Root Attachments Research Articles

The role of bacterial motility in the survival and spread of Pseudomonas fluorescens in soil and in the attachment and colonisation of wheat roots

Motile and non-motile strains of Pseudomonas fluorescens SBW25 were constructed using different combinations of the lacZY, xylE and aph marker genes which allowed their detection and differentiation in soil, root and seed samples. The survival of motile and non-motile strains was investigated in both non-competitive and competitive assays in water and non-sterile soil. Although there was no difference between strains in water, the motile strain survived in significantly greater numbers than the non-motile strain after 21 days in soil. There was no significant difference between competitive assays, where motile and non-motile cells were co-inoculated into soil, and non-competitive assays where strains were inoculated separately. Bacterial survival decreased as matric potential increased from −224 to −17 kPa but matric potential had no significant effect on motile compared to non-motile strains. Vertical spread of both motile and non-motile strains was detected 6.4 mm from the inoculum zone after 14 days in the absence of percolating water. There was no significant difference, for either strain, in distance moved from the inoculum zone after 14, 26 or 40 days. The motile strain had a significant advantage in attachment to sterile wheat roots in both non-competitive and competitive studies. When the spatial colonisation of wheat root systems was assessed in non-sterile soil, there was no significant difference between the motile and non-motile strain from either seed or soil inoculum. However, when the whole root system was assessed as one sample unit, differences could be detected. Bacterial motility could contribute to survival in soil and the initial phase of colonisation, where attachment and movement onto the root surface are important.

341 蒸気タービンフォーク型翼植込部の低サイクル疲労寿命評価(GS-7 疲労(2))

A new evaluation method was developed for low-cycle fatigue life for fork-type root attachments of long steam turbine blades. In this study, low-cycle fatigue life was estimated by calculating the micro crack growth life under a steep strain distribution, using the micro-crack growth rate, which is proportional to the effective crack length according to non-linear fracture mechanics. To verify this evaluation method, low-cycle fatigue tests on pin joint models were conducted, in which the crack growth behavior at the inner surface of the pin hole was observed by interrupting the tests. The estimated results for micro-crack growth behavior agreed well with the measured results. To obtain the local strain range distribution for fork-type root attachments, a two-step FEM analysis was proposed, including three-dimensional analysis of a whole-blade model and two-dimensional elastic-plastic contact analysis of a single blade-fork model.

Anatomic and biomechanical analysis of the lower lumbar foraminal ligaments.

An anatomic cadaveric study to characterize the lumbar intraforaminal nerve root attachments. To characterize the intraforaminal nerve root attachments and describe their anatomic relationships and biomechanical properties. Observations during foraminotomies for lateral recess stenosis as well as lateral approaches for far lateral disc herniation have shown dense attachments between the nerve root and adjacent structures. Little or no information has appeared in the literature describing intraforaminal nerve root attachments. Twelve fresh-frozen human cadaveric lumbar spines were used to study intraforaminal ligamentous structures. Four cadavers were cut into sagittal sections for qualitative description, and eight were used for biomechanical testing. Histologic analyses were performed on samples of the foraminal attachments to assure that they were not vascular or neural structures. Biomechanical testing of the nerve roots with ligamentous attachments was performed measuring load to failure along the anatomic axis of the root. The dissections showed four distinct bands extending radially from the nerve root sleeve. The most prominent nerve root attachment was to the facet capsule posteriorly. Other ligaments fanned out with attachments inferiorly and superiorly to the adjacent pedicles and anteriorly to the intervertebral disc. Biomechanical study of the L3, L4, and L5 nerve roots showed a significant increase in strength at failure with axial traction, progressing from L3 to L5. The results demonstrate that these foraminal ligaments are normal anatomic structures within the intervertebral foramen of the lumbar spine. In addition, they may play a role in limiting motion along the nerve root.

Root :soil adhesion in the maize rhizosphere : the rheological approach

This study was designed to investigate the strength of attachment of plant seedling roots to the soil in which they were grown. The study also assessed the effects of differing soil textures and differing soil matric potentials upon the strength of the root:soil attachment. A device for growing roots upon a soil surface was designed, and was used to produce roots which were attached to the soil. In order to quantify root:soil adhesion, roots of maize seedlings, grown on the soil surface, were subsequently peeled off using a universal test machine, in conjunction with simultaneous time-lapse video observation. To clarify the partitioning of energy in the root:soil peeling test, separate mechanical tests on roots, and on two adherent remoulded topsoil balls were also carried out. The seedling root was characterised by a low bending stiffness. The energy stored in bending was negligible, compared to the root:soil adhesion energy. The mechanical properties of two adherent remoulded topsoil balls were a decrease of the soil:soil adhesion energy as the soil:soil plastic energy increased. These two parameters were therefore interdependent. Using a video-camera system, it was possible to separate the different processes occurring during the root:soil peeling test, in particular, the seed:soil adhesion and the root:soil soil adhesion. An interpretation of the complex and variable force:displacement curves was thus possible, enabling calculation of the root:soil interfacial rupture energy. At a given suction (10 kPa), the results of the peeling test showed a clear soil texture effect on the value of the root:soil interfacial rupture energy. In contrast, for the same silty topsoil, the effect of the soil water suction on the value of the interfacial rupture energy was very moderate. The root:soil interfacial rupture energy was controlled mainly by a product of microscopic soil specific surface area and the macroscopic contact surface area between the root and the soil. Biological and physical interactions contributing to root:soil adhesion such as root:soil interlocking mechanics were also analysed and discussed.

Symposium on glial interfaces in the nervous system: development and repair

This Anatomical Society symposium, held at University College, Cork in September 1995 was the first of its kind. The objective was to stimulate and facilitate constructive interaction between experts on topics relating to the various types of glial barrier which form partitions within the nervous system. Some of these barriers are transient and are found only during development, for example, those which define the limits of developing nuclei or fibre bundles. Others are permanent, such as those at the transitional zones which separate the CNS and PNS milieux at nerve root attachments to the neuraxis. Still others, such as glial scars, are seen only following injury when they tend to inhibit neurite regeneration. In experimental circumstances, for example following irradiation or chemical damage, glial barriers may be broken down and even relocated. This may be associated with Schwann cell invasion of the CNS and, experimentally, with Schwann cell and glial cell transplantation into demyelinated areas. Such transplantation studies are in turn related to remyelination and CNS axon regeneration and the factors which facilitate these. Twelve review lectures were given on these topics. Five articles based on these communications are reproduced here. The underlying theme was the relationship between advances in the understanding of fundamental nervous tissue biology, especially as related to glial cells, and potential developments aimed at treating CNS demyelinating diseases and achieving CNS regeneration.

Protective coatings in the gas turbine engine

The gas turbine provides one of the hardest environments challenging material systems today. Engine components are subject to rigorous mechanical loading conditions, high temperatures, and corrosive or erosive media. Historically, engine manufacturers have applied protective coatings to increase the durability and field performance of alloys or composites. Field experience as well as the development of processing technologies has led to the evolution of many new and improved coatings systems for a variety of engine component applications. In the fan and compressor areas, erosion-resistant coatings are used to minimize blade wear, antigallant coatings are used for fretting wear of blade root attachments and corrosion-resistant coatings are used for blade and disk materials. In the case of the combustor and turbine areas, diffusion and overlay coatings have been developed for oxidation and/or corrosion resistance and ceramic coatings are used widely as thermal barriers. In this paper, we shall review the current state of the art for coating technology in gas turbine engine applications with a look towards future needs and directions.

Factors affecting appressorium development in the vesicular–arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe

SUMMARYInvestigations on the luck of appressorium formation in the roots of the non‐host plant Lupinus albus L. showed that root exudates do not inhibit mycelial growth of the vesicular‐arbuscular mycorrhizal (VAM) fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, but that they hinder hyphal attachment and fungal recognition of roots. Exudates do not stimulate hyphal proliferation in the rhizosphere. G. mosseae hyphae were able to recognize and attach to excised root of both lupin and host plants, forming swellings resembling apressoria. No growth of G. mosseae hyphae was observed around simulated roots consisting of nylon, silk, polyamide and glass threads, whereas appressoria were formed on heterologous hyphae of VAM fungal species. The hypothesis that a purely thigmotropic stimulate could trigger hyphal attachment and the further differentiation of appressoria was excluded.

Biomechanics of the lumbar spinal nerve roots and the first sacral root within the intervertebral foramina.

This study consists of 3 sections: a descriptive study of the intervertebral foramen by dissection, supplemented by millimetric sections made with the cine-microabrasive apparatus (patented) on 12 specimens frozen with liquid nitrogen; a study of the attachments of the roots made during manipulations testing the resistance to avulsion of the rootlets, the roots, the dural sheath and the fibrous expansions at the periphery of the intervertebral foramen; and a study of the mobility of the roots in the foramina during movements effected within and outside the spine. We concluded that the classical description of an intervertebral foramen as occluded by a taut membrane like a drum-head is false as only perforated expansions attach the root to the foramen. Further, the points for attachment of the roots are the dura mater and the fibrous expansion passing from the foramen to the sheath of the spinal n. Finally, from the aspect of mobility, there are 2 distinct compartments and movements in one are not perceived in the other compartment if the attachments are unbroken. These attachments are a barrier interposed between the two compartments.

Ultrastructure of paired coniform 9 + 0 sensory cilia: a new type in the organ of Bellonci of the marine amphipod Gammarus setosus

The structure of modified 9 + 0 cilia in the organ of Bellonci was studied in Gammarus setosus from late embryonic development to adult after routine fixation, fixation with lanthanum treatment, and prefixation with ethylene diamine tetraacetic acid and sodium dodecyl sulphate. The cilia are distinct from known sensory cilia in that they occur in pairs and lack centrioles. The basal bodies are at right angles to each other. The basal body cylinders consist of dense microtubule doublets and have 3 regions: the basal cartwheel, the middle pinwheel and the distal transitional. The pinwheel, which has 9 fins of dense material attached to the doublets, is differentiated into a spiral attachment of the ciliary roots whose periodicity is 70 nm. The scanning electron microscope shows the roots as beaded, tapering ribbons. The coniform outer segments give rise to tubules, each with 1 or 2 single or double microtubules in its core. The tubules are in contact with extracellular chains of calcium granules inside the organ. A bend in the axoneme brings the paired outer segments together. Lamellar bodies develop from the ciliary tubules in embryos and juveniles, but not in adults, except after exposure to lanthanum.

An haustoria inducer for the root parasite Agalinis purpurea

Host recognition by the angiosperm root parasite Agalinis purpurea occurs through the development of haustoria, organs specialized for the attachment and penetration of host roots. Axenic cultures of Agalinis do not develop haustoria, but low molecular weight compounds produced by host plants induce haustoria development. Structure-activity studies have shown that highest levels of haustoria induction are afforded by flavonoids bearing specifically substituted methoxyphenol functionality. This paper examines Lespedeza sericea to determine the extent of this structure-activity relationship among hosts of Agalinis. A pentacyclic triterpene has been isolated from Lespedeza roots as a haustoria inducer, and extensive NMR and mass spectral experiments led to its characterization as soyasapogenol B (3β,22β,24-trihydroxy-olean-12-ene). The activity of soyasapogenol B is lower than the phenolic inducers, and modification of hydroxyl substitutents on soyasapogenol B abolishes activity. This haustoria inducer appears to be preferentially secreted from the roots of Lespedeza, but not in quantities sufficient to account for all haustoria inducing activity exhibited by the crude root exudate.

Secondary Development in the Cortex of Isoetes

True secondary development, which arises in the more or less mature cortex and not from the circumstelar, primary meristem, is described in three species of Isoetes. The secondary cortex develops in relation to the process of furrow formation and to the shedding of layers of dead cortex. In the furrows, the secondary cortex is aligned in files tangential to the axis of the corm; on the surfaces from which old cortex is shed, it is usually aligned in radial files. In I. japonica, however, the secondary cortex at the surface from which dead cortex has been shed may consist of randomly oriented pairs of cells, which result from the division of numerous primary cortical cells. In I. japonica, typically elongate furrow cells also may develop in the secondary cortex in no relation to the furrows between the lobes. In I. nuttallii, secondary cortex reminiscent of an abscission layer occasionally develops through the region of attachment of individual roots.

Investigation of the stress-strain state of turbine blade root attachments by the finite-element method

Investigation of the stress-strain state of turbine blade root attachments by the finite-element method

Progress on Ceramic Rotor Blade Development for Industrial Gas Turbines

This paper reviews progress made in the first year of a three-year program sponsored by EPRI to design and test ceramic root attachments, leading to the full development of ceramic rotor blades and cantilevered vanes intended for industrial gas turbines. Initial work has focused on a rotor blade attachment design. The specific rotor configuration chosen for development consists of a cooled low-alloy steel disk, a cooled intermediate super-alloy attachment piece, an uncooled ceramic blade, and the provision for a compliant interface at the ceramic/metal root attachment. A new root attachment design, in which the root and groove are curved in their transverse and longitudinal directions, is presented. Room temperature spin tests of dovetail root forms have provided encouraging results and indicate that continued development is warranted.

The Vascular Pattern of Italian Ryegrass (Lolium multiflorum Lam.) 4. The Peripheral Plexus, and Nodal Root Insertion

The interconnecting system of leaf traces constitutes only a fraction of the vascular tissue found in the base of a ryegrass stem. The tillers and nodal roots have their insertion in this congested region of the plant in addition to the majority of the leaf traces. Study of the attachment of nodal roots reveals the extensive differentiation of vascular tissue in a perforated cylinder surrounding the inner leaf trace system—the peripheral plexus. This plexus consists of two components, the diffuse bundles orientated along the stem axis, and interconnected with the root girdles orientated around the stem axis. The peripheral plexus which is bounded externally by a mestome sheath, makes numerous contacts with the leaf trace system within it, both directly and via the nodal plexi, and receives the vascular attachment of all the nodal roots. It appears in the stem at about the same time as adjacent nodal roots, and differentiates from meristematic tissue totally independently of the leaf trace system. The diffuse bundles themselves apparently differentiate acropetally in this meristematic tissue and are augmented by branches from leaf traces and the nodal plexi. The integrated vascular systems of leaf, stem, and root at the base of the grass plant, bounded by a mestome sheath, must allow total intercommunication between all organs. Nearly all tissue within the mestome sheath is vascular in nature and it is into this vascular tissue that the leaf traces associated with transfer cells are inserted.

The Vascular Pattern of Italian Ryegrass (Lolium multiflorum Lam.) 2. Development of the Seedling Axis to Maturity

The vascular system present in a grass seedling axis persists in a functional state at the base of a maturing plant, but undergoes a number of modifications. Two strands of phloem, accompanied by some internal xylem, differentiate in association with the bicollateral mesocotyl trace at right angles to the existing phloem, resulting in a tetrarch bundle. Lateral seminal roots are themselves tetrarch and the vascular insertion of a seminal root on to the mesocotyl is a distinctive three-dimensional feature. At the base of the mesocotyl the tetrarch bundle merges with the tetrarch bundle of the primary seminal root via a transition zone. The four phloem poles unite and then diverge again; the central xylem strand splits into three and then reunites, the two tissues being intimately interlocked by this rearrangement. The additional vascular tissue of the mesocotyl extends up into the coleoptilar node and becomes involved in the vascular attachment of nodal roots at this point. Additional vascular tissue continues to differentiate in the periphery of the maturing stem and is here termed the ‘peripheral plexus’. In the seedling, the xylem of the ‘bridge’ linking the mesocotyl trace with the scutellar trace is associated with xylem transfer cells and also contains tracheids with distinctive, thin-barred scalariform thickening. These transfer cells disappear as the plant matures but numerous tracheids with thin-barred scalariform thickening are then to be found. The possible significance of transfer cells in the coleoptilar node is discussed.

The fine structure of cellular layers and connective tissue space at spinal nerve root attachments in the rat.

AbstractTissue containing the attachment of nerve roots to the spinal cord was dissected from seven rats perfused with buffered aldehydes. Both dorsal and ventral roots were obtained from all cord levels. All tissues were prepared routinely for electron microscopy.The outer layers of the root sheath are homologous with the outer layers of the pia mater and are essentially continuous with it. The inner layers of the root sheath, which are a structurally modified and centrally directed continuation of the perineurium across the subarachnoid space, terminate as an open‐ended tube near the junction of the peripheral and central nervous systems. Here there is direct continuity between the endoneurial connective tissue space and the pial connective tissue space. The latter, in turn, communicates directly with the subarachnoid space through fenestrations between pial cells. The relationship of this to certain clinical manifestations is briefly discussed.

Mechanical Stability of a Two-Bladed Cantilever Helicopter Rotor

SUMMARY A theoretical analysis of the mechanical stability of a twobladed cantilever helicopter rotor, whose hub is mounted upon isotropic elastic supports in the horizontal plane and whose elastic blades employ fixed root attachments, has been made and is reported here. This case is a generalization of a problem treated by Feingold in reference 1 where the blades are assumed inelastic and attached to the hub by means of vertical hinges. It is found that Feingold's solution remains applicable also to the general case if the Coleman parameters Ai, A2, and A3 are appro­ priately defined by using the natural frequencies and modal shapes of the free uncoupled lag bending vibrations of the blades. The numerical determination of Coleman's parameters for a typical nonuniform two-bladed cantilever rotor are given in Appendix A. The effects of root tension straps are treated in Appendix B.

Investigations Into Blade-Root Fixings of High-Temperature Steels

Abstract The progress in mechanical engineering which has led in the past few years to much lighter designs of aircraft and land vehicles can be attributed to improvements in the materials used and to a much better adaptation of structural design to these materials. In cases where the temperature is low in aircraft and land conveyances, the engineer’s main problem has been alternating stresses. In applications where steels are used at high temperatures similar problems exist, but our knowledge is here less firmly founded than in the domain of alternating stress at room temperature. The test results described in the paper, however, point to a similar line of advance as has been followed in automobile and aircraft engineering. Here, too, it is important not only to develop better materials but also to improve designs if the strength properties of these materials are to be utilized fully. It has developed that an improvement in creep properties at high temperatures can only be attained, as a rule, at the price of an increase in embrittlement and sensitivity to notching. These considerations are particularly important in the attachment of blade roots to turbine disks. A large number of tests have been made with the aim of throwing some light on these problems and obtaining a clearer idea of the basic connection between structural design and strength.

Changes in length and position of the segments of the spinal cord with changes in posture in the monkey.

There are reasons for believing that the spinal cord, in spite of its sheltered position within the vertebral column, is subject to stresses that change with posture. The changes in posture may involve the trunk or the limbs. In the trunk, flexion must necessarily stretch the cord, since the vertebral canal increases in length. Of postural changes in the limbs, those that put traction on the nerves may be expected to stretch the cord. This is suggested by the observation of Inman and Saunders (1) that the trunks of the lower lumbar nerves, located in the intervertebral foramina, move distally when the hip is flexed and the knee is kept in extension. The present study was undertaken to measure the changes in length and position of the individual spinal cord segments (a) when the trunk is flexed and (b) when the extremities are moved into positions which put traction on the peripheral nerves. Material and Method Normal rhesus monkeys (Macaca mulatta) were killed by anesthetization and evisceration. The left leg and arm, and the left portion of the head were removed by sawing through the body in a sagittal plane close to the left side of the vertebral column. The saw passed in turn through the left hip joint, then close to the left side of the vertebral column, and in the same sagittal plane through the head. The postvertebral muscles were removed from the left side of the vertebral column; the right side of the back was left intact. The spinal cord was exposed by removing the vertebral laminae on the left side and incising the dura longitudinally. The spinous processes were left in place. The lateral aspect of the brain stem was exposed by removing the left margin of the foramen magnum, the left half of the cerebellum, and the left cerebral hemisphere. Pins 1/8 inch long, of fine iron wire, were inserted into the cord along the line of attachment of the dorsal roots, each pin being placed where the lowest rootlet of one nerve met the highest rootlet of the nerve just caudal to it. Because the dorsal rootlets of the first cervical nerve were either absent or rudimentary, the interval between the first and second cervical segments was marked by a pin at the level of the highest rootlet of the second cervical nerve. Three pins were placed in the brain stem in line with those in the cord, one at the level of the obex, the second at the junction of the medulla oblongata and pons, and the third at the junction of the pons and the midbrain. Similar pins were inserted at selected intervals in the large nerves of the lower limb, to lie lengthwise in the central long axis of the nerve. Nails inserted in the bodies of the vertebrae and in the bones of the lower limb served as reference points in locating pins placed in the central nervous system and in the nerves of the lower limb. The change in inclination of the nails in adjacent vertebrae was measured to obtain the range of movement at each of the intervertebral joints.

Two‐Spar Wing Stress Analysis

IT was now evident that some other effect would have to be taken into account to obtain a more exact agreement between theory and experiment, and it was fairly obvious that the non‐rigidity of the wing root attachments was the chief cause of the discrepancy. The method of dealing with this is given below, while the numerical results are plotted as curves C in Figs. 7 and 8. It will be seen from these curves that the modification to the theory, which is merely a modification to detail, has the desired effect.