Search results for "Surface anatomy"

Zur deutung der sogenannten a-orientierung in polyäthylenterephthalat

1976

Bei der Kristallisation von schwach orientierten Polyathylenterephthalat-Folien erhalt man eine Struktur, fur die in der Rontgenweitwinkelstreuung der 100-Reflex am Meridian und der 010-Reflex am Aquator liegt. Die Rontgenkleinwinkelstreuung zeigt ein Intensitatsmaximum am Meridian. Man kann diese Befunde mit einem Modell aus tordierten Lamellen erklaren, deren Torsionsachsen bevorzugt senkrecht zur Verstreckrichtung liegen. In einer solchen tordierten Lamelle liegen die (001)-Ebenen der Kristallite parallel zur Lamellenoberflache und die b-Achsen in Richtung der Torsionsachse. Die bei dieser Struktur auftretende negative Doppelbrechung kann mit diesem Modell ebenfalls erklart werden. By cr…

Bio-sintering processes in hexactinellid sponges: Fusion of bio-silica in giant basal spicules from Monorhaphis chuni☆

2009

The two sponge classes, Hexactinellida and Demospongiae, comprise a skeleton that is composed of siliceous skeletal elements (spicules). Spicule growth proceeds by appositional layering of lamellae that consist of silica nanoparticles, which are synthesized via the sponge-specific enzyme silicatein. While in demosponges during maturation the lamellae consolidate to a solid rod, the lamellar organization of hexactinellid spicules largely persists. However, the innermost lamellae, near the spicule core, can also fuse to a solid axial cylinder. Similar to the fusion of siliceous nanoparticles and lamella, in several hexactinellid species individual spicules unify during sintering-like processe…

Comparative study of the three attachment mechanisms of diplectanid monogeneans

2011

Abstract One of the main characteristics of the monogenean family Diplectanidae Monticelli, 1903 is their complex haptor formed by 2 pairs of hooks, transversal bars, 14 peripheral marginal hooks, and accessory adhesive organ (lamellodisc or squamodisc) that can be present or absent. Sub-family Lamellodiscinae Oliver, 1969 presents one or two lamellodiscs, formed by several overlapped lamellar esclerites (lamellae) which are piled up. Species like Furnestina echeneis only have one large ventral lamellodisc. This organ function has been categorized in different ways (i.e. accessory adhesive organ, supplementary or compensating disc or sucker), although its real mode of operation and function…

Fibularis tertius muscle in women & men: A surface anatomy cross-sectional study across countries

2019

The fibularis tertius muscle (FTM) is a rare anatomic variation. The prevalence of this exclusively human structure, which is found in the anterior compartment of the leg, is often underestimated, and it is believed that foot and ankle conditions are more difficult to manage in patients with an FTM. The aim of this study was to assess the presence of the FTM palpation and determine whether its presence is associated with an individual’s sex, because the exact prevalence in males and females is unclear. An observational cross-sectional study was carried out. The study included 481 people (23.49% men and 76.51% women) with a mean age of 23.51±5.369 years, who were recruited from a Podiatric M…

On the formation of lamellae during annealing of extended chain crystals of radiation-polymerized trioxane

1969

Abstract The structure changes of radiation-polymerized trioxane taking place during annealing have been studied by means of electron microscopy, X-ray small- and wide-angle scattering, and differential thermal analysis. The original fibrillar crystals, supposedly consisting of extended chains, change into lamellar crystals due to annealing at temperatures between 150° and 190°C. Lamella formation can be connected with the appearance of a long period of about 200A which is not observed in the unannealed sample. During annealing within the same temperature range the X-ray reflections due to the twin structure of the original polytrioxane disappear, whereas the orientation of the fraction wit…

Correlations between transmural mechanical and morphological properties in porcine thoracic descending aorta.

2015

Determination of correlations between transmural mechanical and morphological properties of aorta would provide a quantitative baseline for assessment of preventive and therapeutic strategies for aortic injuries and diseases. A multimodal and multidisciplinary approach was adopted to characterize the transmural morphological properties of descending porcine aorta. Histology and multi-photon microscopy were used for describing the media layer micro-architecture in the circumferential-radial plane, and Fourier Transform infrared imaging spectroscopy was utilized for determining structural protein, and total protein content. The distributions of these quantified properties across the media thi…

A Theoretical Model for Excitation Energy Transfer in Chlorosomes: Lamellar and Rod-Shaped Antenna Structures

2008

A model based on exciton theory is presented for description of excitation energy transfer in chlorosomes. Three models to describe the internal organization of the pigments inside the chlorosome were considered, a stack of single-wall rods, a stack of double-wall rods and a stack of lamellae directed along the long axis of the chlorosome. Simulated absorption, circular dichroism and linear dichroism spectra of single-wall rod and the lamella structures turned out to be practically identical. It was shown that rod—rod interactions may localize the exciton states in the regions of a rod facing a neighboring rod. Such localized states provide a fast excitation energy transfer mechanism in per…

2019

Lamella-forming ABC triblock terpolymers are convenient building blocks for the synthesis of soft Janus nanoparticles (JNPs) by crosslinking the B domain that is “sandwiched” between A and C lamellae. Despite thorough synthetic variation of the B fraction to control the geometry of the sandwiched microphase, so far only Janus spheres, cylinders, and sheets have been obtained. In this combined theoretical and experimental work, we show that the blending of polybutadiene homopolymer (hPB) into lamella morphologies of polystyrene-block-polybutadiene-block-polymethylmethacrylate (SBM) triblock terpolymers allows the continuous tuning of the polybutadiene (PB) microphase. We systematically vary …

NanoSIMS: insights into the organization of the proteinaceous scaffold within Hexactinellid sponge spicules.

2010

The giant basal spicules (GBS) from Monorhaphis chuni (Porifera [sponges], Hexactinellida) represent the largest biosilica structures on Earth and can reach lengths of 300 cm (diameter of 1.1 cm). The amorphous silica of the inorganic matrix is formed enzymatically by silicatein. During this process, the enzyme remains trapped inside the lamellar-organized spicules. In order to localize the organic silicatein scaffold, the inside of a lamella has been analyzed by nano-secondary ion mass spectrometry (NanoSIMS). It is shown that the GBSs are composed of around 245 concentrically arranged individual siliceous lamellae. These surround an internal siliceous axial cylinder. The lamellae adjacent…

Apposition of silica lamellae during growth of spicules in the demosponge Suberites domuncula: Biological/biochemical studies and chemical/biomimetic…

2006

Recently it has been discovered that the formation of the siliceous spicules of Demospongiae proceeds enzymatically (via silicatein) and occurs matrix guided (on galectin strings). In addition, it could be demonstrated that silicatein, if immobilized onto inorganic surfaces, provides the template for the synthesis of biosilica. In order to understand the formation of spicules in the intact organism, detailed studies with primmorphs from Suberites domuncula have been performed. The demosponge spicules are formed from several silica lamellae which are concentrically arranged around the axial canal, harboring the axial filament composed of silicatein. Now we show that the appositional growth o…