monkeys, New World squirrel, owl, and marmoset monkeys, prosimian galagos and mouse lemurs, and non-primate, but highly visual, tree shrews. By comparing the laminar divisions identified by each method across species, we find that Hässler’s (1967) laminar scheme for V1 provides a more consistent representation of neocortical layers across all primates, including humans, and facilitates comparisons of V1 lamination with non-primate species. These findings, along with many others, support the consistent use of Hässler’s laminar scheme in V1 research.

A confirmation of Rexed's laminar hypothesis using the Sholl linear method complemented by nonparametric statistics

Images of Golgi-impregnated neurons from laminae I to VI in the dorsal horn of the cat spinal cord were subjected to the linear Sholl analysis of concentric circles to support Rexed's hypothesis on the laminar organization of spinal gray matter in mammals. Since Rexed's determination of the laminae is based upon size, location, and grouping of cell bodies, neglecting one of the principal morphologic attributes of the neuron—the dendritic tree, the purpose of the present study was to evaluate Rexed's hypothesis testing the structure of dendritic arborization patterns of neurons. The differences in the complexity of dendritic trees between the groups of neurons from different laminae were evaluated by nonparametric statistics. Data obtained using Sholl's method is not always subjected to complete statistical analysis. The problem becomes particularly apparent in the quantitative examination of dendritic structures. Our aim was also to perform a careful analysis of our data for normality, in order to choose the appropriate statistical method for data processing. In the linear Sholl analysis, it is important to properly represent and interpret the frequency functions. The objective of this study was also to investigate the problems of determining the frequency functions, plotting the corresponding lines of regression, and measuring the degree of fluctuation of experimental data points around these lines. The main result of our testing is a confirmation of Rexed's laminar scheme: we have proved that there are 6 out of 10 possible pairs of samples where one member significantly differs from the other, i.e. one lamina is significantly distinguishable from the other.

Mathematical modeling and computational analysis of neuronal cell images: Application to dendritic arborization of Golgi-impregnated neurons in dorsal horns of the rat spinal cord

Neurons of the rat spinal cord have been stained using the Golgi impregnation method. Successfully impregnated neurons from laminae I to VI were subjected to a computational analysis for complexity of dendritic tree structure. The analysis was performed using ruler-counting and circle-counting techniques. Our analysis aimed to support quantitatively the general concept of Rexed's laminar scheme of the dorsal horn of mammals. For that purpose, we have developed two mathematical models of neuronal arborization patterns, whose solutions yielded the inverse power-law and generalized power-law scaling. The latter comprises two main parameters: (i) the anfractuosity, characterizing the degree of dendritic complexity and (ii) an estimate of the total length of arbor dendrites. The anfractuosity can distinguish among the sets of drawings over all six laminae.

Fractal analysis of the laminar organization of spinal cord neurons

Images of Golgi impregnated neurons from different laminae of the human and rat dorsal horns were subjected to a quantitative analysis to support the Rexed's laminar scheme in mammals. Four methods of fractal analysis were performed in the proceedings: box-counting, mass-radius, cumulative intersection, and vectorized intersection. The results show that the box-counting method is more precise than the other fractal methods performed, and offers support for the conclusion that fractal analysis can successfully discriminate the neuron populations among different laminae. The analysis supports the concept of Rexed's cytoarchitectonic lamination of the dorsal horn.

Numerical analysis of a cross-flow compact heat exchanger for vehicle applications

A numerical thermo-fluid–dynamic study of a compact crossed flows heat exchanger (HX), used to cool the high-pressure oil used in hydraulic circuits of earth-movement industrial vehicles, was performed. The numerical analysis was carried out to verify the influence of the hydrodynamic regimes of the fluids involved in the heat transfer process, induced by fins in the channels, on the performances of the whole HX. The analysis was developed through three steps of increasing complexity. After a simple model built to evaluate the consistent boundary conditions of temperature, a small scale analysis of the fluid–dynamic phenomena inside the HX was carried out, taking into account geometrical periodical units at oil (OS) and at air side (AS). With the results obtained in this way, the HX performances were evaluated on an overall scale, extrapolating the data up to the real dimensions in terms of heat transfer and pressure loss. With the “small scale” approach at the OS the local heat flux and the pressure losses were quantified, using a laminar scheme and a high detail in the geometry description of the turbulence generators. With the “full scale” approach, then, simulations were performed considering a porous media with characteristics set up on the previous analysis. The global heat transfer coefficient and the pressure losses were so accounted for. At the AS, the schematization was limited to two periodic portions of the flow and results allowed to evaluate both local and overall heat transfer coefficients. Results were again extrapolated to the real dimensions of the channels. The results come out from the AS detailed analysis were, then, related to the output of the ones at OS. This was done to obtain crossed confirmations of the overall results in terms of thermo-fluid–dynamic performances of the HX at design conditions.

Cytoarchitectonic organization of the spinal cord in the rat: II. The cervical and upper thoracic cord.

A laminar cytoarchitectonic scheme of the cervical and upper thoracic segments of the rat spinal cord is presented in which Rexed's principles for the cat are applied. The material examined in the current investigation consists of 50-80 microns-thick unstained or Nissl-stained sections, and 2 microns-thick plastic-embedded sections stained with paraphenylenediamine. The cytoarchitectonic organization was found to be basically similar to that of the cat. As in our previous study of the cytoarchitectonic organization of the lower thoracic and lumbosacral spinal cord (Molander et al.; J. Comp. Neurol. 230:133-141, '84), the borderlines between the laminae were often found to be ambiguous, suggestive of zones of transition rather than sharp borders. In addition to the laminar scheme, the distribution of certain important cell groups, including the column of Clarke, the central cervical nucleus, the lateral cervical nucleus, the lateral spinal nucleus, and the internal basilar nucleus, is described.

The cytoarchitectonic organization of the spinal cord in the rat. I. The lower thoracic and lumbosacral cord.

A laminar cytoarchitectonic scheme of the lower thoracic and lumbosacral segments of the rat spinal cord is presented in which Rexed's principles for the cat are applied. The material consists of 80-micron-thick sections stained with toluidine blue or according to van Gieson and 2-micron-thick sections stained with p-phenylenediamine or toluidine blue. The cytoarchitectonic organization of the rat spinal cord was found to be basically similar to that of the cat, although certain differences exist--for example, in the extension of the laminae. In addition to the laminar scheme, the distribution of certain cell groups, Lissauer's tract, and the pyramidal tract were investigated.

The dendritic organization of the human spinal cord: The dorsal horn

The human spinal cord was studied with the Golgi method from 26 weeks gestational age onto adult life. Impregnated neurons were analyzed morphometrically by an adaptation of Sholl's concentric circle method in order to specify dendritic geometry, ramification richness and branching pattern. Neurons were classified according to Rexed's laminar scheme, identified on adjacent Nisslstained sections. The following features were found to be characteristic of the dorsal horn laminae. Lamina I is formed of a uniform population of large, poorly ramified neurons. Their main dendritic domaine is disk-shaped in the tangential plane with a mean diameter of about 800 μm. Orthogonal, spiny dendrites penetrating into lamina II are numerous even in adult material. Four cell types, all lying in the sagittal plane, are found in lamina II. (1) ‘Islet cells’ (about 30% of impregnated neurons) have a rostrocaudal, cylindrical dendritic domaine with a long axis of± 600 μm, a few scattered spines and a richly branched axonal network, confined to the dendritic territory. They are more numerous in the central part of lamina II. A few islet cells have two axons. (2) ‘Filamentous cells’ (about 20%), so called because of their multiple filiform, spiny dendrites, are vertico-sagittally oriented. Their soma is located in inner or outer lamina II, their dendritic tree, a trapezoïd of about 280 μm in height, being dorsal or ventral. The axon emits some collaterals in the vicinity of the dendritic tree, then it penetrates into lamina I or Lissauer's tract. (3) ‘Curly cells’ (about 10%) have a complex, twisted, spine-rich dendritic tree. The dendritic domaine can be schematized by a sagittal disk with a diameter of about 200 μm, the cell body being eccentric. Curly cells are mainly found in outer lamina II. Their axon penetrates into lamina I or Lissauer's tract. (4) ‘Stellate cells’ (about 40%) are multipolar neurons preferentially found in inner lamina II. They have straight, spine-poor dendrites, which cover a large (longest diameter ca. 500 μm), elliptical territory extending into laminae I and III. Their axon gives longitudinal collaterals to lamina II before penetrating deeply into laminae III and IV. Lamina III contains a mixed population of ‘antenna-like neurons’ with a vertical, cone-shaped dendritic domaine and ‘radiate cells’ characterized by a small, spherical territory. All lamina IV neurons are medium or large sized ‘antenna-like neurons’ whose dorsally oriented, cone-shaped dendritic domaine may have a height of 1000 μm. It can be concluded that the dorsal horn of the human spinal cord has several distinct dendroarchitectonic features, different from those reported in animals. The possible functional implication of some dendritic features is examined and a laminar dendroarchitectonic scheme of the human cord is proposed as a morphological tool for future neuroanatomical and neuropathological studies.

Rexed's laminar scheme as it applies to the rat cervical spinal cord

Rexed's laminar scheme as it applies to the rat cervical spinal cord