Vein-like Structures Research Articles

Gestational Modification of Murine Spiral Arteries Does Not Reduce Their Drug-Induced Vasoconstrictive Responses In Vivo1

Dynamic control of maternal blood flow to the placenta is critical for healthy pregnancy. In many tissues, microvasculature arteries control the flow. The uterine/endometrial vascular bed changes during pregnancy include physiological remodeling of spiral arteries from constricted artery-like structures to dilated vein-like structures between Gestation Day 8 (gd8) and gd12 in mice and wk 12-16 in humans. These changes occur, in part, due to local environmental changes such as decidualization, recruitment of maternal uterine natural killer cells, and invasion of conceptus-derived trophoblasts. No current preparations permit in vivo testing of decidual microvascular reactivity. We report an in vivo intravital fluorescence microscopy model that permits functional study of the entire uterine microvascular bed (uterine, arcuate, radial, basal, and spiral arteries) in gravid C57BL/6 mice. Vascular reactivities were measured at gd8 prespiral arterial remodeling and gd12 (postremodeling) to a range of concentrations of adenosine (10(-8)-10(-6) M), acetylcholine (10(-7)-10(-5) M), phenylephrine (10(-7)-10(-5) M), and angiotensin II (10(-8)-10(-6) M). At baseline, each arterial branch order was significantly more dilated on gd12 than gd8. Each microvascular level responded to each agonist on gd8 and gd12. At gd12, vasodilation to adenosine was attenuated in uterine, arcuate, and basal arteries, while constrictor activity to angiotensin II was enhanced in uterine and arcuate arteries. The tendency for increasing vasoconstriction between gd8 to gd12 and the constrictor responses of modified spiral arteries were unexpected findings that may reflect influences of the intact in vivo environment rather than inherent properties of the vessels and may be relevant to ongoing human pregnancies.

Finger vein segmentation in infrared images using supervised and unsupervised clustering algorithms

In this paper, two new methods to segment infrared images of finger in order to perform the finger vein pattern extraction task are presented. In the first, the widespread known and used K nearest neighbor (KNN) classifier, which is a very effective supervised method for clustering data sets, is used. In the second, a novel clustering algorithm named nearest neighbor clustering algorithm (NNCA), which is unsupervised and has been recently proposed for retinal vessel segmentation, is used. As feature vectors for the classification process in both cases two features are used: the multidirectional response of a matched filter and the minimum eigenvalue of the Hessian matrix. The response of the multidirectional filter is essential for robust classification because offers a distinction between vein-like and edge-like structures while Hessian based approaches cannot offer this. The two algorithms, as the experimental results show, perform well with the NNCA has the advantage that is unsupervised and thus can be used for full automatic finger vein pattern extraction. It is also worth to note that the proposed vector, composed only of two features, is the simplest feature set which has proposed in the literature until now and results in a performance comparable with others that use a vector with much larger size (31 features). NNCA evaluated also quantitatively on a database which contains artificial images of finger and achieved the segmentation rates: 0.88 sensitivity, 0.80 specificity and 0.82 accuracy.

Longitudinal fundus and retinal studies with SD-OCT: a comparison of five mouse inbred strains

Spectral domain optical coherence tomography (SD-OCT) has recently been established as a method for in vivo imaging of fundus and retina in the mouse. It enables more effective studies of retinal diseases including investigations of etiopathologic mechanisms. In order to learn more about longitudinal fundus development and to enable recognition of disease-associated irregularities, we performed confocal scanning laser ophthalmoscopy (cSLO) and SD-OCT measurements in the inbred strains C57BL/6J, C3HeB/FeJ, FVB/NCrl, BALB/cByJ, and 129S2/SvJ when they were between 2 and 6months of age. In general, cSLO and SD-OCT data did not reveal sex-specific or unilateral differences. C3HeB/FeJ and FVB/NCrl mice showed diffuse choroidal dysplasia. Choroidal vein-like structures appeared as dark fundus stripes in C3HeB/FeJ. In FVB/NCrl, fundus fleck accumulation was found. In contrast, only minor time-dependent changes of fundus appearance were observed in C57BL/6J, BALB/cByJ, and 129S2/SvJ. This was also found for individual fundic main blood vessel patterns in all inbred strains. Vessel numbers varied between 6 and 13 in C57BL/6J. This was comparable in most cases. We further found that retinae were significantly thicker in C57BL/6J compared to the other strains. Total retinal thickness generally did not change between 2 and 6months of age. As a conclusion, our results indicate lifelong pathologic processes in C3HeB/FeJ and FVB/NCrl that affect choroid and orbital tissues. Inbred strains with regular retinal development did not reveal major time-dependent variations of fundus appearance, blood vessel pattern, or retinal thickness. Consequently, progressive changes of these parameters are suitable indicators for pathologic outliers.

Histological approach to Bacillus subtilis colony-biofilm: evolving internal architecture and sporulation dynamics.

Bacillus subtilis has been used as a classic model to study biofilm formation and sporulation process. Colonies of wild-type strains usually have a complex external morphology, but the details of their internal architecture are still undisclosed. Since bacterial biofilms fulfill the criteria to be considered tissues, the aim of this work was to analyse B. subtilis colony-biofilm internal architecture evolution and sporulation dynamics using histological techniques. Transversal sections of colony-biofilms incubated from 24 hours up to 20 days were stained using histochemical techniques to analyse the internal structure by light and electron microscopy. A morphometric study of the different structural biofilm components was performed by image analysis, and an application to quantify spores was developed. Internal biofilm architecture was characterised by a stratified pattern, which evolved from 3 strata at 24 hours, up to 5 strata at 20 days. At 48 hours, strata at the central area of the biofilm was folded, resulting in elevated structures (vein-like structures) that could reach up to 465 μm in height. Sporulation started at 48 hours, at the top of the vein-like structures, at the interface between the two uppermost strata. At 20 days spores formed a continuous central layer, representing 7.5% of the total biofilm. In summary, our results demonstrate that B. subtilis colony-biofilm has a complex and organized internal architecture, evolving over time, and taking place in different cell subpopulations with different functionalities. Furthermore, in situ spore quantification described in this work could be a good alternative to the classical chamber counting.

Metal veins in the Kernouvé (H6 S1) chondrite: Evidence for pre- or syn-metamorphic shear deformation

Kernouvé is an H6 chondrite that experienced a very small degree of late stage shock loading (S1). However, Kernouvé contains Fe–Ni metal vein-like structures, whose formation have been attributed to an early impact event. To establish the formation conditions of metal veins in Kernouvé, we examined the three dimensional (3D) arrangement of metal vein-like structures and typical metal grains in two samples of Kernouvé with X-ray microtomography (μCT) at resolutions of ∼11μm/voxel. We additionally investigated the 3D structure of the porosity present in Kernouvé using μCT at two different resolutions (∼3 and ∼11μm/voxel). These data and optical microscopy support the hypothesis that Kernouvé has experienced little post-metamorphic shock. However, the moderate 5.8vol.% porosity of Kernouvé is in the form of intergranular voids rather than cracks, which indicates any cracking that may have existed in the relatively brittle silicate grains was annealed. We estimate that 70–80% of the primordial porosity in Kernouvé was removed by impact-related compaction. Moreover, we found no collective orientation of metal grains, so high metamorphic temperatures following compaction erased any common orientation of metal grains due to compaction. We propose that the metal vein structures can be explained as a pre- or syn-metamorphic shock-induced process, which we infer was primarily shear deformation, with some uniaxial compaction also occurring. The coarse metal veins probably formed by accumulation of ductile metal grains along shear zones, a process that would have been facilitated by having an already warm H chondrite parent body when shock occurred (i.e., syn-metamorphic shock). The complexity of shape, including numerous tendrils expanding from the primary structure, of the veins in Kernouvé is likely due to the coalescence of metal by metamorphic growth after the shear event. The metal veins in Kernouvé thus appear to record evidence for early, shock-induced metal mobilization and the maximum shock pressure experienced by Kernouvé may have been ⩽21GPa. Our study suggests that collision-induced segregation of metal occurred at an early stage in low-gravity planetesimals, consistent with the idea that this process could have been important for the differentiation of such objects.

Rathke’s pouch remnant and its regression process in the prenatal period

During ontogeny, part of Rathke's pouch, a physiologically superior pouching of the stomodeal ectoderm, may remain, forming the usual anomaly known as Rathke's cleft cyst. More rarely, however, the entire pouch (i.e., the craniopharyngeal canal) remains, resulting in transsphenoidal meningoencephalocele. This study is aimed to provide a better understanding of the pathogenesis. We histologically evaluated the inferior protrusion of the putative hypophysial fossa in 35 embryonic and fetal heads, respectively (15 at 5-8weeks and 20 at 12-16weeks of gestation). In 3 of the 35 specimens, we observed a complete cleft originating from the adenohypophysis, passing through the sphenoid and connecting with the pharyngeal epithelium or pharyngobasilar fascia. In another 18 specimens, we observed a duct-like structure protruding from the fossa and ending in the sphenoid. The sellar protrusion contained vein-like structures and debris of red blood cells. The protrusion was located on the anterior or anterosuperior side of the notochord. No ossification center was observed around the sellar region of the embryos. Although ossification occurred in 12 of the 20 fetuses, nine of the latter showed no evidence of cleft or protrusion, indicating that the incidence of Rathke's pouch remnant was lower in the fetuses (11/20) than in the embryos (11/15). Rathke's pouch may be closed by ossification of the sphenoid, but increased cell proliferation and/or large amounts of degenerated veins may provide a structure resistant to the mechanical pressure caused by ossification.

Dynamic Tensile Property of Zr-based Metallic Glass/Porous W Phase Composite

The dynamic tensile deformation and fracture behavior of the Zr-based metallic glass/porous W phase composite were investigated at room temperature by means of the Split Hopkinson Tension Bar (SHTB). It was found that the composite exhibited no appreciable macroscopic plastic deformation prior to catastrophic fracture and the fracture surface was perpendicular to the axial direction. Substantive micro cracks were observed along the interface between W grains or the interface between the metallic glass phase and the W phase. Scanning electron microscopy (SEM) observations revealed that vein-like patterns, dimple-like patterns and substantive ridge-like structures were the typical fracture morphologies on the fracture surface for the metallic glass phase and the morphology of the W phase is a mixture of intergranular and transgranular fracture. Based on those results referred above, the dynamic tensile deformation and fracture mechanism of the Zr-based metallic glass/porous W phase composite were discussed in detail.

Intrusive origin for Upper Group (UG1, UG2) stratiform chromitite seams in the Dwars River area, Bushveld Complex, South Africa

Detailed geological mapping, core logging and petrographic analysis are supplemented with geochemical data to evaluate the petrogenesis of the Upper Group (UG1, UG2) stratiform chromitite seams in the Dwars River area, Bushveld Complex. Seven important and widespread features of UG1 and UG2 chromitite are addressed: (1) chromitite seams are dissociated from specific silicate successions and enclosed in Cr-rich silicates with a common genetic origin, (2) chromitite seams cut structures and textures in host silicates, have vein-like structures and host xenoliths, (3) chromitite seams are braided, (4) chromite grain distributions suggest flow segregation, (5) silicates in chromitite seams have modal proportions, forms and compositions different from those in binding silicate rocks, (6) PGE distributions in UG2 chromitite suggest flow segregation, and (7) chromitite seams are bound by coarse-grained silicates possibly formed through contact heating and/or de-volatization. These features are integrated into a model whereby UG chromitite seams developed from the intrusion of chromite crystal slurries. This model proposes that chromite grains first accumulated within structural traps of the Bushveld conduits, and that these accumulations were then re-mobilized with silicate melt (± sulfides and/or fluids?) to spread laterally as chromite crystal slurries within the layered ultramafic-mafic cumulates of the Bushveld Complex.

Thyroid hormone deficiency changes the distribution of oligodendrocyte/myelin markers during oligodendroglial differentiation in vitro

Myelination depends on the proper differentiation of oligodendrocytes and several factors may influence this event. For instance, thyroid hormone (T3) affects the timing of differentiation and regulates the expression of several enzymes involved in the synthesis of complex lipids and in the expression of some myelin structural proteins. We investigated the effect of T3 deficiency on oligodendroglial differentiation and in the distribution of oligodendrocyte/myelin proteins 2′3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) and myelin basic protein (MBP). Oligodendroglial-enriched cultures were obtained from cerebra of neonate rats grown in a modified medium. The T3-deficient status was induced by using medium devoid of T3. We observed a delay, in T3-deficient cultures, in oligodendroglial maturation characterized by less extensive processes and membrane vellum than in controls. In control cultures, CNPase immunoreactivity was punctated, showing cell bodies and processes at earlier stages and redistribution to cytoskeleton vein-like structures in later stages. In T3-deficient cultures, CNPase remained in a punctated pattern and only at 10 days in vitro we observed CNPase redistribution to the presumptive cytoskeleton vein-like structures. MBP in control cultures was distributed through the whole cell body and processes whereas in T3-deficient cultures, MBP immunoreactivity was concentrated in the perinuclear region. These results reinforce the hypothesis that T3 is an important factor in oligodendrocyte differentiation, particularly regarding the distribution of myelin proteins.

The Openings of Uteroplacental Vessels With Villous Infiltration at Different Gestational Ages

The number of uteroplacental vessels flowing into the intervillous space in mature placentas has been reported in some studies to increase and in others to decrease. Both villous infiltration and proliferation in the vessels have been neglected in histologic examinations and need to be studied. To clarify these conflicting findings regarding villous infiltration and proliferation in the uteroplacental vessels. A retrospective study was done using placental sections of different gestational ages. The openings of the vessels in each section were counted, noting if they were with or without villous infiltration. The frequency of openings per section was calculated, and the findings were grouped by gestational age. The frequency of total openings was significantly lower in the 41 to 37 weeks group (1.2) than in the 36 to 30 weeks group (2.0), the 29 to 20 weeks group (2.2), and the 19 to 13 weeks group (2.4) (P < .001). The frequency of openings with villous infiltration decreased similarly in mature placentas. Chorionic villi infiltrated the openings and proliferated in uteroplacental vessels. Differentiation between arteries and veins was difficult in the basal plate, because all vessels had veinlike structures. This decreasing frequency of openings in mature placentas suggests that the amount of intervillous blood flow is limited in full-term and postterm pregnancy. Villous infiltration into the vessels is considered a normal finding with gestation and can provide trophoblast for uteroplacental arteries. The relationship between placental development and villous proliferation in the vessels is presented.

Tensile fracture characteristics and deformation behavior of a Zr-based bulk metallic glass at high temperatures

The fracture characteristics of the Zr 41.25Ti 13.75Ni 10Cu 12.5Be 22.5 (at.%) bulk metallic glass subjected to tensile tests at room temperature, the calorimetric glass transition temperature, and in the supercooled liquid region have been studied. The fracture behavior at high temperatures under tension deformation can be classified as three modes, i.e. brittle fracture, necking fracture and sustainable deformation, which strongly depend on the test temperature and strain rates. Typical vein-like structures are dominant on the brittle fracture surfaces at high temperatures while cleavage veins with round-cores are observed at room temperature. The high-temperature deformation behavior and the underlying controlling mechanisms are discussed in the frame of the ‘free volume’ theory.

Raman investigation of stress and phase transformation induced in silicon by indentation at high temperatures

To study the material deterioration at and around the support contacts during processing of silicon waters, we used Rock-well indentation at elevated temperatures as a model. Cz-silicon was subjected for 30 s to a load of 1.5 N, at temperatures between 70 °C and 660 °C. The resulting morphology was checked by Scanning Electron Microscopy. Micro Raman Spectroscopy was used to monitor residual stress and tilt, occurrence of silicon polymorphs. We found strong compressive stress inside the indented area, with a dramatic drop and reversal to tensile stress at its boundary. The morphology shows a top hat profile, covered with a mesh of vein-like structures. Crystalline phases such as Si-III, Si-IV, Si-XII, and amorphous silicon are observed. Outside the spot, the situation depends strongly on the indentation temperature. Up to 400 °C the material appears practically unstressed, with a high density of relaxation cracks. At 500 °C and 600 °C a transition is found from strong tensile stress at the boundary to another region of compressive stress extending over more than 40 μm, associated with a significantly lower crack density. At still higher temperature (660 °C) the crack density tends to zero. and comparably weak stress seams to oscillate between compressive and tensile.

Cristobalite inclusions in the Tatahouine achondrite: Implications for shock conditions

The mineralogy of the Tatahouine diogenite was investigated by optical microscopy, Raman micro-spectrometry, and scanning and transmission electron microscopies. Inclusions of α-cristobalite in orthopyroxenes, locally in symplectic association with chromites, or associated with metal, have been characterized for the first time in a diogenite. Mosaicism of the orthopyroxenes indicates shock effects in the meteorite. The shock history of the meteorite must be consistent with the presence of vein-like structures containing inclusions of well-crystallized cristobalite, a low-pressure, high-temperature phase. Several possible mechanisms to account for these observations are discussed. The simplest one, consistent with all observations, is that a shock event would have occurred in a hot orthopyroxenite, either before extensive cooling of the asteroid, or in materials heated by previous impacts and maintained hot under an ejecta blanket.

Redistribution of cholesterol in oligodendrocyte membrane sheets after activation of distinct signal transduction pathways

Cultured oligodendrocytes produce extensive membrane sheets that contain an internal lacy network of vein-like structures composed of microtubules, actin filaments, and 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNPase). These cytoplasmic vein-like structures surround domains of myelin basic protein (MBP). Using the antibiotic filipin, that binds to cholesterol, the relationship between plasma membrane cholesterol and cytoskeleton in membrane sheets was examined. Our results show that cholesterol was relatively uniformly distributed within the plasma membranes of prefixed control oligodendrocyte membrane sheets. When live cultures were extracted with Triton X-100, however, a subpopulation of cholesterol molecules remained colocalized with cytoskeleton in the membrane sheets. Activation of two well-characterized signaling pathways that differentially affect microtubule and actin filament stability in membrane sheets resulted in an apparent massive lateral movement of cholesterol molecules away from membrane regions overlying internal MBP domains to membrane tracts directly overlying cytoplasmic cytoskeletal veins. Depolymerization of microtubules by colchicine resulted in redistribution of cholesterol directly over actin filaments, whereas depolymerization of actin filaments by cytochalasin B resulted in redistribution of cholesterol directly over CNPase/microtubular veins. These data suggest that cholesterol forms an association with cytoskeletal components or proteins associated with cytoskeleton. These data also suggest that cholesterol, via interactions with cytoskeleton, plays a role in signaling pathways in oligodendrocyte membrane sheets.

Regulation of cytoskeleton by myelin components: studies on shiverer oligodendrocytes carrying an Mbp transgene.

Oligodendrocytes from the shiverer mutant mouse are missing most of the myelin basic protein (Mbp) gene. In axon-free cultures, they produce membrane sheets with abnormally assembled microtubule and actin-based structures. This suggests that an Mbp gene product may have an important role in regulating the organization and stability of the wild-type oligodendrocyte cytoskeleton. We now present evidence extending these observations, using cultured oligodendrocytes that carry both the shiverer mutation and the Mbp1 transgene which partially corrects their deficit. Shiverer oligodendrocytes that carry one dose of the Mbp1 transgene abnormally express MBP along major cytoskeletal vein-like structures in processes and sheets. Shiverer oligodendrocytes that carry two doses of the Mbp1 transgene contain two types of membrane sheet regions, i.e. regions filled with aberrant punctate foci of MBP, and regions with normal domains of MBP. Immunocytochemical staining data show that the distribution of cytoskeleton and associated 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) is dependent upon how MBP is organized. Bundling of actin filaments occurs only around MBP domains, and the colocalization of CNPase along microtubular structures also appears to be regulated by MBP domains in sheets. Multinucleated oligodendrocytes are observed, a likely result of the inability of dividing pro-oligodendrocytes to bundle actin filaments. In addition, the ability of MBP to mediate extracellular signals that modulate cytoskeleton appears to be dependent upon MBP's organization. Transduction of the galactocerebroside signaling pathway, which results in the destabilization of microtubules but not actin filaments, occurs only in sheets containing MBP domains. The distribution of MBP, however, does not affect the myelin/oligodendrocyte-specific protein signaling pathway, which results in growth of microtubular structures and extensive destabilization of the actin cytoskeleton.

Reductilization of embrittled LaAlNi amorphous alloys by viscous flow deformation in a supercooled liquid region

A viscous flow deformation at high strain rates exceeding a critical value in the supercooled liquid region was found to induce the ductilization of an amorphous La 55Al 25Ni 20 alloy which was embrittled by annealing at temperatures below T g. The appearance of the tensile fracture surface also changed from a shell-like pattern typical for the brittle amorphous alloy to a pattern consisting of smooth regions and regions with vein-like structures typical for the ductile amorphous alloy. The embrittled samples exhibit an endothermic reaction resulting from the annihilation of the short-range ordering developed during annealing, accompanying the disappearance of an exothermic reaction. The deformed samples with good ductility do not show the endothermic reaction but exhibit only the exothermic reaction. Accordingly, the deformation-induced reductilization is presumed to result from the introduction of excess free volume and the formation of deformation-induced disordered atomic configuration.

Redistribution and internalization of antibodies to galactocerebroside by oligodendroglia

Glial cultures from mouse brain were used to examine the direct interaction between oligodendroglia and antibodies to galactocerebroside (GalC). The external surface of oligodendroglial membrane sheets showed large GalC+ patches separated by a GalC- network after exposure to anti-GalC and fluoresceinated second antibody at 37 degrees C. However, the membrane sheets were evenly stained when cultures were fixed prior to staining or stained at 0 degrees C. Further, exposure to second antibody at 0 degrees C or to Fab fragments of second antibody at 37 degrees C also gave even staining. These results indicate that GalC is normally distributed evenly on the surface of oligodendroglial membrane sheets, but that redistribution or patching of GalC:anti-GalC complexes occurs by cross-linking with second antibody at 37 degrees C. Antibodies to GalC are internalized rapidly and specifically by oligodendroglia. This process is temperature-dependent, and, in contrast to patching, does not require the presence of second antibody. Internalized antibodies are seen within 1 min throughout oligodendroglial membrane sheets, then aggregate in the sheets and in large vein-like structures leading to the cell body. By 1 hr, the cell body is densely packed with vesicles containing anti-GalC. By 24 hr after a 10 min exposure to anti-GalC, internal antibody has disappeared. Anti-GalC is recycled to the cell surface within 5 min after exposure, and continues to appear on the surface for at least 4 hr after the pulse.

Origin of Precambrian iron-formations in the Lake Superior region

The Precambrian banded, cherty iron-formations in the Lake Superior region were deposited on broad continental shelves, and deposits of the supratidal, intertidal, and subtidal zones can be recognized in the well-known facies of the iron-formations. The supratidal deposits were primarily calcitic, aragonitic, and sideritic muds. Other minerals, in order of decreasing abundance, may have been gypsum, anhydrite, ankerite, dolomite, quartz, apatite, and halite. Intraclasts were produced by desiccation-granulation, and some of this material was redeposited in the intertidal and subtidal zones. The intertidal zone was characterized by the development of extensive algal reefs and digital-sized and larger stromatolitic mounds. Desiccation-granulation and tidal rip of mineralized stromatolites further added to the accumulation of intraclasts. The intertidal zone was the domain of granules that were derived by abrasion and rounding of intraclasts. The original mineralogy of the intertidal deposits was similar to that of the supratidal zone; however, because of photosynthesis, the sea water was oxygenated. Lozenge-shaped grains are considered to be secondary, silicified, and iron-oxide replicates of original gypsum crystals, and, by comparison with recent evaporites, some anhydrite and halite may also have been present. The deposits of the intertidal and subtidal zones are considered to be comparable to the present-day Abu Dhabi complex in the Persian Gulf. Spherical microstructures are abundant and well preserved in the chert of the subtidal deposits. Pyrite, which characterizes these deposits, probably was formed largely by the bacterial reduction of sulfate derived from the intertidal zone. The laminations in the iron-formations resulted from several causes that were controlled by chemical and mechanical processes, such as the rates and localization of the precipitation of calcitic, aragonitic, and sideritic muds and the mechanical breakup and redistribution of these sediments as sand, silt, and mud. These processes resulted in compositional and textural laminations. The diversity of the banded, cherty iron-formations, recognized in the different facies, then, can be explained largely in the diagenetic changes. The large-scale pervasive diagenetic changes were the replacement of calcite and aragonite by chert and the formation of iron silicates by the reactions between ionic silica and siderite and iron-bearing dolomite. Vein-like structures and the development of magnetite along stylolites indicate mobility of iron in late diagenetic stages, and iron-organic chelates are suggested to account for the mobility. Depending on the composition of the laminae and the chemical environment, silicification during diagenesis produced the hematite, magnetite, siderite, pyrite, and mixed-mineral facies.

Crystal growth in cataclasites: Diagnostic microstructures and implications

Abstract Microstructures in cataclasites from low- and high-angle fault zones in granitic basement rocks of the Scandinavian Caledonides indicate the operation of several processes. Intensive formation of microcracks filled with fine-grained mineral fragments indicates brittle deformation. The formation of quartz crystals with euhedral terminations suggests crystal growth. Occurrence of undulose extinction, deformation lamellae and grain boundary recrystallization in other quartz grains illustrates plastic deformation. Crystal growth causes (micro)cracks to heal and thereby changes the behaviour of rocks undergoing brittle deformation. The crystallization products vary in size from c 10 μm to c. 5 mm. Narrow banding parallel to rhomb and prism planes is indicative of crystal growth. The growth bands show slightly different crystallographic misorientation. In some cases the boundaries of these bands could be identified as dislocation arrays decorated by bubbles. The occurrence of fibrous chalcedony aggregates and transitions from extremely fine-grained quartz to large grains with euhedral terminations suggests the presence of colloidal silica-bearing fluids during growth. The crystallization process leads to the formation of vein-like structures. After crystallization plastic deformation may take place, followed by brittle deformation and new crystal growth. It is concluded that during the formation of the cataclasites a cyclic operation of brittle failure, crystal growth followed by plastic deformation took place, and this cycle was repeated several times.

Description de formations quaternaires semblables a des 'diapirs' dans les alluvions anciennes de la Seine et de la Marne pres de Paris

Abstract Several quarries southwest of Paris, near the confluence of the Marne with the Seine, display uplifts of the Ludian Eocene marls. Despite their small size, they are termed diapirs in that they tilt and pierce the overlying strata. The Bonneuil quarry shows six diapirs, varying in shape and orientation. They all display steep slopes, convex summits, and severe tilting of overlying Quaternary gravel beds. Some are isolated and others form complexes representing high points of single uplifts. The Trioux a Chelles quarry has 12 diapirs, several cut in vertical section. In addition to being pierced by marl diapirs, the overlying Quaternary gravel beds of both quarries are injected with thin marly veinlike structures. The complex form of the diapirs, interpenetration of the injections and accommodation of overlying strata to uplift suggest that the deformations were produced when the marls were in a softened state.