Interconnected Capillaries Research Articles

Angiolipoma of the Female Breast: Clinicomorphological Correlation of 52 Cases

The authors analyzed 52 cases of female breast angiolipoma (AL). Age distribution was 25 to 80 years of age (56.81 ± 12.78). Most cases showed vascularity below 50%, and 14 cases had vascularity >50%. Cellular and low-vascularity ALs had different clinical and radiological presentations. The mean size was 7.00 ± 3.62 mm for cellular ALs and 19.61 ± 7.58 mm for low-vascularity ALs. In any paucicellular area, the authors could identify a cluster of at least 3 interconnected vessels. The endothelium was mostly flat with uniform, hyperchromatic nuclei, and mitoses and nucleoli were absent. Fibrin thrombi in proliferating capillaries were noted in 96% of cases. Low-vascularity AL can be reliably distinguished on needle core biopsy from other lipomatous and vascular tumors of the breast. Tortuosity and proliferation of capillaries with at least 3 interconnected capillary channels in 1 focus with associated fibrin thrombi constitute a very strong clue for the diagnosis of AL on a breast needle core biopsy. Definite diagnosis of cellular AL is not always feasible because of rare cases with mitotic activity and cellular atypia. Excision is often recommended for cellular AL.

Effects of solvent treatments on characteristics of superporous hydrogels

The synthesis of an acrylamide-based superporous hydrogels (SPHs) was carried out by solution polymerization. SPHs were submerged in one of the organic solvents: diethyl ether, acetone, absolute ethanol, or hexane for 48 h. The characterization studies were performed by measurement of apparent density, porosity, swelling, mechanical strength, and scanning electron microscopy (SEM). The swelling ratio was calculated based on the mass of SPHs in the swollen state and in the dried state. The penetration pressure of the SPHs was measured from the force required for complete fracture of SPH. SPHs showed porosities of more than 60%. In double distilled water SPHs showed tremendous increase in equilibrium swelling capacity. But, when the same SPHs were placed in artificial gastric fluid for swelling, they showed very low equilibrium swelling capacity. The solvent treated SPHs showed good swelling characteristics in both the swelling media compared to that of SPH without solvent treatment. When an artificial gastric fluid was used as a swelling medium, ethanol- and hexane-treated SPHs showed higher penetration pressure compared to SPH without solvent treatment, while diethyl ether- and acetone-treated SPHs showed less penetration pressure. SEM images clearly indicate the formation of interconnected pore and capillary channels. The characterization studies revealed that the SPHs treated with solvents showed remarkable effects on their characteristics compared to SPH without solvent treatment. The results of the present study provide background for the selection of solvent for SPH treatment to improve characteristics that will lead to modification of the available SPH-based gastric retention devices. Keywords: superporous hydrogel, solvent, scanning electron microscopy, swelling, penetration pressure

Transient Liquid Phase Bonding of 2D Fiber Reinforced Carbon-Carbon Composites

2D Fiber Reinforced carbon-carbon composites (C/C) was successfully bonded to itself with Ti-Ni-Ti sandwich interlayer by transient liquid phase bonding at 1050°C for 20~100 min under axial pressure of 0.1 MPa. The microstructures of joints were investigated and bonding strengths were examined, fracture surfaces were characterized by SEM and XRD. The results show that Ti-Ni eutectic liquid infiltrates into the interconnected capillaries of C/C through the open pores of the C/C boding surface. The presents of the breakpoints in joint alloy and the reaction between Ti and C are beneficial to the improvement of bonding strength. The shear strength of joint is as high as 37.4 MPa.

Leukocyte Margination in Alveolar Capillaries: Interrelationship with Functional Capillary Geometry and Microhemodynamics

The pulmonary capillary microvasculature harbors a large pool of intravascularly marginated leukocytes. In this study, we investigated the interrelationship of leukocyte margination with characteristics of functional capillary geometry and microhemodynamics in alveolar capillary networks. In 22 anesthetized rabbits we assessed functional capillary density, average capillary length, red blood cell velocity and leukocyte kinetics in alveolar capillary networks in vivo by intravital fluorescence microscopy. In alveolar wall areas of 12,800 ± 1,800 μm², we detected 3.6 ± 0.5 sticking leukocytes and 21.0 ± 1.9 functional capillary segments with an average capillary length of 35.7 ± 2.1 μm. We calculated that approximately 15% of functional capillary segments are blocked by marginated leukocytes. Leukocyte margination was predominantly observed in capillary networks characterized by a high functional capillary density, short capillary segments and low red blood cell velocities. The multitude of interconnected capillary channels in these networks may allow alveolar blood flow to bypass marginated leukocytes. Hence, this interrelationship may be relevant for maintenance of adequate alveolar perfusion and low capillary network resistance despite excessive leukocyte margination in the pulmonary microvasculature. Local microhemodynamic factors may play a regulatory role in the spatial distribution of leukocyte margination.

THE EFFECTS OF MEDIUM THICKNESS ON THE ISLAND SIZE DISTRIBUTION IN IMMISCIBLE DISPLACEMENT FLOW IN POROUS MEDIA

Abstract The invasion percolation algorithm is used to simulate two-fluid immiscible displacement of a wetting fluid by a non-wetting fluid in various porous media represented by two-dimensional and three-dimensional networks of interconnected capillaries. Trapping of the displaced fluid occurs, thereby creating isolated islands. The effects of the thickness of the porous medium on the island size distribution are studied for capillary displacements for the case in which buoyancy effects are negligible. It was found in a previous study that the number of islands of size s scales approximately as s~ in two-dimensional porous media, where a is a function of the fluid viscosity ratio. The present work reveals that there is a cross-over behavior between the two-dimensional and the three-dimensional problems.

A scanning electron microscopic study of the vascular sysdem of the bovine hind limb claw

The vascular organisation of the hind limb claws of clinically normal cattle was studied using scanning electron micrographs of plastic corrosion casts. The microvasculature of the dermal papillae and lamellae was demonstrated. A consistent vascular pattern was observed in the dermal papillae of the periople, coronary margin, sole and bulb. Ultrastructurally, the papillar vasculature consisted of a central artery and vein surrounded by a fine network of interconnected capillaries and venules. Arteriovenous anastomoses, connecting the central artery and vein, and peripherally situated arteriovenous loops were recognised in the terminal papillae of the white zone only. Arteriovenous anastomoses, focal enlargements and distension of the capillary bed were located within the interior half of the dermal lamellae. Numerous arteriovenous anastomoses were present throughout the entire dermis of the claw and were situated predominantly at the base of the dermal papillae and lamellae. The anastomoses and focal capillary enlargements may influence the blood flow in normal conditions and may play a significant role in the pathophysiology of bovine laminitis and sole ulceration.

The effects of capillary forces on the island size distribution in two-fluid immiscible displacement flow in porous media

A stochastic algorithm is used to simulate the immiscible displacement of a wetting fluid by a non-wetting fluid in a porous medium represented by a two-dimensional network of interconnected capillaries. As the interface advances trapping of the displaced fluid occurs thereby creating isolated islands of the displaced fluid. The number of islands of size s is found to scale approximately as s- alpha , where alpha depends on the capillary number and the viscosity ratio. The effects of capillary forces on the island size distribution are also studied.

Numerical models and experiments on immiscible displacements in porous media

Immiscible displacements in porous media with both capillary and viscous effects can be characterized by two dimensionless numbers, the capillary number C, which is the ratio of viscous forces to capillary forces, and the ratio M of the two viscosities. For certain values of these numbers, either viscous or capillary forces dominate and displacement takes one of the basic forms: (a) viscous fingering, (b) capillary fingering or (c) stable displacement. We present a study in the simple case of injection of a non-wetting fluid into a two-dimensional porous medium made of interconnected capillaries. The first part of this paper presents the results of network simulators (100 × 100 and 25 × 25 pores) based on the physical rules of the displacement at the pore scale. The second part describes a series of experiments performed in transparent etched networks. Both the computer simulations and the experiments cover a range of several decades in C and M. They clearly show the existence of the three basic domains (capillary fingering, viscous fingering and stable displacement) within which the patterns remain unchanged. The domains of validity of the three different basic mechanisms are mapped onto the plane with axes C and M, and this mapping represents the ‘phase-diagram’ for drainage. In the final section we present three statistical models (percolation, diffusion-limited aggregation (DLA) and anti-DLA) which can be used for describing the three ‘basic’ domains of the phase-diagram.

Microcirculation of the Coronary Band of the Equine Hoof

Scanning-electron-microscopic examination of corrosion casts was used to investigate the microcirculation of the coronary border of the equine hoof. Numerous peg-shaped capillary plexuses derived from arterioles extended distally from the dorsal branches of the digital arteries parallel to the hoof wall. The plexuses varied in length and consisted of a fine network of interconnected capillaries that converged to join a centrally situated venule. These centrally situated venules within the papillary plexuses gave rise to a vast venous plexus deep to the coronary band.

Pattern growth and fluid displacements through porous media

A review is given of various mechanisms which occur during immiscible displacements in 2-dimensional networks of interconnected capillaries. We show how the physical laws governing meniscus equilibrium and flow conditions lead to different statistical models (mean field, percolation, DLA…).

Geoelectrical and geohydrological precursors of earthquakes in northeastern India

Resistivity, S.P., earth current, spring discharge, chargeability, magnetic, water level in dug wells and microearthquake measurements were carried out at a site in a reserved forest area near Shillong from February to July, 1980 to make a preliminary assessment of the precursors of earthquakes in northeastern India. At the site, steeply dipping quartzites are exposed, which are characterised by abnormally high self-potential (−1900 mV) and high resistivity. It was observed that the earthquakes having magnitudes from 4 to 5 on the Richter scale with epicenters located at distances varying from 40 to 400 km from the site were preceded by significant variation in the geoelectrical and geohydrological parameters of rocks over a period of 7—20 days. The variation of resistivities of rocks as related to earthquakes was considered to be very interesting. These values gradually decreased by 25%, in some cases, and then gradually increased to attain the pre-anomaly level. Significant earthquakes were observed to occur when the resistivity values approached the normal level. It is envisaged that under influence of tremendous stresses at the hypocenters of earthquakes, the normal field of stress at the site of measurements was disturbed, which brought about two types of changes in fractured rocks. Firstly, the sturcture of the interconnected capillaries was deformed resulting in changes of electromechanical potential. Secondly, the porosity fraction of rocks changed. Slight changes in the porosity fraction of rocks resulted in considerable changes in the resistivity of rocks, as the formation factor was high. This work has shown that the resistivity of rocks may decrease or increase depending on the structural features of rocks and changes in field of stress. It has also been shown that the maximum change of resistivity value is proportional to the distances of hypocenters of earthquakes.

‘Seamless’ Endothelia within Fenestrated Capillaries of Duodenal Villi (Rat)

In a 3-dimensional reconstruction of the vascular system of a duodenal villus of rat, special endothelia which lack the interendothelial contacts (seamless endothelia) have been studied. They are perforated by the lumen instead of wrapping it. They only occur in the interconnected small capillaries while they are lacking in the main loops. This distribution may be due to the way in which these special endothelia develop.