Further studies on structure of the organic components in mother-of-pearl, especiallly in pelecypods (Part 1)

1. The thin fragments of leaflets resulting from ultrasonic irradiation of the organic membranes of conchiolin freed by decalcification of mother-of-pearl by chelating agents, have been studied with the electron microscope in six species of Gastropods and in 30 species of Pelecypods. The material includes shells found in archaeological excavations and subfossil species. 2. In all the specimens, the fragments appear in the shape of lacelike reticulated sheets, perforated by openings or pores separated by cylindrical or strand-like trabeculae. 3. The average diameter, the frequency, and the relative surface of the pores in the reticulated sheets, have been measured. Previous conclusions about statistically significant differences in the patterns at the class level between Gastropods and Pelecypods have been supported by the present observations. In Pelecypods, the present results have brought evidence of significant differences between the patterns at a subclass ( family ) level. 4. The successive steps of disruption of the reticulated sheets and of their trabeculae by protracted ultrasonic irradiation have been observed in several species (including Trigonia lamarckii, Grandidieria burtoni and Aetheria elliptica) . 5. The findings suggest that the trabeculae consist of a core of fibrils, coated in normal conditions by sheets or muffs of another material which appears in part in the shape of hemispherical protuberances of various sizes. The similarity of these mechanical effects of ultrasonic irradiation with modifications induced in previous studies in the organic reticulated sheets of mother-of-pearl by biochemical fractionation is discussed. It is assumed that differences in the size and in the arrangement of the fibrils forming the core of the trabeculae, and that variations in the spatial relations between fibrils and coating substances might account for the taxonomical differences recorded between species with regard to the pattern of the organic lace-like reticulated sheets

Fixatives, Decalcifiers and Ultrastructure of the organic remnants from mural Nacreous Layers of Fossil Cephalopod Shells

The ultrastructure of the organic remnants has been compared in the TEM, after decalcification of the mural nacre of ammonites and fossil nautiloids by EDTA, which removes a soluble fraction, and after fixation and decalcification by formaldehyde-cetyl-pyridinium chloride-EDTA (CPC method) and chromium sulphate solutions, which are both considered to insure a better preservation of these organic remains. The loose networks of altered trabeculae, frequently fused into membranes, which constitute the ultrastructure of the fossil organic remnants of nacre after decalcification by EDTA, are also found in the samples treated by the CPC method and by chromium sulphate. Continuous membranes, superimposed on the networks, are especially abundant in the material treated by chromium sulphate. It is concluded that the networks of altered trabeculae are not artifacts, but are the representative ultrastructures of the organic remnants of the nacreous layers in the fossils studied so far. It is suggested that disappearance of EDTA soluble substances does not distinctly alter the ultrastructure of the fossil organic residues

On submicroscopic structure of the Nautilus shell

1. The submicroscopic structure of the organic and mineral components of dried shells of Nautilus pompilius LAMARCK and Nautilus macromphalus SOWERBY bas been investigated with the electron microscope.2. Approximately 350 different areas of the shell wall and of the septa, in the living chamber and in the phragmocone. have been studied on positive metallic replicas of original surfaces, of surfaces of fracture, of polished transverse and longitudinal sections, before and after etching with chelating agents. The structure of the organic material has been studied on decalcified fragments of the different regions, thinned by teasing or by disintegration by ultrasonic waves. 3. Various forms of crystals and of crystal aggregates were detected on the outer and inner surfaces of the shell wall and of the camerae. In the crystals lying on the nacreous growth surfaces of the living chamber the tabular hexagonal form (001) (010) (110) of the truncated orthorhombic prism of aragonite is predominant. The c-axis of these crystals is normal to the nacreous stratification. their a-axis, along which many crystals are elongated is predominantly at right angle to the growth lines. Parallel orientation and aggregation. parallel overgrowth of micro-crystals oriented along the a-axis of the basal crystals were recorded in groups of neighbouring crystals but orientation differed in other adjacent groups. Orientation of the crystals with their a-axis parallel to the direction of the trabeculae of the reticulated sheets of conchiolin on which these crystals had developed by epitaxial growth. was observed in some preparations, but was not obvious in others. The present conclusions about the structures of the weathered surfaces will be amended when fresh shells will be available. 4. The membraneous disc or sole interposed in the living chamber between the muscles and the shell wall. is composed of stratified. cleavable layers of thin microfibrils arranged in dense feltings. Near the adoral and adapical ridges of the muscle scars. globular or lenticular microcrystals clustered in considerable numbers are scattered over the surface of this membranous disc and over that of the underlying shell wall, composed of a variety of mother-of-pearl ( helle Schicht). The number of these microcrystals, estimated in several fields, varied between 2 and 126 millions per square millimeter of surface. 5. The surfaces of the concave and of the convex sides of the septa differ greatly in their structure. On the concave side, large, mostly hexagonal tabular crystals ( 001 ) ( 010 ) ( 110 ) , elongated along their a-axis, are lying on the youngest nacreous lamellae and partly embedded in conchiolin sheets. On the convex side, conical or pyramidal structures, composed of stacked discs, are scattered among shreds of the posterior membrane. 6. The posterior membrane which coats the convex side of the septa is composed of microfibrillar layers. 7. The basic mineral structure representative of the porcellaneous substance in the outer layer of the shell wall and in the umbilical callus, consists of mostly elongated, sharp-edged tablets, blades, plates or bars, appearing in transverse or oblique sections, in the form of girders, beams, rods, needles or spindles. These elements are generally assembled in bundles, plates, rows or corpuscles. The composition of these groups, which varies in the different porcellaneous regions, is described. At the border line of porcellaneous and nacreous substances in the shell wall, the elongated elements are predominantly parallel to the c-axis of the nacreous crystals, and normal to the nacreous stratification. An identical disposition was detected along the fringes of porcellaneous substance deeply notched in the neighbouring nacreous substance, in the region of the umbilical callus and in the sutural substances, The organic sheaths interposed between the elongated porcellaneous elements of the outer layer of the shell wall and of the umbilical callus are composed of microfibrils associated with veils. 8. Particularities of structure characterizing the nacreous layers of the shell wall and those of the septa are described. Periodic disturbances in the stratification of the nacreous lamellae consist of variations in the growth along their c-axis and in the orientation of the aragonite crystals involved in the structure of the lamellae. Differences in the crystal shape, size and disposition between the early adapical and ultimate adoral septa reflect differences in the rate of crystal growth of the respective formations. These findings suggest the possibility of extending the physiological and morphological studies of the periodicities in the shell growth to a submicroscopic level. 9. In Nautilus pompilius, the pattern of the lace-like reticulated sheets of nacreous conchiolin of the shell wall is closely similar or identical to that detected previously in Nautilus macromphalus. This pattem of structure of nacreous conchiolin ( « nautiloid pattem » ) found in two of the three surviving species of the living genus Nautilus appears to be a reliable taxonomic character. The septal nacreous conchiolin differs by its tighter texture and by its more slender trabeculae from that of the shell wall. 10. In the areas of junction of the septa and of the inner surface of the wall, the mural and septal nacreous substances are not contiguous. Layers of calcareous substance, with a structure thoroughly different from mother-of-pearl, are interposed in between. These substances, or sutural infillings, include: 1 ) the linear milk-white cements sandwiched between the shell wall and the mural parts of the septa, 2) the extensions of this material which clog the angles of intersection of the wall and of the convex sides of the septa, 3) the calcareous concretions which overlap the angular infillings and protrude into the cameral cavities. These substances, especially the cements, are composed of layers made up of parallel imbricated, elongated crystals, .disposed transversely in the layers, The layers alternate with strands of organic amorphous substance. The elongated crystals are identical to those which characterize the porcellaneous substance. The organic material interposed between these crystals is similarly composed of microfibrils and veils. The calcareous concretions protruding into the cameral cavities are characterized by a disorderly amalgamation of bundles of crystals and of densely stratified sheets of amorphous mineral substance, in which substantial organic matter is embedded. 11. The findings collected with the electron microscope are discussed with reference to particularities of the test configuration in fossil Nautiloidea reported in literature. A comparative study of the sutural infillings of the recent Nautilus shell and .of the cameral deposits of Pseudorthoceras knoxense has revealed close similarities in the structure of these two kinds of sub~ stances. It is assumed that the wedge-shaped plug of calcareous substance which fills the angles of intersection of the shell wall and of the convex sides of the septa in the recent Nautilus might be the morphological equivalent. confined to a restricted area, of the cameral deposits of fossil Nautiloidea

On organic remains in shells of Paleozoic and Mesozoic cephalopods (nautiloids and ammonoids)

Remnants of decalcified nacreous layers from Ordovician, Devonian, Carboneferous (including Pennsylvanian), Permian, Jurassic and Cretaceous, nautiloid and ammonoid shells, examined in the electron microscope, consists of various, biuret-positive structures, which reflect degrees in degradation of the original conchiolon sheets. Identification of these structures as altered nacreous concholin and discrimination from contaminating structures of foreign organisms, a frequent finding in fossil shells, were based on detection of similar structural modifications in the Recent Nautilus shell, in well preserved shells of Pennsylvanian and Mesozoic cephalopods and in alterations produced artificially in experimental diagenesis of the Recent Nautilus shell. Nacreous organic remnants subsisted in recrystallized shells. The mechanism of the conchiolin alterations, the significance of variations in the structural patterns of nautiloid conchiolin, the structural pattern of ammonoid nacreous conchiolin, and modifications in configuration of the nacreous layers in shells with preserved original aragonite and in recrystallized shells, have been discussed

Quantitative MRFM characterization of the autonomous and forced dynamics in a spin transfer nano-oscillator

Using a magnetic resonance force microscope (MRFM), the power emitted by a spin transfer nano-oscillator consisting of a normally magnetized Py$|$Cu$|$Py circular nanopillar is measured both in the autonomous and forced regimes. From the power behavior in the subcritical region of the autonomous dynamics, one obtains a quantitative measurement of the threshold current and of the noise level. Their field dependence directly yields both the spin torque efficiency acting on the thin layer and the nature of the mode which first auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. From the MRFM behavior in the forced dynamics, it is then demonstrated that in order to phase-lock this auto-oscillating mode, the external source must have the same spatial symmetry as the mode profile, i.e., a uniform microwave field must be used rather than a microwave current flowing through the nanopillar

The sustainable materials roadmap

Over the past 150 years, our ability to produce and transform engineered materials has been responsible for our current high standards of living, especially in developed economies. However, we must carefully think of the effects our addiction to creating and using materials at this fast rate will have on the future generations. The way we currently make and use materials detrimentally affects the planet Earth, creating many severe environmental problems. It affects the next generations by putting in danger the future of the economy, energy, and climate. We are at the point where something must drastically change, and it must change now. We must create more sustainable materials alternatives using natural raw materials and inspiration from nature while making sure not to deplete important resources, i.e. in competition with the food chain supply. We must use less materials, eliminate the use of toxic materials and create a circular materials economy where reuse and recycle are priorities. We must develop sustainable methods for materials recycling and encourage design for disassembly. We must look across the whole materials life cycle from raw resources till end of life and apply thorough life cycle assessments (LCAs) based on reliable and relevant data to quantify sustainability. We need to seriously start thinking of where our future materials will come from and how could we track them, given that we are confronted with resource scarcity and geographical constrains. This is particularly important for the development of new and sustainable energy technologies, key to our transition to net zero. Currently 'critical materials' are central components of sustainable energy systems because they are the best performing. A few examples include the permanent magnets based on rare earth metals (Dy, Nd, Pr) used in wind turbines, Li and Co in Li-ion batteries, Pt and Ir in fuel cells and electrolysers, Si in solar cells just to mention a few. These materials are classified as 'critical' by the European Union and Department of Energy. Except in sustainable energy, materials are also key components in packaging, construction, and textile industry along with many other industrial sectors. This roadmap authored by prominent researchers working across disciplines in the very important field of sustainable materials is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the sustainable materials community. In compiling this roadmap, we hope to aid the development of the wider sustainable materials research community, providing a guide for academia, industry, government, and funding agencies in this critically important and rapidly developing research space which is key to future sustainability.journal articl

Balancing, Proportionality, and Constitutional Rights

In the theory and practice of constitutional adjudication, proportionality review plays a crucial role. At a theoretical level, it lies at core of the debate on rights adjudication; in judicial practice, it is a widespread decision-making model characterizing the action of constitutional, supra-national and international courts. Despite its circulation and centrality in contemporary legal discourse, proportionality in rights-adjudication is still extremely controversial. It raises normative questions—concerning its justification and limits—and descriptive questions—regarding its nature and distinctive features. The chapter addresses both orders of questions. Part I centres on the justification of proportionality review, the connection between proportionality, balancing and theories of rights and the critical aspects of this connection. Part II identifies and analyses the different forms of proportionality both in review, as a template for rights-adjudication, and of review, as a way of defining the scope and limits of adjudication