scholarly journals The Ligament of the Lucinacea (Eulamellibranchia)

1960 ◽  
Vol s3-101 (53) ◽  
pp. 25-36
Author(s):  
J. A. ALLEN
Keyword(s):  
Outer Surface ◽  
Outer Layer ◽  
Intermediate Stage ◽  
Basic Structure ◽  
Adductor Muscle

The basic structure of the opisthodetic ligament of the Lucinacea consists primarily of inner layer, anterior and posterior outer layers, and periostracum. This is secondarily extended by fused periostracum and fusion layer. Fused periostracum extends as far as the posterior adductor muscle and, except in the Ungulinidae, to the anterior adductor. The fusion layer covers the posterior outer layer and a little beyond. Only in Loripes lucinalis is the fusion layer to be found anteriorly. Below the umbos the inner layer, posterior outer layer, and overlying fusion layer are split. This split can be explained in terms of the growth and form of the shell. The anterior outer layer fills the split and extends to the anterior limit of the lunule. The ligament, external in the Ungulinidae, becomes progressively more internal. At the same time the posterior limit of the outer layer becomes modified as a result of the elongation of the outer surface of the outer mantle fold between the pallial lobes in the depth of the posterior mantle embayment. The Lucinidae are most specialized in this respect where, in L. lucinalis, a tongue of tissue divides much of the ligament horizontally. The Thyasiridae, the remaining family of the group, occupies an intermediate stage in this specialization.

The Lipid Layer: The Outer Surface of the Ocular Surface Tear Film

2001 ◽  
Vol 21 (4) ◽  
pp. 407-418 ◽  
Author(s):  
James P. McCulley ◽  
Ward E. Shine
Keyword(s):  
Water Vapor ◽  
Fatty Acid ◽  
Outer Surface ◽  
Outer Layer ◽  
Tear Film ◽  
Polar Phase ◽  
Lipid Layer ◽  
Water Vapor Transmission ◽  
Aqueous Layer ◽  
Alcohol Composition

The outer layer of the tear film—the lipid layer—has numerous functions. It is a composite monolayer composed of a polar phase with surfactant properties and a nonpolar phase. In order to achieve an effective lipid layer, the nonpolar phase, which retards water vapor transmission, is dependent on a properly structured polar phase. Additionally, this composite lipid layer must maintain its integrity during a blink. The phases of the lipid layer depend on both lipid type as well as fatty acid and alcohol composition for functionality. Surprisingly, the importance of the composition of the aqueous layer of the tear film in proper structuring of the lipid layer has not been recognized. Finally, lipid layer abnormalities and their relationship to ocular disease are beginning to be clarified.

scholarly journals The ligament of Cochlodesma praetenue (Pulteney)

1960 ◽  
Vol 39 (3) ◽  
pp. 445-447 ◽  
Author(s):  
J. A. Allen
Keyword(s):  
Outer Surface ◽  
Basic Structure ◽  
Inner Surface

In a recent paper (Allen, 1958) the ligament of Cochlodesma praetenue (Pulteney) as shown to have unusual features, the significance of which was not appreciated at that time. Examination of its structure shows that a further description is necessary.Studies by Owen, Trueman & Yonge (1953), Owen (1958,1959), and Yonge (1953, 1957) have made clear the basic structure of the ligament of the adult bivalve. Primarily the ligament is composed of an inner layer covered by the anterior andposterior outer layers and the periostracum. The inner layer is secreted by the epithelium of the mantle isthmus, the outer layers are secreted by the outer surface of the outer mantle fold within the depths of the mantle embayments at either end of the mantle isthmus, and the periostracum is secreted by the inner surface of the outer mantle fold. This primary ligament may be secondarily extended anteriorly and/or posteriorly by fusion of the mantle margins and may involve extension by periostracum, or extension by fusion layer.

Fine structure of the tubes of Maldanidae (Annelida)

2017 ◽  
Vol 97 (5) ◽  
pp. 1177-1187 ◽  
Author(s):  
Tatiana D. Shcherbakova ◽  
Alexander B. Tzetlin ◽  
Maria V. Mardashova ◽  
Olga S. Sokolova
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fine Structure ◽  
Outer Layer ◽  
Basic Structure ◽  
Tube Surface ◽  
3D Network ◽  
Sediment Particles ◽  
Scanning Electron

Many marine annelids are active tube builders. Several polychaete families make agglutinated tubes by fixing sediment particles with specific secretions from their epithelial glands. The fine structure of the tubes of six species of Maldanidae from five genera (Nicomache minor, N. lumbricalis, Maldane sarsi, Praxillella praetermissa, Axiothella catenata, Rhodine gracilior) was examined by scanning electron microscopy. These species exhibit different lifestyles. Nicomache minor and N. lumbricalis inhabit massive hard tubes attached to stones. Other species live in the sediment, Rhodine in rigid organic tubes, Praxillella, Axiothella and Maldane in sand or mud tubes. All the examined maldanid tubes have a similar basic structure. The inner sheath of the tubes is made of a hardened organic lining secreted by the worm. Fibres from the inner sheath fasten sediment particles of the agglutinated layer. In Nicomache the tube surface is covered with a fibrous outer layer. All tube layers contain variously arranged organic fibres, which form a 3D network in the agglutinated layer and fabric-like linings in the inner sheath and outer layer. The tubes of Maldanidae may be important for taxonomy, and useful for identification of fossils.

New species of Macoma (Bivalvia: Tellinoidea: Tellinidae) from southeastern Brazil, and with description of its gross anatomy

Zootaxa ◽  
2005 ◽  
Vol 1012 (1) ◽  
pp. 13 ◽  
Author(s):  
ELIANE P. ARRUDA ◽  
OSMAR DOMANESCHI
Keyword(s):  
Outer Surface ◽  
Gross Anatomy ◽  
Adductor Muscle ◽  
Southeastern Brazil ◽  
Similar Species ◽  
Northern Coast ◽  
Western Atlantic ◽  
Left And Right ◽  
Anatomical Characters ◽  
The Right

Macoma biota n. sp. is described from material collected in the intertidal zone of Praia da Cidade, Caraguatatuba Bay on the northern coast of the state of São Paulo, Brazil. The species is characterized by its shell features and gross anatomy. The western Atlantic M. constricta (Bruguière, 1792) is the most similar species to M. biota, both hardly distinguishing by their shell characteristics. The main shell feature distinguishing M. biota from M. constricta is the ventral limb of the pallial sinus that is shorter, steeper and confluent with the pallial line along the first quarter of this scar in M. biota, and long, closely parallel to and confluent with the pallial line far posteriorly in M. constricta. Anatomical characters distinguishing M. biota are: ventral channel formed by asymmetrical left and right additional mantle folds; paired, asymmetrical siphonal organs; all four labial palps provided of short conical papillae on their outer surface and simple, acute terminal tip; both demibranchs equally long; and presence of a single short, stout “accessory adductor muscle” adjacent to the cruciform muscle. Macoma constricta has ventral channel formed by the right additional mantle fold only; unpaired, left siphonal organ; all four labial palps lacking papillae on their outer surface and terminal tip of the left inner labial palp produced into a thin sheath with undulated plicae; inner demibranch longer and extending beyond the antero-dorsal limit of the outer demibranch; and “accessory adductor muscle” absent.

Investigation of Properties of Coated Hollow Mini-Spheres

2019 ◽  
Vol 799 ◽  
pp. 26-30
Author(s):  
Viktors Mironovs ◽  
Alexey Tatarinov ◽  
Ervins Blumbergs ◽  
Irina Boiko
Keyword(s):  
Electrical Conductivity ◽  
Adsorption Capacity ◽  
Outer Surface ◽  
Outer Layer ◽  
Cellular Structures ◽  
Light Weight ◽  
Structured Materials ◽  
Low Weight ◽  
Lower Porosity ◽  
High Level

Metal hollow mini-spheres (MHMS) present a basis for the creation of new structured materials due to their low weight and energy adsorption capacity. Typically, MHMS are made of steel with a high level porosity in the sphere’s wall 80-110 microns thick. Modification of the outer surface by copper coating of 20-30 microns imposed by vacuum sputtering provides several times higher electrical conductivity, lower porosity of the outer layer and smoother surface, preserving light weight and flotation properties. This modification will provide better possibilities for spheres’ consolidation by means of sintering and electric brazing and creation of new cellular structures.

scholarly journals Memoirs: Note on Eggs and Embryos of the South African Myxinoid, Bdellostoma (Heptatretus) hexatrema, Müll

1918 ◽  
Vol s2-63 (249) ◽  
pp. 141-159
Author(s):  
J.D. F. GILCHRIST
Keyword(s):  
South African ◽  
Outer Surface ◽  
Outer Layer ◽  
General Structure ◽  
Lower Surface ◽  
The Body ◽  
The South ◽  
Early Stages ◽  
Definite Structure ◽  
Excretory Organs

(1) Five naturally deposited eggs of the Cape Bdellostoma have been found, two containing well-advanced embryos. (2) The eggs are larger than those of other species, the anchor-filaments are shorter, and there are two polar rings. (3) The general structure of the shell is similar to that described for other species, and there are numerous small projections on its surface, as in some species. These consist of the columns of the columnar layer modified at the apex of the projection. (4) There are numerous small fissures in the shell, probably respiratory apertures. (5) The polar rings have a definite structure, differing from that of the rest of the shell, in that the inner layer becomes greatly enlarged, and the outer layer much reduced. (6) The anchor-filaments are not homogeneous in their structure, but consist of all the layers of the shell, the chief modification being that the heads of the columns of the columnar layer becomes drawn out so as to appear as striations. (7) The anchors' consist of the modified columnar layer and the stratified layer. On their outer surface the heads of the columns of the columnar layer appear as disconnected dark dots, while their lower surface consists of the same elements as the surface of the filament. (8) In the embryo the segmental duct occurs at the distal end of the last tubule of the pronephros, but, though having a lumen, does not open into it. It is found also at the distal end of the second last tubule, where, however, it becomes solid, and disappears. It was not found extending further into the pronephros. (9) The tubules of the mesonephros are not strictly segmentally arranged, in that there are six tubules in three segments of the body behind the pronephros, though there is one tubule for each succeeding segment, as far as the mesonephros extends. I am greatly indebted to Prof. Bashford Dean for his generous assistance in literature on the early stages of Bdellostoma and allied subjects. As a pioneer in this work, he is deeply interested in the finding of the eggs of the Cape Bdellostoma. Prof. Price has also kindly sent me reprints of his important papers on the development of the excretory organs. I have also to express my obligations to Mr. P. MacManus, who has redrawn for me figs. 2 and 10.

scholarly journals Constructional morphology of the shell/ligament system in opisthogyrate rostrate bivalves

2015 ◽  
Vol 106 (4) ◽  
pp. 221-227 ◽  
Author(s):  
J. Echevarría ◽  
S. E. Damborenea ◽  
M. O. Manceñido
Keyword(s):  
Tensile Stress ◽  
Outer Layer ◽  
Adductor Muscle ◽  
Dorsal Margin ◽  
Fibrous Layer ◽  
Lever System ◽  
Constructional Morphology ◽  
Dorsal Ridge ◽  
Lamellar Layer

ABSTRACTThe bivalve ligament provides the thrust for shell opening, acting as the resistance in a lever system against which adductor muscle effort is applied. Usually, its outer lamellar layer is subjected to tensile stress, while the inner fibrous layer is compressed, with the pivotal axis located between them. However, opisthogyrate rostrate bivalves display a concave dorsal margin, and both the umbo and the postero-dorsal angle of the shell project dorsally to the ligament, which then fails to act as pivotal axis. Three opisthogyrate rostrate genera of unrelated lineages show somewhat different solutions to this morpho-functional challenge. In Cuspidaria (Anomalodesmata), the ligament is internal, subjected only to compression and ventral to the pivotal axis, a thickened periostracum develops, forcing the dorsal margins of the valves to act as pivotal axis, and the posterior parts of the shell's dorsal margins gape dorsally. In Nuculana (Palaeotaxodonta), the inner layer of the ligament is internal, the outer layer is external but reduced, and some species develop a dorsal ridge parallel to the commissural plane, on a level with the rostrum and acting as pivotal axis. In Pterotrigonia (Palaeoheterodonta) and other rostrate trigoniides, the ligament is external opisthodetic, but is allometrically reduced. Trigoniides may also develop a dorsal ridge.

scholarly journals ABOUT THE FEATURES OF THE PROCESS OF CIRCULAR PLASTIC COMPRESSION STRANDS

2020 ◽  
pp. 41-46
Author(s):  
L. M. Gurevich ◽  
V. F. Danenko
Keyword(s):  
Plastic Deformation ◽  
Outer Surface ◽  
Outer Layer ◽  
Plastic Compression ◽  
Local Areas ◽  
Selective Formation

A simulation of the process of circular plastic compression of a strand of construction 1+6 by stretching in four pairs of rollers is carried out. It is established that the wires of the outer layer of the strand swell before entering the first pair of rollers, as well as selective formation of local areas of sharply increased plastic deformation on the outer surface of the wires.

Solar Filaments as Tracers of Subsurface Processes

2000 ◽  
Vol 179 ◽  
pp. 177-183
Author(s):  
D. M. Rust
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Coronal Mass Ejections ◽  
Interplanetary Space ◽  
Intermediate Stage ◽  
Coronal Plasma ◽  
Magnetic Helicity ◽  
The Sun ◽  
New Paradigm ◽  
Solar Filaments

AbstractSolar filaments are discussed in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of coronal plasma into magnetic fields that are twisted or dimpled as a consequence of motions of the fields’ sources in the photosphere. According to a new paradigm, filaments form in rising, twisted flux ropes and are a necessary intermediate stage in the transfer to interplanetary space of dynamo-generated magnetic flux. It is argued that the accumulation of magnetic helicity in filaments and their coronal surroundings leads to filament eruptions and coronal mass ejections. These ejections relieve the Sun of the flux generated by the dynamo and make way for the flux of the next cycle.

A scanning electron microscopic study on dissolving process of cholesterol gallstones by chenodeoxycholic acid (CDCA)

1978 ◽  
Vol 36 (2) ◽  
pp. 522-523
Author(s):  
T. Kanetaka ◽  
M. Cho ◽  
S. Kawamura ◽  
T. Sado ◽  
K. Hara
Keyword(s):  
Electron Microscope ◽  
Chenodeoxycholic Acid ◽  
Outer Surface ◽  
Electron Microscopic ◽  
Cholesterol Gallstones ◽  
The Core ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Acceleration Voltage ◽  
Scanning Electron

The authors have investigated the dissolution process of human cholesterol gallstones using a scanning electron microscope(SEM). This study was carried out by comparing control gallstones incubated in beagle bile with gallstones obtained from patients who were treated with chenodeoxycholic acid(CDCA).The cholesterol gallstones for this study were obtained from 14 patients. Three control patients were treated without CDCA and eleven patients were treated with CDCA 300-600 mg/day for periods ranging from four to twenty five months. It was confirmed through chemical analysis that these gallstones contained more than 80% cholesterol in both the outer surface and the core.The specimen were obtained from the outer surface and the core of the gallstones. Each specimen was attached to alminum sheet and coated with carbon to 100Å thickness. The SEM observation was made by Hitachi S-550 with 20 kV acceleration voltage and with 60-20, 000X magnification.

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