Tortuous Channels Research Articles

Self-assembly of amorphous biophotonic nanostructures by phase separation

Some of the most vivid colors in the animal kingdom are created not by pigments, but by wavelength-selective scattering of light from nanostructures. Here we investigate quasi-ordered nanostructures of avian feather barbs which produce vivid non-iridescent colors. These β-keratin and air nanostructures are found in two basic morphologies: tortuous channels and amorphous packings of spheres. Each class of nanostructure is isotropic and has a pronounced characteristic length scale of variation in composition. These local structural correlations lead to strong backscattering over a narrow range of optical frequencies and little variation with angle of incidence. Such optical properties play important roles in social and sexual communication. To be effective, birds need to precisely control the development of these nanoscale structures, yet little is known about how they grow. We hypothesize that multiple lineages of birds have convergently evolved to exploit phase separation and kinetic arrest to self-assemble spongy color-producing nanostructures in feather barbs. Observed avian nanostructures are strikingly similar to those self-assembled during the phase separation of fluid mixtures; the channel and sphere morphologies are characteristic of phase separation by spinodal decomposition and nucleation and growth, respectively. These unstable structures are locked-in by the kinetic arrest of the β-keratin matrix, likely through the entanglement or cross-linking of supermolecular β-keratin fibers. Using the power of self-assembly, birds can robustly realize a diverse range of nanoscopic morphologies with relatively small physical and chemical changes during feather development.

Exencephaly in a live, full term fetus

Sir, Exencephaly is a rare malformation of the neural tube with a large amount of protruding brain tissue and absence of calvarium. It is considered to be an embryological precursor of anencephaly where the facial structures and the base of brain are always present. Most cases are stillborn. We report a case of Exencephaly in a live full term fetus which succumbed after 3 hours. A 21 yr old gravid, primipara was admitted with a history of post maturity. Ultrasound of the abdomen revealed a single live fetus with breech presentation and a suspicion of anencephaly. She was given a trial labour with no response. Hence an elective caesarean section was performed. Intra-operatively minimal liquor was detected and the presentation was complete breech. The female infant was 3kgs in weight and had an APGAR score of 6 to 8. The infant expired after 3 hours. At autopsy the fetal skull vault was absent and the brain was covered by a thick membrane with visible tortuous blood vessels [Figure 1]. Three other swellings were noted in the occipital region, one extending up to the cervical vertebrae [Figure 2]. The fetus had a normal forehead and the eyes were protruding. The ears, oral cavity and nasal cavity were normal. No other external anomalies were seen [Figure 3]. Figure 1 Cerebrum covered by highly vascularized tissue Figure 2 Three occipital masses composed of cerebellar tissue Figure 3 Exencephalic fetus with protruding eyeballs and no other external anomalies Internal autopsy showed the brain and overlying tissue being covered by a highly vascular layer below which was a layer of loose connective tissue 2 to 4 cms thick [Figure 1]. When this layer was removed, two roughly symmetrical cerebral hemispheres were seen. In the cerebral cortex the gyri were flattened, sulci were shallower and all surfaces were highly vascular. Cut sections of the cerebrum showed a single large ventricular chamber lined by numerous multi lobular soft tissue masses with a vague corpus callosum like white area. The average cortical thickness of the cerebrum was 2cms. The occipital nodules also showed similar findings. All thoracic and abdominal organs were normal and well formed. Lungs floatation test was positive. On microscopic examination, the layer between the cortical surface and meninges was composed of loose connective tissue containing numerous tortuous vascular channels and focal nodules of dysplastic neural elements. The cerebral tissue contained scattered neurons, neuroblasts and glial elements with a thinned out layer of cortical tissue. The nodules in the occipital region showed cerebellar tissue composed of nodules of dysplastic neural elements and was also covered by a highly vascular layer. Spinal subarachnoid space also showed foci of dysplastic neural tissue. Exencephaly is characterized by the absence of cranial cavity and scalp with a large amount of protruding brain tissue covered by a membrane, and with prominent bulging eyeballs. Exencephaly is considered to lie somewhere on the spectrum between anencephaly and encephalocoele.[1 2] It is much less common than anencephaly but it has the same etiology and recurrence risk as other neural tube defects.[3] Exencephaly is an uncommon malformation of the cranium that characteristically involves a large disorganized mass of brain tissue. The flat bones of calvaria are absent and the brain mass is left uncovered .It is a clinical entity which is incompatible with life.1Neural tube defects account for most CNS malformations. Failure of a portion of neural tube to close or reopening of a region of the tube after successful closure, may lead to one of the several deformities. In our case the primary diagnosis of anencephaly was ruled out on the basis that the flat bones of calvarium were absent. The marked dysplasia and disorganized development of cerebrum were atypical of meningoencephalocoele.[3] Exencephaly is rarely reported in human embryos. Anencephaly occurs in 1 in 5 per 1000 live births, more commonly in females.[4] It is thought to develop at 28 wks of gestation. As with anencephaly, exencephaly is also incompatible with life.[1 2] Forebrain development is disrupted and all that remains is the area cerebrovasculosa with a flattened remnant of disorganized brain tissue admixed with ependymal, choroid plexus and meningothelial cells.[4] Exencephaly is a rare precursor of anencephaly in which a large amount of brain tissue is present despite the absence of the calvaria. The brain in these cases consist of a disorganized, anarchic outgrowth of nervous tissue with polymicrogyria and nodules of heterotopias. In our case all the macroscopic and microscopic findings were as described in literature, although we could not explain the persistence of exencephaly late in pregnancy and survival of the fetus for 3 hours.

Influence of channel tortuosity on the lightning return stroke electromagnetic field in the time domain

The effect of lightning channel tortuosity on the associated electromagnetic (EM) fields in the time domain is investigated quantitatively from a new point of view. Due to the vanishing of geometric symmetry when taking into account the tortuosity of lightning channels, it is necessary to calculate the associated EM fields in the Cartesian coordinate system. An efficient technique is adopted to produce tortuous lightning channels and then the fractal dimension of the channel is calculated automatically by a program. The results show that at close distances, the dependence of EM fields on azimuth is significant, the ratio of MF peaks at two coaxial points with the channel base may reach about 4 and that of the EF may be larger than 2. With increased distance, the dependence of waveform on azimuth weakens. At distances of 10 km and 100 km, the current peaks derived from the EF peaks show good consistency with the current peak adopted, with an uncertainty less than 25%.

Numerical simulations for the effects of normal loading on particle transport in rock fractures during shear

Fluid flow and tracer transport in a single rock fracture during shear is investigated using the finite element method (FEM) and streamline particle tracking, considering evolutions of aperture and transmissivity with shear displacement histories under different normal stresses, based on laboratory tests. The distributions of fracture aperture and its evolution during shear were calculated from the initial aperture fields, based on the laser-scanned surface roughness of feature replicas of rock fracture specimens, and shear dilations measured during the coupled shear-flow tests in laboratory. The coupled shear-flow tests were performed under two levels of constant normal loading (CNL). A special algorithm for treating the contact areas as zero-aperture elements was used to produce more accurate flow field simulations using FEM. The simulation results agreed well with the flow rate data obtained from the laboratory tests, showing complex histories of fracture aperture and tortuous flow channels with changing normal stresses and increasing shear displacements for the flow parallel with the shear direction. A greater increase was observed for flow in the direction perpendicular to the shear direction, due to the significant flow channels created by the shearing process. From the obtained flow velocity fields, particle transport was predicted using a streamline particle tracking method with the flow velocity fields (vectors) taken from the flow simulations, yielding particle travel times, breakthrough curves, and the Péclet number, Pe. The transport behavior in the fracture is also anisotropic, and advective transport is greater in the direction parallel with the shear direction. The effect of normal stress on the particle transport is significant, and dispersion becomes larger with increasing normal stress.

Development of Carbon Coatings for Cordierite Foams: An Alternative to Cordierite Honeycombs

Cordierite foams were prepared by replication of polyurethane foams and were coated with three types of carbon xerogels. The dip coating and synthesis conditions were optimized, and the coated foams were characterized exhaustively. The composition of the starting solution, coat loading, and carbonization temperature are the most important parameters determining both textural and mechanical properties. Carbon xerogel coatings obtained from aqueous solutions of resorcinol (R) and formaldehyde (F) are macro-, meso-, and microporous but present the greatest shrinkage, which causes a loss of adhesion between ceramic foams and carbon coatings. The coatings from polyfurfuryl alcohol (PFA) and RF-poly(vinyl butyral) (Butvar) resin are highly microporous and present very good adhesion even after carbonization. In all cases, coatings induce the improvement of the mechanical properties, which is related to the fact that the coating fills the defects present in the cordierite foams, thereby affecting both the rigidity and the way cracks propagate through the coated samples. These materials, due to the synergetic role of the highly porous coatings and the tortuous channels of the ceramic foams, are suitable materials for adsorption or catalytic treatments of fluids.

Magnetorheological Bypass Damper Exploiting Flow Through a Porous Channel

A magnetorheological (MR) damper with a bypass valve containing porous media is developed. Movement of the piston forces MR fluid to flow from one side of the piston to the other, through an externally mounted bypass packed with magnetic spheres. The passageways between the spheres provide narrow, tortuous channels that act as a controllable valve when subjected to a magnetic field. A stationary magnetic coil is wrapped around the so-called porous valve, which is isolated from the MR fluid and external to the primary hydraulic cylinder. While flowing through the tortuous channels in the porous media created by the packed spheres, the MR fluid experiences varied local flow directions, and thus an external field can be applied in any direction to adjust damping levels. Additionally, the use of long channels, which are tightly packed to create narrow passageways, allows a very high damping force to be generated by a relatively compact damper. Furthermore, use of an externally mounted coil allows for maintenance accessibility, and the magnetic flux return path can be either empty (air) or any high permeability material. The damper is tested for steady-state sinusoidal displacements, and equivalent viscous damping and complex stiffness are computed. It is shown that the porous bypass valve MR damper can provide high controllable damping force and a wide force range.

Vascular anomalies

Vascular anomalies

Disordered mesoporous silica low- k thin films prepared by vapor deposition into a triblock copolymer template film

Mesoporous silica films have been prepared by a vapor phase method using tetraethoxysilane (TEOS) in a batch reactor and in a continuous flow reactor. The TEOS molecules penetrated into a triblock copolymer films and then a triblock copolymer/silica composite structure was formed. A two dimensional grazing-incidence small angle X-ray scattering pattern and field emission scanning electron microscopy images of the films indicated that the films possess ordered and disordered regions. The tortuous pore channels in the wormhole-like disordered structure run parallel to the film surface. The mesostructured triblock copolymer/silica composite films were treated with a trimethylethoxysilane (TMES) vapor before and after calcination. The vapor infiltration treatments effectively improved mechanical strength and hydrothermal stability of the films. The dielectric constant of the TMES-treated mesoporous silica films was reduced into the 1.5–1.7 range.

A Volcanic Reservoir: Integrated Facies Distribution Modeling and History Matching of a Complex Pressure System

Summary A Tcf-class gas field has been producing over several decades in Japan. The reservoir body comprises stacked rhyolite lava domes erupted in a submarine environment. A porous network developed in each dome and rapid chilling on contact with seawater caused hyaloclastite to be deposited over it. Although hyaloclastite is also porous in this field, its permeability has been reduced dramatically by the presence of clay minerals. Impermeable basaltic sheets and mudstone seams are also present. Each facies plays a specific role in the pressure system. Stratigraphic correlation originally identified multiple reservoirs. Gas has been produced almost exclusively from the largest one. However, following 10 to 20 years of production, the pressures within unexploited reservoirs were noticed to have declined at a variety of rates. Unusual localized behavior has also been observed. Because seismic data were not proved particularly informative, we decided to remodel the entire system by specifically using pressure data. We employed a combination of multipoint geostatistics and probability perturbation theories. This approach successfully captured the curved facies boundaries within stacked lava domes while accounting for pressure data by means of history matching to address nonstationarity in the real field. Building a suitable training image is commonly a difficult aspect of multipoint methods and poses particular problems for volcanic reservoirs. It was accomplished here by iteratively adjusting the prototype until satisfactory history matching was achieved with a reasonable number of perturbations. Ambiguous reservoir boundaries were represented stochastically by populating a predetermined model space with pay and nonpay pixels. The modeling results closely simulate measured pressure histories and appear realistic in terms of both facies distributions and reservoir boundaries. They suggest that uneven pressure declines between different units are caused by the tortuous flow channels that connect them. The results also account for the unusual smaller-scale pressure performances observed. The final training image obtained here indicates more intensive spatial variations in facies than previously appreciated. Original gas in place (OGIP) estimates made with 20 equiprobable realizations are scattered within ±15% of the mean value. Estimates of incremental recovery made by drilling a step-out well reveal greater variation than those made by installing a booster compressor, which quantifies a higher associated geological risk.

Growth history of a diffusely venting sulfide structure from the Juan de Fuca Ridge: A petrological and geochemical study

Centimeter‐scale mineralogical and chemical analyses of a diffusely venting, ∼280°C sulfide structure (called Roane) from the Mothra Hydrothermal Field on the Juan de Fuca Ridge reveal a complex growth history. These analyses document four well‐defined zones, which from the exterior to the interior of the structure include a barite‐silica zone (Fossil Worm Tube Zone), a silica‐sulfide zone (Silica Zone), a sulfide‐silica zone (Outer Sulfide Zone), and a sulfide ± gordaite ± silica zone (Inner Sulfide Zone). These features are a product of a myriad of processes that include extensive mineral replacement, ingress of seawater, fracturing and breakout of hot hydrothermal fluids, significant conductive cooling, and the sustained, broad‐scale outflow of warm fluids from the walls through a porous and permeable matrix. Roane lacks an open, throughgoing, chalcopyrite‐lined, central conduit. Instead, it hosts an anastomosing, discontinuous network of tortuous channels within the interior of a sponge‐like matrix of amorphous silica, sulfide, sulfate, and clay minerals. Megafaunal communities at the summit and sides of this mature, diffusely venting chimney provide a constructional framework for new growth. Isolation of hydrothermal fluid from seawater during progressive fossilization of megafauna and the early formation of barite‐silica assemblages promote flow of higher‐temperature fluids within the interior. Continued isolation of interior higher‐temperature fluids, through increased mineral precipitation and expansion of the structure, leads to a Zn sulfide + pyrite‐dominated permeable matrix and a network of tortuous channels that form a central porous conduit. This conduit is shielded by a weakly silicified, metal sulfide inner wall and a strongly silicified outer wall. The most outer portions of the walls are highly porous and sites of significant advection and mixing between hydrothermal fluids and seawater. The mineralogy and chemistry of Roane are strongly affected by ammonia‐ammonium buffering of the pH during cooling of the hydrothermal fluids. The two major results of the buffering are (1) precipitation of Zn sulfide at higher temperatures than are typical for bare‐rock systems, leading to the correlation of Cu, Zn, Cd, and Se and (2) increased deposition of amorphous silica and clay minerals.

Downscaling Equal Channel Angular Pressing

ECAP (equal channel angular pressing) is a well-known severe plastic deformation method used to produce ultra-fine grained materials. The dimensions of ECAP specimens are usually in the centimeter range. For producing high strength wires or fibres with diameter in the micrometer/millimeter range, downscaling of the ECAP process may be a viable option. To achieve this, several experiments were carried out. For downscaling to the micrometer range, porous steel discs can be used as processing tools. In this case, a solid state infiltration method as a variant of the forcefill process can be used. Extremely large strain is introduced due to the material flow through the tortuous channels inside a porous pre-form leading to grain refinement depending on processing conditions. To obtain specimens with a typical dimension in the millimeter range, the forcefill approach was altered by using die channels produced by conventional drilling. The tool geometry used is equivalent to conventional ECAP, but with a multi-channel die. Microstructure investigations demonstrating significant grain refinement confirm the viability of this approach.

火山岩貯留層のモデリングとフローシミュレーション：多点法地球統計学と確率摂動法の応用

A domestic gas field was modeled and flow-simulated. Its reservoir body comprises stacked rhyolite lava domes erupted under submarine environment. Porous network developed inside and chilling by seawater formed hyaloclastite to deposit around it. Although hyaloclastite is also porous, its permeability has been dramatically reduced by clay minerals. Impermeable basaltic sheets and mud seams are also present. Each facies plays a specific role in the pressure system of the field. Stratigraphic correlation originally identified multiple reservoirs. Gas has been produced according to priority assigned to each, assuming that it is sealed from others. However, it is noticed by now that pressures of unexploited units have also declined with variety of rates. In addition, some unusual local pressure behaviors have been recorded. It was decided to re-model the whole pressure system to reasonably explain these observations. Combination of multi-point geostatistics and probability perturbation theories was employed. It successfully reproduced non-linear features of stacked lava domes, while allowing pressure data for controlling geo-body distributions in larger scale. A common difficulty of building a proper training image, further pronounced for a volcanic reservoir, was solved by iteratively adjusting its prototype until the number of perturbations for history matching was minimized. Ambiguous reservoir boundary, due to lava growth in random directions, was stochastically represented by populating a predetermined modeling space with both pay and non-pay pixels. Resulted realizations closely simulate pressure history to every detail and look realistic in facies distribution. They ascribe the uneven pressure decline between different units to tortuous flow channels connecting them. They also uncovered the cause of the unusual smaller-scale pressure performances. OGIP evaluated by 20 equally probable realizations stay within ±15% around the mean. Incremental recovery by adding a new well indicates wider scatter than that by installing a booster compressor, which quantifies geological risk associated to it.

Sclerosing myoepithelial neoplasm: immunohistochemical and ultrastructural features in a unique case

Background Histopathologic features of myoepithelial tumors may vary and include spindled, plasmacytoid, epithelioid, and clear cells as well as mucoid to hyalinized matrix. Objective We present a unique myoepithelial neoplasm with dense sclerosis. Case report A19-year-old male presented with a 2-year history of a right buccal lesion. A poorly circumscribed submucosal lesion without ulceration or tenderness was located near Stenson's duct. Contributor's impression was “lipoma.” Pathologic features The specimen was 2.1 × 1 × 1 cm, very firm, and varied in color from tan-brown to yellow. Microscopic examination revealed very dense fibrous stroma that infiltrated striated muscle, adipose tissue, and minor salivary gland lobules. Small strands and irregular islands of cells with poorly defined plasma membranes, abundant pale eosinophilic fibrillar to vacuolated cytoplasm, and oval to round nuclei were embedded in, and often compressed by, the dense stroma. Ductal structures and chondroid matrix were not present. Tortuous thin-walled vascular channels were common. The cellular strands and nests reacted with antibodies for S-100, pancytokeratin (AE1/AE3) and GFAP, but not for SMA, CD34, or CD68. There was mild expression of CD99 and Bcl-2. Electron microscopy revealed occasional intermediate filament aggregates, hemidesmosomes, rare structures representing myofilament attachment plaques, basement membranes, and basal lamina material. Neural processes, neurosecretory granules, neurofilaments, and glial differentiation were not identified. Myoepithelial origin was supported by the histopathologic, immunohistochemical, and ultrastructural findings. Conclusion Dense sclerosis may be associated with myoepithelial neoplasms, and both immunohistochemical and ultrastructural examination may help define the cell of origin.

Shear induced anisotropy and heterogeneity of fluid flow in a single rock fracture with translational and rotary shear displacements ¿ a numerical study

The fluid flow and tracer transport in a single rock fracture during shear processes has been an important issue in rock mechanics and is investigated in this thesis using Finite Element Method (FEM) and streamline particle tracking method, considering evolutions of aperture and transmissivity with shear displacement histories under different normal stresses, based on laboratory tests. The distributions of fracture aperture and its evolution during shear were calculated from the initial aperture fields, based on the laser-scanned surface roughness features of replicas of rock fracture specimens, and shear dilations measured during the coupled shear-flow-tracer tests in laboratory performed using a newly developed testing apparatus in Nagasaki University, Nagasaki, Japan. Three rock fractures of granite with different roughness characteristics were used as parent samples from which nine plaster replicas were made and coupled shear-flow tests was performed under three normal loading conditions (two levels of constant normal loading (CNL) and one constant normal stiffness (CNS) conditions). In order to visualize the tracer transport, transparent acrylic upper parts and plaster lower parts of the fracture specimens were manufactured from an artificially created tensile fracture of sandstone and the coupled shear-flow tests with fluid visualization was performed using a dye tracer injected from upstream and a CCD camera to record the dye movement. A special algorithm for treating the contact areas as zero-aperture elements was used to produce more accurate flow field simulations by using FEM, which is important for continued simulations of particle transport, but was often not properly treated in literature. The simulation results agreed well with the flow rate data obtained from the laboratory tests, showing that complex histories of fracture aperture and tortuous flow channels with changing normal stresses and increasing shear displacements, which were also captured by the coupled shear-flow tests of fracture specimens with visualization of the fluid flow. From the obtained flow velocity fields, the particle transport was predicted by the streamline particle tracking method with calculated flow velocity fields (vectors) from the flow simulations, obtaining results such as flow velocity profiles, total flow rates, particle travel time, breakthrough curves and the Peclet number, Pe, respectively. The fluid flow in the vertical 2-D cross-sections of a rock fracture was also simulated by solving both Navier-Stokes (NS) and Reynolds equations, and the particle transport was predicted by streamline particle tracking method. The results obtained using NS and Reynolds equations were compared to illustrate the degree of the validity of the Reynolds equation for general applications in practice since the later is mush more computationally efficient for large scale problems. The flow simulation results show that the total flow rate and the flow velocity predicted by NS equations are quite different from that as predicted by the Reynolds equation. The results show that a roughly 5-10 % overestimation on the flow rate is produced when the Reynolds equation is used, and the ideal parabolic velocity profiles defined by the local cubic law, when Reynolds equation is used, is no longer valid, especially when the roughness feature of the fracture surfaces changes with shear. These deviations of flow rate and flow velocity profiles across the fracture aperture have a significant impact on the particle transport behavior and the associated properties, such as the travel time and Peclet number. The deviations increase with increasing flow velocity and become more significant when fracture aperture geometry changes with shear. The scientific findings from these studies provided new insights to the physical behavior of fluid flow and mass transport in rock fractures which is the scientific basis for many rock mechanics problems at the fundamental level, and with special importance to rock engineering problems such as geothermal energy extraction (where flow rate in fractures dominates the productivity of a geothermal energy reservoir) and nuclear waste repositories (where radioactive nuclides transport through fractures dominates the final safety evaluations) in fractured rocks.

Flow of magnetorheological fluid through porous media

Flow of a magneto-rheological (MR) fluid through different types of porous media (bundle of cylinders, packed beds of magnetic and non-magnetic spheres and cylinders) is considered, both theoretically and experimentally. The theory is based on averaging the magnetic and rheological properties of MR fluid in tortuous channels making different angles between local field and local velocity. A comparison of the pressure drop through porous beds and spiral channels is analyzed and practical recommendations are developed. It is shown that the mean yield stress of Bingham MR fluid (as well as the pressure drop, Δ P) depends on the mutual orientation of the external magnetic field and the main axis of the flow. This theory is tested against our experimental results and is shown to well predict the pressure drop obtained in different porous media.

EIS analysis of hydroperoxide ion generation in an uncatalyzed oxygen-diffusion cathode

Oxygen reduction to hydroperoxide ion in a 0.5 mm-thick porous uncatalyzed carbon-polytetrafluoroethylene electrode has been studied by electrochemical impedance spectroscopy using different experimental conditions such as KOH concentrations from 1.0 to 6.0 M, constant applied potentials with steady cathodic current densities in the range 5–100 mA cm −2, O 2 partial pressures of 0.21–1.0 atm and temperatures from 5.0 to 55.0 °C. The Nyquist diagrams show a main semicircle, assigned to dominating charge transfer and weak adsorption, together with a low-frequency semicircle, assigned to diffusion. The parameters of the equivalent circuit have been related to structural aspects of the electrode. The fitting results indicate increasing an electroactive area towards the electrolyte side when the overpotential increases. The low-frequency behaviour, interpreted using the finite-length diffusion model, is ascribed to the diffusion of electrogenerated hydroperoxide ion through the electrode pores. The gas diffusion cathode apparently has higher electroactive area approaching the electrolyte side and also, some tortuous electrolyte channels penetrating some tens of microns into its porous structure. The increase in its double layer capacity with increasing KOH concentration, cathodic current density and temperature, is explained by a higher electroactive area due to an increase in the electrode wetting.

The Influence of Node-Fibril Morphology on Healing of High-Porosity Expanded Polytetrafluoroethylene Grafts

Purpose: To manufacture high-porosity expanded polytetrafluoroethylene (ePTFE) vascular grafts with the same internodal distance but different node-fibril morphology, and to evaluate their biologic behaviors in a canine carotid artery implantation model. Materials and Methods: Several types of high-porosity ePTFE vascular grafts with the same inside diameter (4 mm) and wall thickness (650 µm) were manufactured under different heating, stretching conditions. The luminal surface and cross section of the grafts were photographed by scanning electron microscopy and the node-fibril structure was examined. Two typical types of high-porosity ePTFE vascular grafts were then selected and proceeded to an animal study. The test grafts were explanted after an interval of 12 weeks and subjected to histomorphometric analyses. Results: The following two types of high-porosity ePTFE vascular grafts were selected; one had a through-pore structure extending from the outer to the inner surface and the other had a random-node architecture with tortuous path channels extending from the outer to the inner surface. The histomorphometric analyses of thrombus-free surface, thickness of pseudointima, cellular ingrowth, capillary ingrowth, and cellular proliferation revealed no significant differences between the grafts. Conclusion: In high-porosity ePTFE vascular grafts, graft healing enhanced by transmural tissue ingrowth may be not largely dependent on node-fibril morphology. This knowledge will be helpful to design a new type of high-porosity ePTFE vascular grafts available for clinical use.

Branch Retinal Vein Occlusion in a Japanese Patient with Neurofibromatosis 1

Background: To report an Asian patient with branch retinal vein occlusion secondary to neurofibromatosis 1. Case: A 64-year-old woman presented with a loss of vision in her right eye of 9-month duration. A diagnosis of neurofibromatosis 1 was made. A general medical examination showed no abnormalities except the signs of neurofibromatosis 1. Observations: Fundus examination of the right eye revealed irregularities of the venous caliber, partial sheathing of the corresponding vein and macular edema. Multiple dilated and tortuous collateral channels and an arteriovenous communication bridged the perfused and nonperfused retina. Fundus examination of the left eye showed a tortuous vein in the temporal region of the fovea. Fluorescein angiography of the right eye confirmed delayed filling in a superotemporal artery and in the corresponding vein. The temporal region of the fovea had large areas of capillary loss. The collaterals were tortuous and mimicked a neovascularization. Fluorescein angiography of the left eye confirmed that the vein in the temporal part of the fovea was tortuous and not leaking. A diagnosis of branch retinal vein occlusion of the superotemporal vein was made. Conclusions: Neurofibromatosis 1 should be considered in the differential diagnosis of retinal vascular occlusive disease without other risk factors.

Molecular genetics of vascular malformations.

Vascular malformations are localized errors of angiogenic development. Most are cutaneous and are called vascular 'birthmarks'. These anomalies are usually obvious in the newborn, grow commensurately with the child, and gradually expand in adulthood (Mulliken and Glowacki, 1982). Vascular malformations also occur in visceral organs, such as the respiratory and gastrointestinal tract, but are more common in the brain (Mulliken and Young, 1988). These anomalies are composed of tortuous vascular channels of varying size and shape, lined by a continuous endothelium and surrounded by abnormal complement of mural cells. Vascular malformation can be life threatening due to obstruction, bleeding or congestive heart failure. Most anomalies occur sporadically, but there are families exhibiting autosomal dominant inheritance. Genetic studies of such families have resulted in the identification of mutated genes, directly giving proof of their important role in the regulation of angiogenesis.

Facial “glomangiomas”: Large facial venous malformations with glomus cells

Background: “Glomangiomas” are benign cutaneous vascular lesions consisting of convoluted, abnormally formed venous channels lined by cuboidal and oval epithelioid, α-actin-positive, glomus cells. Three different clinical variants of glomangioma have been recognized: solitary, multiple, and nodular, or plaquelike. Inheritable forms are common. Objective: We describe in 7 patients (2 of them having a familial glomangiomatosis) the rare facial location of glomangiomas to differentiate this type from common facial venous malformation (VM). Methods: We analyzed clinical data (photographs), course, investigations (computed tomographic scans in 4 patients, magnetic resonance imaging in 6, arteriography in 2, direct puncture phlebography in 4, and pathologic examinations in all 7), and outcome with treatment. Results: Lesions were soft, composed of multiple nodules, confluent and plaquelike, deep blue or blue-to-purple, sometimes sagging, one-sided in a cheek, extending to the lips in 5 patients, to the chin in 4, and to the lower eyelid in 4. They were poorly compressible, a finding different from common facial VMs. In a young man extensive back involvement was associated. Among radiologic investigations, only magnetic resonance imaging after gadolinium enhancement offered some differential features with common VMs. However, histopathologic examination clarified the differential diagnosis: although the large tortuous venous channels were reminiscent of capillary-venous malformation, in many vessels the walls contained one or several rows of glomus cells. Conclusion: Multiple plaquelike facial “glomangiomas” mimic a common venous malformation because of their blue hue. However, with experience, one can clinically recognize them, and their pathologic aspect is distinctive. Management should differ slightly from that for common facial VM because sclerotherapy has proven to be less effective. Therefore surgical treatment is the only helpful therapeutic option. (J Am Acad Dermatol 2001;45:239-45.)