Linear Rows Research Articles

The role of spatio-temporal patch connectivity at the landscape level: an example in a bird distribution

The recent development of landscape ecology emphasizes the importance of connectivity for population viability. Landscape connectivity is the degree to which the landscape facilitates or impedes movement among resource patches. Most of the empirical data identifying landscape spatial patterns (connectedness) that interfere with individual movements, concern walking animals with low powers of dispersal. For flying animals, the distance between patches is measured in almost all cases using euclidean distance. This does not account for the behavioural characteristics of species that depend on landscape patterns for their movements. We hypothesized that the presence of Short-toed Tree Creeper ( Certhia brachydactyla) depends on landscape spatial structure, so we tested it in two contrasting rural landscapes. These adjacent landscapes differ in grain size, the quality of linear landscape elements delimiting fields, and their history. In the recently reclaimed polder, Tree Creepers are only present in linear rows of trees with a high degree of connection, long enough to support the home range of this bird (supplementation process). Colonisation of this recent landscape from the ‘bocage’, acting as a source of dispersers, required connectedness between hedgerows and planted dykes (source-sink process).

ENDICTYA HENDEYI SP. NOV., A NEW COASTAL DIATOM SPECIES FROM NORTH AMERICA

Endictya hendeyi E. Hemphill-Haley sp. nov. is described from Recent and Quaternary, estuarine and marine deposits along the west coast of the United States. This taxon is distinguished by its 1) consistently small valves; 2) areolae of uniform size on the valve face in linear tangential rows; 3) prominent, external spatulate extensions of the rimoportulae at the valve face/mantle junction; 4) externally projecting hyaline rim or flange at the interior edge of the mantle; and 5) discontinuous pattern of pores on the basal siliceous layer. The new species is compared to the generitype, E. oceanica Ehrenberg, as well as E. minor A. Schmidt and E. margaritifera A. Mann.

Excuse Me, You're Cramping My Style: Kinesthetics for the Classroom

If we accommodate our students' varying learning styles, Gage argues, our classes come alive. ere is your assignment: Draw a picture of what you consider to be the typical secondary English classroom. What does the room look like? What is the teacher doing? What are the students doing? Although I have no way of knowing what you've drawn, odds are that you've created a depiction of a conservative, structuralist learning environment. The desks are probably arranged in standard linear rows. The teacher is likely presenting the day's curricular objective via lecture and may or may not be making use of an overhead or writing the material on the board. And the students are presumably taking notes or listening attentively The above scenario, unfortunately, represents the ideal classroom environment to

Uterotrema australispinosa n. gen., n. sp. (Digenea: Spirorchidae), a Parasite of a Freshwater Turtle Emydura macquarii from Southern Queensland, Australia

Uterotrema australispinosa n. gen., n. sp. from the heart of the Murray River turtle Emydura macquarii (Pleurodira: Chelidae) is distinguished from other members of the Spirorchidae by the presence of a voluminous uterus; a single, lobed testis occupying the posterior quarter of the body; linear rows of 5-6 spines arranged along the lateral margins of the hindbody from the posterior rim of the acetabulum to the posterior end of the body; and the posterior end ventrally curved with a dorsal cluster of spines near the terminal end. This is the first report of a spirorchid from a member of the family Chelidae and from Australia.

Variants of cation arrangement in the 36 net of tantalates and niobates with 1:1 stoichiometry

We have analyzed and tabulated the variants of mutual ordered arrangements of cations of two types with 1∶1 stoichiometry in cation matrices having planar trigon 36 nets. A net with two nodes in its unit cell has a sole variant, which occurs in the wolframite type structure. With four nodes in the cell, there are two variants: the scheelite type and the variant found in α-and β-LaTaO4. With 6 nodes, there are six, and with 8 nodes, more than 20 variants. In the ABO4 (A=REE, B=Ta Nb) structural type (M'-fergusonite, fluorite, α-LaTaO4, β-LaTaO4, and fergusonite) having a more or less distorted face-centered cubic cation subcell in common, we have the wolframite type of arrangement for M'-fergusonite and fluorite, the scheelite type for fergusonite, and the partly scheelite type for α-and β-LaTaO4. We offer a system for representing the atomic arrangement by recording the alternation of atoms in linear rows of three directions.

Bed and Basin Tillage Practices for LEPA Irrigation

Bed and basin tillage practices are presented for wide bed cultivation under LEPA irrigation systems. Practices were selected to contain irrigation and rainfall water at the point of application for linear crop rows under a LEPA equipped center-pivot system. The grain sorghum crop was planted in two crop rows on top of 1.42 m (56 in.) wide beds. The average row spacing was 0.71 m (28 in.). Convex-topped beds and deep wide basins proved effective in confining the applied water to the area of application. A method of achieving the convex-topped beds was demonstrated during the 1992 crop season. The refinements in tillage practices helped overcome potential water application problems which can occur with LEPA irrigation techniques.

Structure of MoO 3 · 1/2H 2O by Conventional X-Ray Powder Diffraction

The crystal structure of the compound MoO 3 · 1/2H 2O was solved ab initio from conventional X-ray powder diffraction data and refined by the Rietveld method. This hydrate crystallizes in the monoclinic space group P2 1/ m with unit cell dimensions a = 9.6715(2) Å b = 3.701518(7) Å, c = 7.01975(1) Å, β = 102.403(1)°, and V = 248.40(1) Å 3, for Z = 4; 137 integrated intensities obtained by an iterative method were used to generate a Patterson map from which the initial positional parameters of two independent molybdenum atoms were derived. The remaining nonhydrogen atoms were located by Fourier methods. Refinement of the complete diffraction profile parameters (44 parameters, 575 reflections) converged to final agreement factors R p = 0.088, R wp = 0.113, and R F = 0.021. The structure consists of isolated layers parallel to (001), formed by double linear rows running along [010] and linked together through corner-sharing [MoO 6] and [MoO 5(H 2O)] octahedra. A double chain is built up from strongly distorted [MoO 6] octahedra sharing two common edges with each other, and the next one is in a similar layer, but with [MoO 5(H 2O)] octahedra. The successive layers are held together by hydrogen bonding to form a two-dimensional network.

The glossopterid group of plants in an evolutionary perspective

The glossopterid group of plants was the most dominant constituent of the Permian vegetation of the Gondwana Supercontinent. During last one hundred and fifty odd years, a staggering amount of data has accrued on leaves, wood, root, fructifications, seed and pollen that possibly belonged to this group. Evolutionary pathways with the group, however, are yet little understood.
 Considering the venation and epidermal features of the leaves, two patterns are unfolded; one with leaves having dichotomizing, almost parallel veins and stomata in linear rows, the other with dichotomising and anastomosing veins and stomata irregularly distributed in the mesh areas.
 Oldest glossopterid fructifications, viz., Arberia/Dolianitia show a certain resemblance with the cordaitalean fructifications, thus suggesting that group of plants with Cordaites/Noeggerathiopsis/Pantophyllum type leaf and Arberia/Dolianitia type infructescence probably was the precursor of the glossopterids. Overall evidence suggests the development of this group of plants along two successive lineages.

JUNCTIONAL PORES AND CELL WALL DEPRESSIONS OF HORMOSCILLA PRINGSHEIMII (CYANOPHYCEAE)1

ABSTRACTSassoon's isolate identified as Borzia trilocularis (but recently renamed Hormoscilla pringsheimii Anagnostidis and Komárek (1988) was studied with transmission electron microscopy because of its unusual combination of longitudinal wall features, described here in development for the first time. Junctional pores (linear rows of circumferential L‐II layer pores near crosswalls) developed into multiple, parallel series, unlike the pores in many other species, which form only single rows. In dividing cells, two single pore rows appear opposite crosswalls after crosswall initiation, but an additional parallel row is usually added to each row by completion of fission. Elongating cells reveal 3–6 parallel and uniformly spaced pore rows developing on each side of crosswall pairs; these rows may end up toward the center of the cell wall after cell elongation. Pores are 18–24 nm wide with a center‐to‐center and row‐to‐row distance of 24–36 nm and occur in an especially thick L‐II area. The second group of pit‐like pores of longitudinal cell walls are 50–135 nm‐wide depressions and have a center‐to‐center distance of 100–1000 nm. These depressions arise when the L‐II layer fails to form and appear next to a row‐pair of junctional pores soon after fission. Most depressions form single rows, but when they form several rows they may cover much of the surface of the cell. The L‐III and L‐IV wall layers line these L‐II layer cavities; the outer surface of the L‐IV layer around and within the depressions is covered with fibrous mucilage. Given their diversity, pores and depressions of longitudinal walls deserve further attention from functional and taxonomic points of view.

Diapiric spoke patterns

Not all finger-like diapirs evolve from or into linear walls as previously supposed. That would imply that all contemporaneous finger diapirs lie in rows and many do not. Physical models demonstrate that diapiric linear walls or rows of fingers have to be forced by lateral forces, lateral boundaries, or internal edge effects. By contrast, the kinematics of the simplest isothermal gravity overturns responsible for finger-like diapirs are geometrically, kinematically and dynamically similar to the “spoke patterns” of vigorous thermal convection. This is because Rayleigh-Taylor (RT) diapirism and Rayleigh-Bènard (RB) thermal convection are end members of a continuous dynamic spectrum due to any combination of compositional or thermally induced density inversions. All simple RT overturns are dynamically similar, but the vigour of thermal convection varies with the heat flow. The kinematics of spoke patterns are difficult to study in rapid, multiple overturns of thermal convection in low viscosity fluids. However, spoke patterns in slow, isothermal diapiric analogues can be analysed at any stage during their single overturn. Such studies indicate that two sets of spokes conduct fluids of different densities horizontally along the top and bottom boundaries to finger-like diapiric stems or plumes where they rise or sink to spread in polygonal bulbs at the opposite boundary. Spokes converge to hubs at the bottom boundary beneath stems feeding diapiric bulbs at the top boundary and vice versa. If the movement cells are considered centred on rising plumes, the cell corners are mapped by sinking plumes. The differences between spoke patterns and previously understood diapiric patterns are illustrated by geological examples with emphasis on relevance to the search for oil and gas. Physical arguments suggest that spoke patterns are probably the most common geometries of gravity-driven overturns in layered rocks of both the crust and the mantle.

Plot Size and Shape in Relation to Soybean Resistance for Velvetbean Caterpillar (Lepidoptera: Noctuidae)

During 1986, 1987, and 1988, selected plot sizes and shapes were evaluated for suitability in field experiments designed to compare soybean, Glycine max (L.) Merrill, cultivars for resistance to larvae of the velvetbean caterpillar, Anticarsia gemmatalis (Hübner). Plot size or shape did not significantly affect the relative rankings between cultivars in density or percentage of defoliation; therefore, any of the plot sizes or shapes examined in our experiments appear suitable for use in field experiments to compare soybean cultivars for resistance to this defoliating pest. Plot size and shape influenced the mean and precision of density and injury estimates. Estimates of larval density and percentage of defoliation were greater in plots of two or more rows than in one-row and hill plots. Precision of density and percentage of defoliation estimates were best for the plot size of two linear rows each 3 m long. Consequently, a plot size of two linear rows each 3 m long appears the best option for field screening experiments.

Freeze fracture analysis of cellulose terminal synthesizing complexes in Vaucheria

It is well known that cellulose is assembled by specialized enzyme complexes (known as terminal complexes = TCs) located on or within the plasma membrane.At least three types of TCs have been described: a single linear row of particles observed in the brown alga Pelvetia; linear multiple rows in Oocystis and in some green algae; and, hexagonally arranged particle “rosettes” in some algae and solitary rosettes in all land plants. A new linear type of TC has been found in a freshwater xanthophycean alga Vaucheria hamata. Fine structure of the TC has been analyzed by high resolution analytical techniques for freeze-replication. Further examination for its characteristics was carried out by the treatment with inhibitors for cellulose formation(2,6-dichlorobenzonitrile, DCB) and its crystallization (Tinopal LPW).v. hamata was cultured under appropriate light conditions and single cells were cut into small pieces and recultured for two days. They were plasmolyzed in 0.2M NaCl, washed with fresh medium, and then recultured with or without inhibitors for 4-10 h. The cells were placed on Balzers double replica supports and quickly frozen in liquid propane. The supports were inserted in a Balzers double replica holder cooled by liquid nitrogen and placed in the chamber of a Balzers BA 360. Cells were fractured at 2x10-4 Pa and etched for 1 min. Most of the specimens were rotary shadowed (1 rps) with Pt-C at an angle of 30° and coated with carbon. Replicas were cleaned with 50% sulfuric acid containing 5% sodium dichromate and distilled water, and observed at 80Kv on a Philips EM 420.

Neuromuscular junction development in the cutaneous pectoris muscle of Rana catesbeiana

Synaptic specializations were studied in the developing cutaneous pectoris muscle of Rana catesbeiana tadpoles and froglets to correlate nerve terminal morphology (by light and electron microscopy), accumulation of acetylcholine receptors, and the ability of the muscle to contract following nerve stimulation. This correlated approach was used to determine the developmental timing and possible causal relationship of events in nerve and muscle maturation at the neuromuscular junction. Initially, the cutaneous pectoris nerve trunk was present in the undifferentiated presumptive cutaneous pectoris mesenchyme, prior to muscle maturation. At stage XII when the muscle was first able to contract weakly in response to nerve stimulation, the motor nerve terminal endings were simple bulbous enlargements associated with diffuse subneural aggregations of acetylcholine receptors (indicated by diffuse speckles of rhodamine α-bungarotoxin fluorescence). Before stage XII no rhodamine α-bungarotoxin fluorescence was present anywhere in the muscle. The first stage in the organization of acetylcholine receptors at the neuromuscular junction was the accumulation of diffuse speckles of fluorescence beneath the terminal enlargements. This was followed by the clustering of receptors into small polygonal areas at each synaptic site, and finally the organization of receptors into parallel linear rows. Presumably this final stage was associated with formation of junctional folds. By stage XV the synapses were multiply innervated and had developed acetylcholinesterase activity. The general nerve terminal morphology and pattern of accumulation of acetylcholine receptors at cutaneous pectoris neuromuscular junctions were similar to those of the adult throughout metamorphic climax except that they still contained more than one motor axon. After metamorphic climax, elimination of multiple innervation occurred.

Observation on the successive development of surface structure in unhulled rice.

The surface of unhulled rice has a complicated structure. Therefore, simple observation of a matured hull from outside is not enough to clarify its structure. In order to obtain further information materials were collected over a long period of. development. The surface structure of these samples was then examined by scanning electron microscopy. In outer epidermis, elongation of macrohairs and differentiation of microhairs started 15 days before heading. The stoma-like cells were observed 1) in the lemma near the hooking portion with palea, 2) at the tips of both glumes and 3) in the awn. These cells were identified as stomata by their morphology and distribution. There were one or two linear rows of stomata in the lemma near the hooking portion, and in these rows few microhairs were observable. Examination of the inner epidermal layer showed many stomata around the veins co-existing with the microhairs. In the lateral veins (lemma) and central veins, the stomata and microhairs coexist in the same rows. Around the hooking portion, stomata and microhairs separately exist in different rows, and the former were located closer to the hooking portion. We have concluded that the stomata and hairs perform an important function in the water metabolism of the hull.

Fine Structures of Oocytes and Accessory Cells of the Ovary in the Starfish Patiria (Asterina) pectinifera at Different Stages of Oogenesis and After 1-Methyladenine-Induced Maturation: (starfish oogenesis/oocyte maturation/electron microscopy/cytoplasm).

Morphological changes in the growing and maturing oocytes of Patiria (Asterina) pectinifero were studied by electron microscopy. Oogenesis is of the solitary type. An extensive system of rough endoplasmic reticulum (ER) and Golgi complex (GC) develops in the ooplasm forming the cortical, yolk and secretory granules in its peripheral regions. The contents of the latter granules are released from the oocyte and form the vitelline membrane. At early stages of oogenesis, extensive multiplication of mitochondria results in formation of a large aggregate of these organelles in the perinuclear cytoplasm ("yolk nucleus"). After maturation of full grown oocytes has been induced by 1-methyladenine, the membranous cell structures are rapidly rearranged: vast aggregates of ER cisternae in the surface cytoplasm layer and single ER cisternae among yolk granules are disintegrated to small vesicles; the GC is reduced. These processes are suggested to be somehow related to changes in hydration of the cytoplasm and in rigidity of its surface layer. In maturing oocytes, the yolk granules form characteristic linear rows, trabeculae, traversing the cytoplasm and their boundary membranes fuse in zones of contact. Some granules are converted to multivesicular bodies, thus suggesting the activation of hydrolytic enzymes that form part of the yolk in echinoderms.

Dynamics of the reconstruction process Ir(100) 1 x 1-->1 x 5.

The structure transition Ir(100) 1\ifmmode\times\else\texttimes\fi{}1\ensuremath{\rightarrow}1\ifmmode\times\else\texttimes\fi{}5 is observed by means of low-energy electron diffraction. After the preparation of the metastable and bulklike 1\ifmmode\times\else\texttimes\fi{}1 surface structure the transition is started by thermal activation at T>800 K. Diffraction spot profiles as well as integrated intensities are measured as a function of time for different constant temperatures. It is shown that streaks appear between integral-order spots from which superstructure spots develop. Both spot widths and intensities change rapidly in the beginning of the transition but subsequently vary very slowly without approaching their equilibrium value. A real-space model is proposed according to which linear atomic rows of the first layer are shifted from their initial quadratic hollow positions into hexagonal-close-packed arrangement. The activation energy of the transition is determined from the intensity increase to be W=0.88\ifmmode\pm\else\textpm\fi{}0.03 eV.

Distribution of particle aggregates in the internodal axolemma and adaxonal schwann cell membrane of rodent peripheral nerve

Freeze-fracture studies on myelinated fibres from the internodal regions of rat and mouse sciatic nerve show symmetrical particle aggregates within the adaxonal Schwann cell plasmalemma and particle clusters in the axolemma. These are mainly confined to the vicinity of the internal mesaxon and the Schmidt-Lanterman incisures. The Schwann cell particle aggregates are concentrated as bands over the cytoplasmic pockets of Schmidt-Lanterman incisures and the paramesaxonal pockets. In the axolemma there are linear rows of particle aggregates along the groove related to the inner mesaxon and in bands to either side of it. The morphological features suggest the possibility of metabolic coupling between the axoplasm and the Schwann cell cytoplasm via the periaxonal space.

Synthesis and effects of basement membrane components in cultured rat Schwann cells.

Schwann cells, the myelin-forming cells of the peripheral nervous system, are surrounded by a basement membrane. Whether cultured rat Schwann cells synthesize the basement membrane-specific components, laminin and collagen type IV, and whether these components influence the adhesion, morphology, and growth of these cells have been investigated. Both laminin and collagen type IV were detected in the cytoplasm of Schwann cells by immunofluorescence. After ascorbate treatment, laminin and collagen type IV were both found in an extracellular fibrillar matrix bound to the Schwann cell surface. Laminin was further localized on the Schwann cell surface by electron microscopy using gold immunolabeling. Anti-laminin IgG-labeled gold particles were scattered over the cell surface, and linear rows of particles and small aggregates were found along the cell edges and at points of contact with other cells. When added to the culture medium, laminin acted as a potent adhesion factor, stimulating Schwann cell adhesion as much as eightfold above control levels on type IV collagen. In the presence of laminin, the cells became stellate and by 24 hr had extended long, thin processes. Laminin also stimulated cell growth in a dose-dependent manner and anti-laminin IgG completely inhibited cell attachment and growth in the absence of exogenous laminin. Thus, cultured Schwann cells synthesize laminin and collagen type IV, two major components of basement membrane, and laminin may trigger Schwann cell differentiation in vivo during early stages of axon-Schwann cell interaction before myelination.

Further studies on the junctional complex in the intestine of Sagitta setosa. Freeze-fracture of the pleated septate junction.

The intramembrane structures of the pleated septate junction which occur in the junctional complex of the intestine of the chaetognath Sagitta setosa have been investigated. The pleated septate junction is made up of linear rows of irregularly shaped and sized particles, often fused into short rods, and pits which can be fused into furrows. The distribution of these structures on E and P faces depends upon the preparative methods used. Many of the morphological characteristics are the same as those of the "lower invertebrate pleated septate junction type" defined by Green (1981 a). The physiological significance of this junction is obscure. On the basis of the presence of septate junctions (both of the paired septate junction and pleated septate junction types) which have mainly morphological characteristics of the "lower invertebrate pleated septate junction" we can add to the hypothesis that chaetognaths are not related to the molluscs and arthropods.

Small-angle X-ray scattering studies on the X-ray aggregation of malate synthase. Computer simulations and models.

Malate synthase undergoes an X-ray induced aggregation which can be monitored in situ by small-angle X-ray scattering; the analysis of scattering curves, taken at subsequent stages of aggregation, has led to the establishment of a tentative model for an aggregation in two dimensions (Zipper and Durchschlag (1980) Rad. and Environm. Biophys., in press). This model was checked by comparison of appropriate theoretical curves with the experimental curves. The theoretical scattering curves for this comparison were obtained by weighted averaging over the scattering curves calculated for various species of hypothetical aggregates. Based on the approximation of the unaggregated enzyme particle by an oblate cylinder, the aggregates were assumed to be composed of 2, 3, 4 or 6 of such cylinders, associated side-by-side in one and later on in two linear rows. THe weight fractions of the species were chosen so, that an optimum fit of the experimental mean radii of gyration and mean degrees of aggregation was achieved. The distance distribution functions calculated for the model are very similar to the functions derived from the scattering experiment. Cross-section Guinier plots of the scattering curves of the model reveal the occurrence of one and later on of two pseudo cross-section factors similar to those observed in the experimental scattering curves. The pseudo thickness factor of the model of the unaggregated particle is found to be retained in the model curves for all stages of aggregation. From these results it can be concluded that the model for the aggregation process is essentially consistent with the scattering behaviour of the aggregating enzyme. Small differences between the theoretical and experimental curves may be explained by the idealizations of the model. The comparison of theoretical curves for alternative models, assuming aggregation in three dimensions, suggests that these models are unlikely, though small amounts of three-dimensional aggregates cannot be ruled out completely.