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Ground Pattern (ground + pattern)
Selected AbstractsUltrastructural and immunocytochemical observations of the nervous systems of three macrodasyidan gastrotrichsACTA ZOOLOGICA, Issue 3 2003R. Hochberg Abstract The nervous systems of three macrodasyidan gastrotrichs, Dactylopodola baltica, Macrodasys caudatus and Dolichodasys elongatus, were investigated using immunocytochemistry and electron microscopy. Labelling of neural structures against serotonin revealed the presence of two pairs of cerebral cells, a dorsal cerebral connective, and paired ventral nerve cords in D. baltica. In M. caudatus and D. elongatus serotonin immunoreactivity was present in a single pair of dorsal cerebral cells and the ventral nerve cords; the dorsal connective of D. elongatus was also immunoreactive to serotonin and acetylated ,-tubulin. The presence of paired, serotonin-like immunoreactive cells in D. baltica and other species may represent the plesiomorphic condition in Macrodasyida. The fine structure of the photoreceptors in D. baltica was also investigated to explore the potential ground pattern for eyes in the Macrodasyida. The pigmented photoreceptors of D. baltica contain a unicellular pigment cup, sheath cell and sensory receptor. The pigment cup contains numerous osmiophilic granules that presumably function to shield the eyes from downwelling light in the red part of the spectrum. Projecting into the pigment cup and sheath cell are numerous microvilli from a bipolar sensory cell. A single sensory cell may represent the plesiomorphic condition in Macrodasyida, with multiplication of sensory cells representative of more derived taxa. [source] Slit effect of common ground patterns in affecting crosstalk noise between two parallel signal traces on printed circuit boardsELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 10 2010Tsuyoshi Maeno Abstract It is well known that electromagnetic (EM) disturbances in vehicle-mounted radios are mainly caused by conducted noise currents flowing through wiring harnesses from vehicle-mounted printed circuit boards (PCBs) having common ground patterns with slits. To evaluate the noise current outflows from PCBs of this kind, we previously measured noise current outflows from four types of simple three-layer PCBs having two perpendicular signal traces and different ground patterns with or without slits, and showed that slits on a ground pattern allow conducted noise currents to flow out from PCBs, while the levels for the symmetric slit ground type are smaller than in the case of two asymmetric slit ground types. In the present study, to further investigate the above finding, we fabricated six types of simple two-layer PCBs having two parallel signal traces and different ground patterns with and without slits, and measured the crosstalk noise between the traces. We found that the ground patterns with the slits perpendicular to the traces increased the crosstalk noise levels, which were 19 to 42 dB larger than those for the ground pattern with no slits, while the ground patterns with the slits parallel to the traces were able to reduce the noise levels, which were slightly smaller (by 2.5 to 4.5 dB) than in the case of the no-slit ground pattern. These results were confirmed by FDTD simulation, and were also qualitatively explained by means of an equivalent bridge circuit model that we previously proposed. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(10): 19,24, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10287 [source] Anatomy and ultrastructure of the reproductive organs in Dactylopodola typhle (Gastrotricha: Macrodasyida) and their possible functions in sperm transferINVERTEBRATE BIOLOGY, Issue 1 2008Alexander Kieneke Abstract. The reproductive anatomy of gastrotrichs is well known for several species, especially for the marine taxon Macrodasyida. However, there is little information on the reproductive organs and the modes of mating and sperm transfer in putative basal taxa, which is necessary for accurate reconstruction of the ground pattern of the Gastrotricha. We present the first detailed morphological investigation of the reproductive system of a putative basal gastrotrich, Dactylopodola typhle, using transmission and scanning electron microscopy, histology, and microscopic observations of living specimens. Dactylopodola typhle is a hermaphrodite that possesses paired female and male gonads, an unpaired uterus with an outlet channel that we call the cervix, and an additional accessory reproductive organ, the so-called caudal organ. We hypothesize that the hollow, secretory caudal organ serves for picking up autospermatozoa (self-sperm), for spermatophore formation, and finally for transferring the autospermatophore to a mating partner. The allospermatophore (foreign spermatophore) is stored within the uterus where fertilization occurs. We think that the mature and fertilized egg is released through the cervix and the dorsolateral female gonopore, and not by rupture of the body wall. Based on the morphology, we provide a plausible hypothesis for spermatophore formation and transfer in D. typhle. Preliminary phylogenetic considerations indicate that the stem species of Macrodasyida, perhaps that of all Gastrotricha, had paired ovaries and paired testes, an unpaired uterus, and only one accessory reproductive organ. [source] Ultrastructure of the protonephridial system in Neodasys chaetonotoideus (Gastrotricha: Chaetonotida) and in the ground pattern of Gastrotricha,JOURNAL OF MORPHOLOGY, Issue 7 2007Alexander Kieneke Abstract The taxon Neodasys has a basal position within Gastrotricha. This makes it very interesting for phylogenetic considerations in this group. To complete the reconstruction of the nephridial system in the stem species of Gastrotricha started earlier, we have studied the whole protonephridial system of Neodasys chaetonotoideus by means of complete sets of ultrathin sections and TEM. In many characters, protonephridia of N. chaetonotoideus resemble those of macrodasyidan gastrotrich species. For example, each of the six protonephridia, arranged in three pairs, consists of three distinct cells that constitute the continuous protonephridial lumen. Especially, the terminal cell of the protonephridia of N. chaetonotoideus shows a striking pattern: The perforation of the filter region is a meandering cleft that is continuous with the seam of the enfolded lumen of that cell. With the results presented here and that of former TEM studies, we give a comprehensive idea of the excretory organs in the ground pattern of Gastrotricha. Moreover, we can elaborate on the hypothesized protonephridial system in the stem species of Bilateria. We suggest that a meandering filtration cleft is a feature of the ground pattern of the Bilateria. J. Morphol., 2007. © 2007 Wiley-Liss, Inc. [source] Ultrastructure of the epidermal maxilla II-gland of Scutigera coleoptrata (Chilopoda, Notostigmophora) and the ground pattern of epidermal gland organs in MyriapodaJOURNAL OF MORPHOLOGY, Issue 1 2005Gero Hilken Abstract The epidermal maxilla II-gland of Scutigera coleoptrata was investigated using light and electron microscopy. The glandular epithelium surrounds a spacious integumental cavity at the base of the maxilla II. The gland is formed as a compound gland organ that is composed of thousands of epidermal gland units. Each of them consists of four different cell types: a secretory cell, an accessory or intermediary cell, and a proximal and distal canal cell. The intermediary and the two canal cells form a conducting canal. Only in the most distal part of the intermediary cell is the canal lined by a cuticle. In the area of the two canal cells, the conducting canal is completely covered by a cuticle. The canal passes through the cuticle and opens into the spacious integumental cavity, which serves as a secretion reservoir. The structural organization of the epidermal maxilla II-gland was compared to that of other compound epidermal gland organs in Chilopoda and Diplopoda. All these glandular organs in Myriapoda share the same ground pattern. J. Morphol. © 2005 Wiley-Liss, Inc. [source] Slit effect of common ground patterns in affecting crosstalk noise between two parallel signal traces on printed circuit boardsELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 10 2010Tsuyoshi Maeno Abstract It is well known that electromagnetic (EM) disturbances in vehicle-mounted radios are mainly caused by conducted noise currents flowing through wiring harnesses from vehicle-mounted printed circuit boards (PCBs) having common ground patterns with slits. To evaluate the noise current outflows from PCBs of this kind, we previously measured noise current outflows from four types of simple three-layer PCBs having two perpendicular signal traces and different ground patterns with or without slits, and showed that slits on a ground pattern allow conducted noise currents to flow out from PCBs, while the levels for the symmetric slit ground type are smaller than in the case of two asymmetric slit ground types. In the present study, to further investigate the above finding, we fabricated six types of simple two-layer PCBs having two parallel signal traces and different ground patterns with and without slits, and measured the crosstalk noise between the traces. We found that the ground patterns with the slits perpendicular to the traces increased the crosstalk noise levels, which were 19 to 42 dB larger than those for the ground pattern with no slits, while the ground patterns with the slits parallel to the traces were able to reduce the noise levels, which were slightly smaller (by 2.5 to 4.5 dB) than in the case of the no-slit ground pattern. These results were confirmed by FDTD simulation, and were also qualitatively explained by means of an equivalent bridge circuit model that we previously proposed. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(10): 19,24, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10287 [source] | ||||||||||