External Ribs Research Articles

Changes in Hydraulic Roughness Coefficients for Circumferentially Strained M294 Pipe

When a culvert or storm drainage pipe is being sized on the basis of discharge capacity requirements, knowledge of the hydraulic roughness of the pipe is required. Hydraulic roughness is typically influenced by both the roughness of the pipe material and the inside pipe wall profile (e.g., smooth, corrugated, etc.). When subjected to external loads associated with field installations (e.g., backfill, compaction, etc.), the inside wall profile of thermal-plastic pipe products, like high-density polyethylene (HDPE) M294 drainage pipe, often changes due to circumferential strain. As lined HDPE pipe strains circumferentially, the structural external ribs reduce in diameter, which causes the inside liner to develop a longitudinal corrugated wall profile. Variations in the hydraulic roughness of M294 Type S drainage pipe with 24-in. (0.61-m) diameter that were based on external circumferential strain rates ranging from approximately 0 to 2.4% were identified in this study, conducted at the Utah Water Research Laboratory, Utah State University. The circumferentially strained pipe wall geometries of four in-service M294 Type S drainage pipes with 24-in. (0.61-m) diameter were measured and compared with the laboratory pipe conditions. The results of this study were also compared with a previously published predictive method for determining Manning's n values on the basis of corrugation depth and pipe diameter.

Ultrastructure of the Miracidium of Echinostoma paraensei Lie and Basch, 1967 (Trematoda, Echinostomatidae)

The morphology of Echinostoma paraensei was studied using transmission electron microscopy. The terebratorium region has many electrondense secretory granules and many folds on the surface. The epidermal cells that cover the larval body have unique nuclear morphology, many mitochondria and vesicles being attached to the interepidermal ridges by a septate junction. The cilia present the organization 9 + 2 and a typical structure with a shaft, axosome, basal body and rootlet. Below the epidermal cells there is a layer of circular muscle and, adjacent to it, a layer of longitudinal muscle fibers. The excretory system has two flame cells, with internal and external ribs and leptotriches at the barrel region, an excretory vesicle and an excretory pore.

Palaeocarpinus dakotensissp.n. (Betulaceae: Coryloideae) and Associated Staminate Catkins, Pollen, and Leaves from the Paleocene of North Dakota

Palaeocarpinus dakotensis Manchester, Pigg, et Crane sp.n. (Coryloideae, Betulaceae) is described from the Late Paleocene Almont and Beicegel Creek floras of North Dakota based on infructescences with associated staminate catkins, pollen, and leaves. The well‐preserved, silica‐permineralized specimens provide both anatomical and morphological data for this widely distributed genus of the Northern Hemisphere Paleogene. Characters that were previously unknown for the genus are described from anatomically preserved specimens, supporting earlier suggestions that Palaeocarpinus combines features found separately in the extant Coryleae and Carpineae. Features of Coryleae include infructescences composed of cymes with paired nuts, each enclosed within two highly dissected bracts of equal size quite similar to those of some species of modern Corylus, and staminate catkins with four to six bifurcate stamens per bract. Similarly, there are four bifurcate stamens per bract in extant Corylus and four to six in Ostryopsis, whereas more numerous stamens are found in Carpinus and Ostrya. Other features, however, are characteristic of the Carpineae, including external longitudinal ribs on bracts, many fruits per infructescence, and small, ribbed nuts with vascular bundles lying outside the endocarp. Pollen from the stamens of associated catkins is triporate with a scabrate exine and apparently lacks opercula on the apertures, as in Corylus. Simple, cordate‐based elliptical leaves with pinnate, craspedodromous secondary veins and serrate margins referred to Corylites sp. are also found in association and are thought to represent the same coryloid plant. The appearance of Palaeocarpinus in the fossil record apparently predates that of extant genera in the Coryloideae, and it is likely that Palaeocarpinus‐like plants were the forerunners of both Coryleae and Carpineae.

Soritidés éocènes à costulation et/ou lames sous-épidermiques discrètes : les genres Spirolina, Praerhapydionina et Paraspirolina n. gen. dans le « Faciès à imperforés de l'Éocène moyen à supérieur de Grèce

In the Gavrovo-Tripolitza zone of Greece, the «Faciès à imperforés indicates a peculiar back-reef to lagoonal sedimentation episode succeeding a bauxitogenous emersion. The foraminiferal association comprises several arenaceous conical taxa, a lot of miliolids, a species close to Praebullalveolina afyonica, various Peneroplis and/or Dendritina, Spirolina and Praerhapydionina species, scarce small Orbitolites and Rhabdorites malatyaensis. The similarity of this association with others from various parts of the Tethyan area gives evidence for a generalized regressive episode linked to the terminal Middle Eocene tectonic phase. From this association, presence of a new taxon is emphasized : Paraspirolina gigantea n. gen., n. sp. is characterized by an external aspect of a large Spirolina, a single dendritic terminal aperture and the very unusual association of external ribs with sub-epidermal partitions. Both of these last features appearing as independent adaptive devices related to algal symbiosis, their conjunction seems to characterized a singular evolutionary grade in a particular lineage. A single terminal aperture, together with a common tendency to develop an uniserial evolute rectilinear final part (PRU) seems to show a link between the new taxon, several Eocene soritids of the Old World, namely various Spirolina species (devoid of sub-epidermal partitions) and various species assigned to Praerhapydionina (with sub-epidermal partitions, one of them, P. huberi, being reported as ribbed); they are thought to constitute a natural group (a plexus or a sub-family).

Ultrastructure of the developing protonephridial system of the cercaria of Philophthalmus sp. (Trematoda, Digenea).

The fully developed flame bulb of Philopthalmus exhibits the structure characteristic of Trematoda and Monogenea: external and internal ribs forming a weir, external and internal leptotriches, and two longitudinal cytoplasmic cords connected by a septate junction. The proximal canal has a septate junction and surface lamellae. In developing cercariae, perikarya of terminal and proximal canal cells are close together, and sheet-like outgrowths of the terminal cell are externally surrounded by cytoplasm of the proximal canal cell containing a septate junction. Internal outgrowths and external cytoplasm are connected by many "membranes", i.e. desmosome-like structures. Internal sheets break up into internal ribs, and the external cytoplasm breaks up into external ribs, external and internal ribs connected by the filtration "membrane". The developing distal excretory duct possesses a septate junction and many branching and looping lamellae. A comparison of Philopthalmus with the cestode Austramphilina elongata, the only other platyhelminth species in which the development of the protonephridia has been studied at the ultra-structural level, revealed that the two species differ in the presence and absence, respectively, of a septate junction in the flame bulb at an early stage of development.

Ultrastructure of the flame bulbs and protonephridial capillaries ofRugogaster hydrolagi(Platyhelminthes, Trematoda, Aspidogastrea)

The ultrastructure of the terminal apparatus and protonephridial capillaries of R. hydrolagi is described. The weir of the flame bulb consists of alternating rows of ribs connected by a membrane of extracellular matrix. Internal ribs, internal leptotriches and cilia of the flame are continuous with the terminal cell, the perikaryon of which lies basal to and alongside the weir. External ribs, external leptotriches and a pair of cytoplasmic cords along the weir are continuous with the proximal canal cell. Distally, some ciliary membranes extend beyond the end of the microtubules but do not enter the cytoplasm. The distal half of the flame is surrounded by cytoplasm of the proximal canal cell with many electron dense inclusions. The lumen of proximal capillaries is relatively smooth, but in more distal capillaries the lumen surface is enlarged by increasing numbers of lamellae, and lateral flames are present. The phylogenetic position of Rugogastridae is discussed.

Ultrastructure of the protonephridial system of Dactylogyrus sp. and an unidentified ancyrocephaline (Monogenea: Dactylogyridae)

The ultrastructure of the flame bulbs and capillaries of the protonephridia of Dactylogyrus (probably anchoratus) from Carassius auratus in southeastern Australia, and of an unidentified ancyrocephaline from the marine teleost Priacanthus macracanthus in southern Queensland is described. The cilia of the flame are anchored in the terminal cell by means of basal bodies without distinct rootlets. The nucleus of the terminal cell is basal, and (in Dactylogyrus) partly lateral to the basal bodies. The weir consists of a row of internal and a row of external ribs (rods) connected by a ‘membrane’. The external ribs are continuations of the cytoplasm of a thick-walled ‘cytoplasmic cylinder’ (proximal canal cell) which tightly surrounds most of the flame and contains a septate junction; the internal ribs are continuous with the terminal cell. Internal leptotriches arise from the perikaryon of the terminal cell, and, in the ancyrocephaline, also from the internal ribs. The wall of the protonephridial capillaries contains a septate junction, a reticulum of interconnected spaces and, in the ancyrocephaline, also lamellae. Lateral flames are common in the capillaries of Dactylogyrus.

Ultrastructure of the flame bulbs of the Monopisthocotylean MonogeneaLoimosina wilsoni(Loimoidae) andCalceostoma herculanea(Calceostomatidae)

The flame bulbs of Loimosina and Calceostoma consist of a row of external and a row of internal longitudinal ribs connected by a « membrane » apparently of extracellular matrix, and two cytoplasmic cords connected by a septate junction. Internal ribs are continuous with the terminal cell, external ribs and cytoplasmic cords with the proximal canal cell. Both species have many internal leptotriches, in the first, some external leptotriches were also seen. Internal leptotriches arise from the perikaryon of the terminal cell or the internal ribs. The flame bulbs closely resemble those of the Monogenea Polyopisthocotylea examined and of Gyrodactylus, Dactylogyrus and an unidentified ancyrocephaline, i. e. evidence available indicates that all Monogenea share one type of flame bulb, also found in aspidogastreans and digeneans, but different from that of gyrocotylids, amphilinids and cestoideans. Udonella has a different type of flame bulb and, therefore, is unlikely to be a monogenean.

FRUSTULAR MORPHOLOGY AND TAXONOMIC AFFINITIES OF NAVICULA COMPLANATOIDES (BACILLARIOPHYCEAE)1

ABSTRACTLive and prepared cells of the marine pennate diatom Navicula complanatoides Hust. were examined with light and electron microscopy. It has narrowly lanceolate valves (26–55 μm long, 4–5 μm wide) and girdles 10–24 μm in depth. Striae are parallel at the center of the valve (24–28 in 10 μm), becoming slightly convergent toward the apices.Electron microscopy revealed that the external valve surface presents a longitudinally ribbed appearance (20–28 parallel ribs at its maximum width), whereas internally, rectangular areolae are occluded by ricae. The raphe slit lies in a narrow axial area, and one side of the raphe sternum is deeper and folds over the other, obscuring the internal opening. Internally, the central virga on one side of the raphe and two virgae on the other are somewhat broader. A conspicuous pore (stigma) is present between the two broadened virgae.The girdle consists of valvocopulae, copulae, and pleurae. There are 16–20 bands per cingulum. The valvocopulae and copulae are hollow tube‐like structures, with inner and outer portions contrsting in morphology. They decrease in diameter in an abvalvar direction. There are four pleurae. These are flat bands which facilitate overlap of the epicingulum and hypocingulum.Fundamental features of the valve and girdle reveal the distinctness of this species within Navicula. The areolae, external longitudinal ribs, and raphe structure suggest affinities with Pleurosigma, Gyrosigma, and Haslea. It is hypothesized that they share a derived state which indicates a recent common ancestor for these taxa. N. complanatoides and related species of the Naviculae microstigmatacae are distinctive enough to merit their own genus within the Naviculaceae.

Development of the protonephridia of Austramphilina elongata

In embryos of Austramphilina elongata, ciliary tufts (flames) of three terminal cells are enclosed by cytoplasmic cylinders of a single, proximal canal cell. The cylinders are joined to form a single capillary, connected to the capillary of the distal canal cell by a desmosome. Internal outgrowths of the terminal cells grow into the space between the cylinders and the outermost cilia. During development, more cilia are formed, the parts of the cylinders closest to the terminal cells bulge out to accommodate the additional cilia, and at points of contact between the inner outgrowths and the cylinders external ribs are formed, connected to the internal ribs formed from the inner outgrowths by means of thin, cytoplasmic sheaths (“membranes”). During development and in fully developed protonephridia, the cytoplasmic cylinders are connected to the terminal cells by desmosomes but do not fuse with them.

Boundary-Layer Development on a Circular Cylinder With Ribs

An integral method for the calculation of the boundary layer development on a circular cylinder with external meridional ribs is presented. The calculation method, which takes into account the effect of the ribs on the laminar and turbulent boundary layers and on transition, gives results which are in qualitative agreement with experimental data. Analytical results obtained with this method shed some light on the influence of rib roughness on boundary-layer development and support earlier arguments and conclusions derived from experimental data on the effect of external ribs or stakes on the mean flow around rounded structures at large Reynolds numbers.

Ultrastructure of the protonephridial system of Polystomoides malayi Rohde and P. renschi Rohde (Monogenea: Polystomatidae)

Rohde K. 1973. Ultrastructure of the protonephridial system of Polystomoides malayi Rohde and P. renschi Rohde (Monogenea : Polystomatidae). International Journal for Parasitology 3: 329–333. Polystomoides malayi and P. renschi have three types of protonephridial flames. The first type is a typical flame cell with internal and external ribs connected by a weir membrane without nephrostomes, and with internal and external leptotriches. The second type is a flame cell complex consisting of at least two flames reaching into a common cavity. The third type is a non-terminal (= lateral) flame in the protonephridial ducts, consisting of loosely arranged cilia many of which have lateral tube-like extensions and whose tips have irregularly arranged filaments gradually decreasing in number. The number of cilia in all types of flames varies. The smallest capillaries are strongly convoluted and have a smooth or slightly reticulated surface, the larger ducts have strongly reticulated walls and single cilia may be found in the cavities of the reticulum.

Hydromechanical complex at Serebryansk No. 1 Hydroelectric station

1. The hydraulic testing of the turbine penstock permitted the elimination of several defects detected in its shell. Of the two types of bulkhead flanges used in the tests, the erection of the plane flange is considerably simpler. 2. The installation of a drain ahead of each line of the penstock permits the water leaking through the gate seals, when the gate is closed, to be intercepted and discharged through outlet pipes into a ditch. The use of such drains can be recommended at similar hydroelectric stations. 3. Because the removal of the internal bracing of the transition chambers in the penstocks was carried out by oxygen flame cutting, which causes local heating of the lining and its peeling away from the concrete, the number of braces should be reduced to a minimum and external ribs of sufficient stiffness adopted instead. 4. In addition to by-pass pipes connecting the draft-tube chambers, it is also desirable to provide pipes for the direct communication of the draft tubes to the tailwater, for the equalizing of water levels before raising a maintenance gate, regardless of whether or not there is water in the other pipes.

Cubierta de doble curvatura de cables pretensados (Finlandia)

A new ice hockey stadium has been built in Tampere, Finland. It has a reinforced concrete structure and a light, double curvature, roof suspended from a network of prestressed cables. It has a rectangular planform, 63x92 m, and it can accommodate 10,000 spectators. The hockey rink is in the centre. After a brief comparison of various types of suspended roofs, the author describes his own design, and discusses the most delicate aspects of the project. The cables are anchored in lateral arched beams, whose stability is provided by external prestressed concrete ribs. The author emphasizes the importance of these beams for the overall efficiency of the project. Special care was taken to avoid curvature of the cables where these penetrate into the lateral beams, without, however, restricting the freedom of the cables to oscillate. The article describes the placing of the cables, the details of the cables themselves, and their stretching: all of which is a technology that is now well know and tried.