Course Of Bending Research Articles

High resolution flow with glazing flow for optimized flow detection in transjugular intrahepatic portosystemic stent shunt (TIPS): First results.

Ultrasound follow-up of transjugular intrahepatic portosystemic shunt (TIPS) is challenging due to the bent course of the stent-graft. Aim of this retrospective study was to assess to which extent the combination of HR flow with Glazing Flow improves hemodynamic assessment in the ultrasound follow-up of TIPS. Comparative studies with CCDS and High Resolution (HR)-Flow with Glazing Flow were evaluated regarding image quality and artifacts on a 5-point scale (0 = cannot be assessed up to 5 = maximum image quality without artifacts). In all cases, an experienced examiner performed the examinations with a 1-6 MHz probe (Resona 7, Mindray). 61 ultrasound examinations in 48 patients were performed; the mean patient age was 54±14.2 years. The use of HR-Flow with Glazing Flow resulted in an improved flow display in 55/61 cases (90.2%). Both methods correlated well (r = 0.71), but HR flow with Glazing flow values were in general higher than CCDS values. The reading resulted in an average value of 2.52±0.54 for CCDS and 3.52±0.57 for HR flow with Glazing flow (p = 0.013). The combination of HR-Flow and Glazing Flow results in improved flow representation and reduction of artifacts in the ultrasound follow-up of TIPS.

Crack growth under three-point beam bending and fracture energy estimation for snow in relation to acoustic emission responses

The non-invasive monitoring of crack initiation and growth processes within snow, a poro-composite matrix, could be useful to predict the structural failure of a composite material. Present work is a new approach utilizing the non-invasive technique of acoustic emission (AE) to study the ongoing cracking and failures processes within snow beams which is difficult to visualize in real time. The progressive crack growth within the beams of snow followed by their failures is studied under three point beam bending in relation to AE. In this work, AE detection platform is developed and implemented for non-contact detection of acoustic emissions generated within a beam with the help of specialized needle-type AE waveguides in conjunction to wideband AE acquisition system. The AEs are detected for entire course of bending, crack nucleation, crack growth and rupture of the beams, both under static and dynamic load conditions. The crack initiation and growth in snow beams were generated without any predefined notch on its surface in a controlled and perceptible manner, particularly at low deformation rates (<0.2 mm/min). The ongoing crack growth, in terms of crack lengths and openings, were also studied from high resolution images, regularly collected during the experimental course. The prominent AE characteristics such as counts, amplitude, absolute energy, etc. were analyzed in context of bending, cracking and rupture of the snow beams for static as well as dynamic load conditions. The total strain energy, estimated in terms of the strain energy density, was imparted to the snow beam which contributed in the crack initiation and growth processes. Further, a fraction of the crack surface energy was manifested in the form of AE energy; therefore, a correlation was established between the crack surface energy and the liberated AE energy for static as well as dynamic loading of snow. The Griffiths model for global energy balance was applied to estimate the crack surface energy. The relation between crack surface energy and corresponding AE energy (released) could be very useful to estimate the fracture energy of the materials directly in terms of AE, non-invasively.

FLEXIBILITY BEHAVIOR OF CORONARY STENTS: THE ROLE OF LINKER INVESTIGATED WITH NUMERICAL SIMULATION

Flexibility is a vital property of stents and different stent structures lead to different flexibility behaviors. In this study, the finite element analysis was adopted and a virtual bending deformation was imposed to quantify the effects of linker pattern, linker number, bending direction and linker location on flexibility. Stent performance indicators, including stress distribution, deformation patterns and bending stiffness, were examined. Results indicate that higher levels of stresses are found on the linker struts, associated with much larger deformation. The linker number plays the most significant role in flexibility, and simply decreasing linker number could result in a sharp increase in flexibility and a decrease in stress. The linker pattern has great impact on stent flexibility, especially on the behavior of self-contact. Stents with different linker patterns could respond differently in the course of bending, and the stent with an offset peak-to-peak linker pattern is the best choice. It is also found that stent flexibility can be improved when fewer linkers lie in the compression area and the linker directions between two adjacent rows are consistent. The results obtained could provide useful information for the improvement of stent design and clinical choice.

Analysis of 3-dimensional finite element after reconstruction of impaired ankle deltoid ligament.

We compared four repair techniques for impaired ankle ligament deltoideum, namely Wiltberger, Deland, Kitaoka and Hintermann using a 3-dimensional finite element. We built an ankle ligament deltoideum model, including six pieces of bone structures, gristles and main ligaments around the ankle. After testing the model, we built an impaired ligament deltoideum model plus four reconstruction models. Subsequently, different levels of force on ankles with different flexion were imposed and ankle biomechanics were compared. In the course of bending, from plantar flexion 20° to back flexion 20°, the extortion of talus decreased while the eversion increased. Four reconstruction models failed to bring back the impaired ankle to normal, with an obvious increase of extortion and eversion. The Kitaoka technique was useful to reduce the extortion angle in a consequential manner. Compared with the other three techniques, the Kitaoka technique produced better results for extortion angle and the difference was statistically significant. However, in case of eversion, there was no significant difference among the four techniques (P>0.05). Lateral ligament's stress in all the four models was different from the normal one. When the ankle was imposed with extortion moment of force, stress of anterior talofibular ligament with the Kitaoka reconstruction method was close to that of the complete deltoid ligament. When ankle was imposed with eversion moment of force, stress of anterior talofibular ligament with Kitaoka and Deland reconstruction methods were close to that of the complete deltoid ligament. We concluded that Kitaoka and Deland tendon reconstruction technique could recover impaired ankle deltoid ligament and re-established its normal biomechanics characteristics.

Blood flow velocity in the arteries of the anterior cerebral artery complex in patients with an azygos anterior cerebral artery aneurysm: A transcranial color-coded sonography study

Objective It is presumed that increased blood flow through the single azygos anterior cerebral artery (Az) may contribute to the formation of an Az aneurysm. The aim of this study was to assess the blood flow velocities in the arteries of the anterior cerebral artery (ACA) complex in patients with the Az aneurysm. Patients and methods A series of three patients (2 men, aged: 65, 52 and 41) with an aneurysm (unruptured in two cases) of the distal Az was examined. Blood flow velocities in the Az and the A1 segment of the ACA were measured by means of a transcranial color-coded duplex sonography (TCCS) and the Az to A1 segment (Az/A1) velocity ratio was calculated. The control group consisted of 22 healthy subjects (mean age: 44 years). Results There was a trend toward decreased ( p = 0.06) mean blood flow velocity in the Az compared to the A2 segment of the ACA of the control group. Blood velocity in the A1 segment did not differ between the study and control groups. Pulsatility and resistance indices in the Az were similar to those in the A2 segment of the control group. There were no differences between the Az/A1 ratio in the study group and the A2/A1 velocity ratio in the control group. Conclusion Our results suggest that Az aneurysms are not associated with increased blood flow velocity in the Az. Possibly, a hemodynamic stress related to the Az bifurcation geometry, together with a bent course of this artery around the genu of the corpus callosum, predispose to aneurysm formation.

WAYFINDING BEHAVIOR AND SPATIAL COGNITION

The purpose of this research is to clarify the spatial cognition of the visually impaired in model courses. Experimental courses were a straight course without any obstructions, and 6 kinds of bent course. Subjects were 5 totally blind pedestrians, 5 eye-masked pedestrians, and 5 normal sighted pedestrians. The results are as follows. (1) In the case of the blind subjects, the wider the angle of the corner is, the lower the rate of the independent walk is. (2) The behavior of losing the way of the eye-masked is 2 times as much as that of the blind. The incidence of losing the way at the corner is 85 %. (3) In the correct answer for sketch map, the score of the blind is 90 points, while that of the eye-masked is 50 points. Even if the angle of the corner changes, the blind can draw the sketch map correctly. (4) At the destination, the difference of the direction angle of the blind is 19° and that of the eye-masked is 51°.

저탄소강판을 이용한 굽힘 가공에서 발생하는 꺾임 현상에 대한 발생기구 해석

In order to investigate the cause and condition of fluting in tangential bending of low carbon steel sheet, an analytic analysis, an experiment and a series of finite element analysis for bending process were done. The fluting in bended sheet was related with the yield point elongation of material. Due to the yield point elongation, unstable plastic hinge was occurred in course of bending of elastic perfectly plastic sheet. According to the analysis and computational results, lower yield point elongation than 5% was required to prevent fluting in 0.5-0.6t sheet in radius bending. The tendency of fluting occurrence was reduced as decreasing the radius of bending, increasing thickness of bended sheet, and removing irregularity in sheet and bending processes.

Measurement of the time course of bending of the back in the sagittal plane.

A simple, inexpensive method has been developed for measuring the position of the back, projected onto the sagittal plane, during flexion. Light-emitting diodes (LEDs) were attached to the skin overlying the T6, L1, L3 and L5 vertebrae. They started to flash, at a controlled frequency, at the beginning of movement from an upright to a flexed position. The positions of the markers together with the initial (upright) and final (flexed) positions of the back were recorded on a single photograph. A plumb line provided a vertical reference. Times were determined from the flashing frequency. Vertical and horizontal components of the position were measured from the photograph; their resultant represented total displacement at a given instant in time. The results were scaled so that the displacements were expressed as a fraction of their maximum value, and time was expressed as a fraction of the total movement time. The reproducibility of the technique was tested by making repeated measurements from a single healthy volunteer. At any instant, the horizontal, vertical and resultant displacements of the T6 marker could be determined to within 7% of their maximum values; the resultant displacement of the L5 marker could be determined to within 10%. The results from the other markers were less reliable.

Effect of calcium on dark adaptation in Phycomyces phototropism.

Adaptation processes enable phototropism of Phycomyces to operate over a 10-decade range of blue-light intensity (1 nW m-2-10 W m-2). To investigate the influence of calcium on dark adaptation, the phototropic latency method was employed with the modification that sporangiophores were temporarily immersed in solutions containing CaCl2 or LaCl3. Following such treatment, the time course of bending was found to have two components with distinct latencies and bending rates. After immersion in darkness for 30 min in LaCl3 solution or 1 h in a solution of CaCl2, MgCl2, or the calcium chelator EGTA, each sporangiophore was adapted to a blue light beam (1 W m-2) for 45 min by rotation around its vertical axis. Cessation of rotation defined the onset of the phototropic stimulus, at which time the intensity was reduced by as much as 10(3)-fold. For a 10(2)-fold reduction (to 10(-2) W m-2), immersion in CaCl2 (10-100 microM) reduces the latency 13 min for the early bending component and 18 min for the late component, whereas treatment with the calcium-channel blocker lanthanum (0.1-11 microM LaCl3) increases the latency 12 min for the early component and 13 min for the late component. EGTA (10 microM) also had an inhibitory effect, increasing the latency of the first and the second components by 7 and 10 min, respectively. In experiments performed similarly, but without the light adaptation treatment after immersion, no differences between calcium-treated and control sporangiophores were found. The bending rates of both components show only a weak dependence on calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

The accessory motor nuclei of the trigeminal, facial, and abducens nerves in the rat.

The cobalt labeling technique was applied to the trigeminal, facial, and abducens roots in order to investigate the location and morphology of motoneurons of the main and accessory motor nuclei of these cranial nerves in the rat. On the basis of soma-dendritic morphology, axonal trajectory, and tegmental location, three different accessory nuclei were distinguished in the brainstem. Neurons of the accessory nuclei of V and VII form a common club-shaped nucleus extending between the main motor nuclei of V and VII. The dendritic tree of these neurons is oriented in the dorsoventral direction and the axon invariably follows a dorsolaterally directed bent course. The accessory VI nucleus is located ventral and lateral to the main VI nucleus in the lateral tegmentum. The neurons have elongated perikarya, strong ventral and weak dorsal dendritic arbors, and the bent axonal course is directed dorsomedially. Neurons of the main VI nucleus have rounded perikarya and radial dendritic arborizations. Muscle groups innervated by the accessory and main motor nuclei have distinctly different functions.

THE MOVEMENT OF GROWTH REGULATORS IN PLANTS

SummaryBy sequential visual and photographic recording, the courses of the initiation of bending and the subsequent rates of curvature of the petiole and stem have been followed when a growth regulator is applied to (a) the leaf surface above the midrib of one primary leaf, (b) a partially excised short tongue of the midrib, and (c) the cotyledonary node at the junction of a cotyledon. In a comparison of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T) it was found that though the times taken to initiate bending are greatly dependent on the site of application, there are no significant differences between the two compounds. On the other hand, for indole‐3‐acetic acid (IAA), the initiation times are shorter and the equi‐effective doses are much smaller. Once bending has been initiated, for 2,4‐D and 2,4,5‐T the degree of curvature increases progressively, whereas for IAA the initial positive rate eventually becomes negative.Using 2,4‐D and 2,4,5‐T, labelled with carbon‐14 in the carboxyl group, autoradiographs demonstrated that entry into the vascular strands via the tongue of midrib take place in about 5 minutes, while for applications to the cotyledonary node radioactivity is present in the tip of the primary leaf within the same time.On the basis of these and other observations, it is concluded that under the controlled conditions selected, the initiation time for the bending of the stem following an application of either 2,4‐D or 2,4,5‐T to the leaf surface I cm from the tip can be broken down into (a) 79 minutes for enough of the auxin to pass from the leaf surface to the underlying vascular bundles, (b) 61 minutes to reach the first internode, and (c) 24 minutes to induce curvature. For IAA the corresponding figures for (b) and (c) are 31 and 17 minutes.The velocity of downward transport in the phloem is estimated at 10–12 cm/hour for 2,4‐D and 2,4,5‐T and 20–24 cm/hour for IAA. From differences in the initiation times for applications of 2,4‐D to the tip and base of the leaf the velocity was estimated to be 14–25 cm/hour.Simultaneously with observations on the course of bending, the amounts of [14C]2,4‐D and [14C]2,4,5‐T. present in the tissues were followed. When bending is initiated the petiole and first internode contain 0.0016 and 0.008 μg respectively.The distribution of 2,4‐D applied to one of the primary leaves was examined for periods up to 27 hours. Penetration into the leaf and subsequent export from the leaf are greatest when the application is made to the tongue of midrib, less for an application to the lower leaf surface and least for the upper surface. The pattern of accumulation is dependent on the amount exported. In general, accumulation is highest in the first internode and upper hypocotyl. At the end of 27 hours no 2,4‐D is yet present in the opposite leaf.

Phototropic Curvature in Phycomyces

The distribution of curvature and of bending speed along the cell's growing region are studied during steady state phototropic bending. At the start, elemental bending speed parallels the known axial distribution of growth rate. Hence regional phototropic sensitivity is initially determined by the local growth rate, and unilateral visible light acts proportionally at all levels of the growth zone. In the later course of bending, the bending speed distribution shifts downward instead of progressing upward in step with the cell's elongation. Furthermore, during phototropic inversion reversed bending begins high in the growth zone and progresses downward while normal bending continues below. These spatial and temporal changes in the distribution of differential growth are considered to be due to a fixed rate of supply of material used in growth that is transported from lower regions of the cell and asymmetrically distributed within the growth zone.