Application Of Tensile Force Research Articles

Strain Sensitivity of Carbon Nanotubes Modified Cellulose

Nanostructured cellulose was modified by different concentration and volume of dispersed multi-walled carbon nanotube (MWCNT) and double-walled carbon nanotube (DWCNT) solutions and its electrical properties were studied. The resulting flexible cellulose films have an electrical conductivity sensitive to changes in CNT concentration and immersion time in solution. The conductivity increases with increasing immersion time and volume and concentration of dispersed solutions; the conductivity for bacterial cellulose (BC) pellicles modified with DWCNT was increased from 0.034S cm-1 to 0.15S cm-1 and for BC pellicles modified with MWCNT it was increased from 0.12S cm-1 to 1.6S cm-1 when the immersion time was increased from 24h to 72h. These results are significantly higher than in previously reported work [1].The effect of strain on the resistance during application of tensile force is shown for a simple strain gauge employing cellulose with incorporated DWCNTs. The electrical resistance of the films displays a high sensitivity to strain. It seems that this sensitivity depends on the modifying conditions, where BC pellicles which are modified in a dispersed solution with a higher concentration of CNTs show larger changes in resistance with the changes in fractional extension

Monitoring of External Prestressing Tendons Construction Process of Jiamusi Highway Prestressed Concrete Bridge during Strengthening in China

Jiamusi highway prestressed concrete bridge is located in the Jiamusi City within Heilongjiang province in the east north of China. The strengthening and repairing of the bridge structure can be provided an effective and economic solution in appropriate situation. The objective of this study are to monitor the construction process of external prestressing tendons for strengthening of Jiamusi highway prestressed concrete bridge. Monitoring process includes measurement of external prestressing tendons natural frequency, monitoring of tensile forces values of external prestressing tendons, monitoring of development of anchor beams cracks, and monitoring of anchor beam deformation. The results of monitoring process show that the box girder No. 11 has the largest values of proportional coefficient (K) and the maximum value is 327.8. Box girder No. 8 has the largest values of frequency, the maximum value is 3.499. Five levels of tension are used in the application of tensile force in the tension process of external prestressing tendons. These levels are level 1=248.2kN, level 2=496.4kN, level 3=744.6kN, level 4=992.8kN, and level 5=1241kN. The measured tendons elongation values of left box girder No.8 are more than the theoretical values. For left and right box girder No. 9, side external tendons of left box No. 10, and left and right box girder No. 11, the measured values are less than theoretical values of elongation. After tension process, there are no new cracks in the top, web, and bottom of anchor beam and a small number of cracks developed slightly. These cracks are found around ducts of external tendons. The length of cracks rang from 0.03m to 0.5m and width rang from 0.05 mm and 0.25mm. The longitudinal deformation of the interface and top of anchor beam is very small, ranging from 0.001mm to0.115mm, which averaged 0.026mm. The overall state of anchor beams and box girders during strengthening is good.

Structural Basis for Mechanical Force Regulation of the Adhesin FimH via Finger Trap-like β Sheet Twisting

The Escherichia coli fimbrial adhesive protein, FimH, mediates shear-dependent binding to mannosylated surfaces via force-enhanced allosteric catch bonds, but the underlying structural mechanism was previously unknown. Here we present the crystal structure of FimH incorporated into the multiprotein fimbrial tip, where the anchoring (pilin) domain of FimH interacts with the mannose-binding (lectin) domain and causes a twist in the beta sandwich fold of the latter. This loosens the mannose-binding pocket on the opposite end of the lectin domain, resulting in an inactive low-affinity state of the adhesin. The autoinhibition effect of the pilin domain is removed by application of tensile force across the bond, which separates the domains and causes the lectin domain to untwist and clamp tightly around the ligand like a finger-trap toy. Thus, beta sandwich domains, which are common in multidomain proteins exposed to tensile force in vivo, can undergo drastic allosteric changes and be subjected to mechanical regulation.

Effect of eugenol-based endodontic sealer on the adhesion of intraradicular posts cemented after different periods

Objective:This study evaluated in vitro the influence of an eugenol-based sealer (EndoFill) on the retention of stainless steel prefabricated posts cemented with zinc phosphate and resin-based (Panavia F) cements after different periods of root canal obturation, using the pull-out test.Material and methods:Sixty upper canines were decoronated and the roots were embedded in resin blocks. The specimens were distributed into 3 groups, according to the period elapsed between canal obturation and post cementation: Group I - immediately; Group II - 72 h and Group III - 4 months. The groups were subdivided according to the type of cement used for post cementation: A - zinc phosphate and B - Panavia F. Following the experimental periods, specimens were subjected to pull- out test in an Instron machine with application of tensile force at a crosshead speed of 0.5 mm/min until post dislodgement. The maximum forces required for post removal were recorded (kN) and means were subjected to statistical analysis by 2-way ANOVA and Tukey-Kramer test (α=0.001)Results:There were statistically significant differences (p<0.01) between the posts cemented with zinc phosphate cement (0.2112 kN) and Panavia F (0.0501 kN). However, no statistically significant differences (p>0.05) were found between the three post cementation periods, regardless of the cement.Conclusions:It was concluded that the eugenol-based sealer influenced the tensile strength of the posts cemented with the resin cement, but had no influence on the time waited between root canal obturation and post space preparation/post cementation.

729 滑膜由来細胞が自己生成した3次元Scaffold-free組織のリモデリング(S08-2 細胞の構造とメカノバイオロジー(2),S08 細胞の構造とメカノバイオロジー)

Synovium cells obtained from the synovial membranes of porcine knee joints were cultured in DMEM in monolayer. After the cell density reached to 4.0×10^6 cells/dish, 2mM of ascorbic acid 2-phosphate was injected to promote the synthesis of extracellular matrix. Several days to one month after the injection, the synthesized matrix was manually detached from the substratum, and was then allowed active contraction for 1 hours to develop 3DSTs. A cyclic tensile force with the maximum force of 0.01N was applied to the 3DST for 1 hour a day in DMEM in an incubator. Tensile properties and micro structure of the 3DST were determined using a tensile tester and a differential interference contrast microscopy, respectively. Results revealed that the collagen fibers in the 3DST were closely aligned with the direction of tensile force application. The modulus of the 3DST became higher as compared with no-loaded control 3DST. These results suggest that 3DST changes its mechanical properties and structure in response to externally applied tensile force.

A Model of Experimental Spinal Cord Trauma Based on Computer-Controlled Intervertebral Distraction: Characterization of Graded Injury

: A new model of experimental spinal cord injury is detailed based on the application of tensile (distraction) force to the vertebral column of the rat. : To develop an experimental model of graded spinal cord injury by application of tensile forces to the vertebral column. : Distraction is frequently an integral component of human spinal cord injury, but the acute application of tensile forces to the spinal cord has not been modeled rigorously. : A computer-controlled, motorized outrigger device was used to apply a longitudinal stretching force to sublaminar hooks oriented proximally at T9 and distally at T11. Distraction force was applied using a program that varied the length, speed, and duration of its distraction. A modified 14-point Tarlov score was used to establish the presence of hindlimb dysfunction. This score was correlated with acute changes in somatosensory-evoked potential amplitude, the comprehensive open-field test of locomotor function at 4 weeks, and postmortem measurements of serotonin content and metabolism in spinal cord rostral and distal to the site of injury. : Of distraction parameters, only length of distraction correlated significantly with each outcome measure. For outcome measures, open-field test inventory and distal/proximal ratio of the spinal content of serotonin were correlated most closely with final Tarlov scores. Acute somatosensory-evoked potential amplitudes proved to be an excellent index of the acute injury but were poor measures of long-term outcome. : Distraction-induced spinal cord injury was uniformly mild in rats with intact facet capsular ligaments, regardless of distraction parameters. Cutting the facet joint ligaments consistently generated outcome measures associated with mild, moderate, and severe spinal cord injury at 3-, 5-, and 7-mm distraction lengths, respectively.

Tensile failure of C2 pedicles and of subsequent direct repair in a porcine model.

This repeated-measures biomechanical study evaluated the tensile force required to cause bipedicular (hangman's) fractures in isolated porcine C2 specimens, and the subsequent force to failure after direct fracture repair with bipedicular lag screws. To assess the pullout strength of direct lag screw fixation of hangman's fracture, relative to the strength of the intact specimens. Clinical studies have reported successful treatment of hangman's fractures by direct screw repair followed by a collar after surgery. However, to the authors' best knowledge, there has not yet been a biomechanical analysis of the force required for screw pullout after direct repair. Of 60 mounted porcine C2 specimens subjected to tensile anteroposterior force, hangman's fracture occurred in 15 cases, 12 of which were fixed with bipedicular 4.0-mm lag screws. These fixed specimens were retested to failure in the same manner. Most specimens had laminar fractures after the application of tensile force, with 15 of 60 (25%) showing bipedicular fractures. The force to bipedicular failure was 3259.1 +/- 148.5 N (mean +/- standard error of the mean). After screw fixation, the force to failure of the same specimens was 882.0 +/- 108.5 N (mean +/- standard error of the mean), or 27.3% of the intact bone. The pullout strength was substantial (882 N), although the relative strength of fixation was only 27.3% of the fracture strength shown by the intact specimens. The findings are discussed in relation to previous studies. To the authors' best knowledge, this is the first study to examine screw pullout forces after direct repair of hangman's fracture.

Quantitative evaluation of stress distribution in bulk polymer samples through the comparison of mechanical behaviors between giant single‐crystal and semicrystalline samples of poly(trans‐1,4‐diethyl muconate)

AbstractThe Raman shift and crystallite modulus were measured under the application of tensile force for a giant single crystal and a series of uniaxially oriented semicrystalline samples of poly(trans‐1,4‐diethyl muconate) (polyEMU). The apparent Raman shift factor αapp or a vibrational frequency shift per 1 GPa tensile stress was higher for the semicrystalline samples with lower crystallinity or lower bulk modulus. The apparent crystallite modulus E or Young's modulus along the chain axis in the crystalline region was not constant but varied remarkably between the giant single crystal and semicrystalline samples. A systematic change in αapp and E among the polyEMU samples with different preparation history could be interpreted quantitatively on the basis of a mechanical series parallel model consisting of crystalline and amorphous phases. The origin of different E and αapp was speculated to be a stress concentration on the taut‐tie chain contained as a parallel crystalline component in the mechanical model. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 444–453, 2003

Interaction of p38 and Sp1 in a Mechanical Force-induced, β1 Integrin-mediated Transcriptional Circuit That Regulates the Actin-binding Protein Filamin-A

Connective tissue cells in mechanically active environments survive applied physical forces by modifying actin cytoskeletal structures that stabilize cell membranes. In fibroblasts, tensile forces induce the expression of filamin-A, a mechanoprotective actin-binding protein, but the mechanisms and protein interactions by which force activates filamin-A transcription are not defined. We found that in fibroblasts, application of tensile forces through collagen-coated magnetite beads to cell surface beta(1) integrins induced filamin-A expression. This induction required actin filaments and selective activation of the p38 mitogen-activated protein kinase. Force promoted the redistribution of p38 to the integrin/bead locus and the nucleus as well as enhanced binding of the transcription factor Sp1 to proximal, regulatory domains of the filamin-A promoter. Force application increased association of Sp1 with p38 and phosphorylation of Sp1. Transcriptional activation of filamin-A in force-treated fibroblasts was subsequently mediated by Sp1-binding sites on the filamin-A promoter. These results provide evidence for a mechanically coupled transcriptional circuit that originates at the magnetite bead/integrin locus, activates p38, tethers p38 to actin filaments, promotes binding of p38 to Sp1 in the nucleus, and induces filamin-A expression.

Restriction of nyctinastic movements and application of tensile forces to leaves affects diurnal patterns of expansion growth.

Leaves of Ricinus communis L. show strong nyctinastic movements as well as diurnal variations of growth activity, combined with prominent basipetal gradients of relative growth rate. A novel technique, using digital image sequence processing, is able to resolve such spatio-temporal patterns of leaf growth with high resolution. In this paper we analyse the impact of prevention of nyctinastic movements, and the potential of tensile forces to overcome the retarding effects. Tensile forces affected leaf expansion and tissue expansibility in a dose-response relation. In a comparison with freely-growing leaves, an appropriate, optimal tensile force was identified that rebuilt the natural diurnal course of leaf expansion. With this tensile force, undisturbed patterns of temporal and spatial growth distribution as well as undisturbed concentrations of major cations, amino acids or soluble sugars were observed. However, diurnal fluctuations in starch content of almost fully-grown leaves were affected by the treatment and could not be compensated by tensile forces. This effect might point to a connection between diurnal growth variations of the leaf vein, biomechanical forces that synchronize growth within the vein, and metabolism of carbohydrates as growth substrates of the vein. We therefore hypothesize that interveinal tensions, which are produced during nyctinastic leaf movements, are (i) required for undisturbed leaf growth and (ii) can be simulated by application of adequate tensile forces.

Changes in the biomechanical properties of the rat interparietal suture incident to continuous tensile force application

This study was designed to investigate the relation between the biomechanical behaviour of rat interparietal sutures and expansion forces placed on them. Thirty-five 4-week-old rats were divided into four groups, a control group and three experimental groups subjected to mechanical expansion of the interparietal sutures with a tensile force for 15, 30 and 50 h. After expansion, the parietal bones, including the interparietal suture, were dissected as specimens for tensile tests. Under tension, the relaxed stress–strain plots in the control group could be better fitted by a power of 2.00, and the relaxed moduli were 0.64 and 4.51 MPa at the lower and the higher applied strains, respectively. An initial fall in the relaxed moduli at 15 h of expansion was followed by an increase over time. It is therefore suggested that the biomechanical behaviour of the interparietal sutures is influenced by the duration of an external force.

合成高分子の結晶構造解析における最近の進歩

Recent development in the techniques for the X-ray structural analysis of synthetic polymer crystals have been reviewed with some illustrations. In particular the usefulness of imaging plate system has been stressed and a new software for collecting quantitative data of the position and integrated intensity of the observed reflections has been introduced, which enabled us to apply the so-called direct method to the construction of the initial structural models necessary for the structural refinement. The structural changes of polymer crystals caused by an application of tensile force or by a temperature change have been discussed for two cases of polydiacetylene giant crystal and orthorhombic polyethylene.

Structural changes in ferroelectric phase transitions of vinylidene fluoride-tetrafluoroethylene copolymers: 1. Vinylidene fluoride content dependence of the transition behaviour

Structural changes occurring in the ferroelectric phase transitions of vinylidene fluoride-tetrafluoroethylene (VDF-TFE) copolymers with VDF contents of 81-0 mol% have been investigated by X-ray diffraction and i.r. and Raman spectroscopies. In a VDF 81%-TFE sample, the conformational change between the trans (low temperature) and gauche (high temperature) phases occurs in the temperature region close to the melting point with thermal hysteresis. The VDF 75%-TFE sample shows a similar transition between the low and high temperature phases but via the disordered cooled phase: the behaviour is close to that observed for vinylidene fluoride-trifluoroethylene (VDF-TrFE) copolymer with VDF 65 mol%. As the VDF content decreases, the transition becomes more diffuse: for the VDF 64%-TFE sample the trans-gauche conformational change occurs gradually over a wide temperature region with almost no detectable hysteresis. The X-ray fibre diagram taken at room temperature is of the cooled phase, which reversibly transfers into the low temperature phase by the application of tensile force. The same phenomenon is observed for VDF-TrFE copolymer with VDF 37%. In this way the transition behaviour of VDF-TFE copolymers with VDF contents of 60–80% corresponds to that of VDF-TrFE copolymers with lower VDF content. As the VDF content decreases, the low temperature phase is stabilized more due to the effect of the TFE monomeric units. The as-drawn VDF 41%-TFE sample shows an X-ray fibre pattern characteristic of the low temperature phase, which transforms irreversibly to the cooled phase by heating above 110°C. Tensile force causes the transition to the original low temperature phase irreversibly. VDF 23%-TFE sample exists in the stable ‘untilted’ all- trans chain conformation above room temperature. Below −40°C, the X-ray fibre diagram changes into an overlap of the patterns of the poly (vinylidene fluoride) planar zigzag structure and of the poly(tetrafluoroethylene) helical structure. The transitional behaviour has been discussed in comparison with that of VDF-TrFE copolymers and the factors governing these structural phase transitions have been investigated.

The morphologic and biochemical effects of tensile force application to the interparietal suture of the Sprague-Dawley rat

The purpose of this study was to correlate the histologic and biochemical responses of the interparietal suture to a range of tensile forces. Stainless steel spring implants, calibrated to generate expansive forces from 50 to 250 g, were placed across the interparietal suture in 85 female Sprague-Dawley rats. After experimental periods from 2 hours to 14 days, the interparietal sutures were evaluated by radiography, histology, and biochemistry. An in vivo/in vitro system was used for the biochemical analysis; total protein, proline incorporated, percent collagen, and alkaline phosphatase activity were measured. The radiographs and histology showed that in vivo suture expansion was achievable with 50 to 70 g of force, but the heavier forces showed greater sutural opening, more cellular proliferation, and more bone formation. This increased biologic response by the heavier forces was substantiated by an increase in sutural protein and alkaline phosphatase activity but not in percent collagen. It was concluded that changes in the total protein content of the suture were not primarily caused by proliferation of osteogenic cells and fibroblasts but due to an influx of transudate. In contrast, the increase in incorporation of 3H-proline and alkaline phosphatase activity correlated with the observance of bone formation. This study indicated a positive correlation between the magnitude of tensile forces and osteogenic response.

Rapid palatal expansion in cats: Effect of age on sutural cyclic nucleotides

Previous experiments indicate that bone cells respond to externally applied stimuli with fluctuations of cyclic nucleotide levels. The objective of this experiment was to study the response of bone at the midpalatal suture to the application of tensile forces in young and old animals, through an examination of the osteoblastic staining pattern for cAMP and cGMP. The midpalatal suture was rapidly expanded for 0, 10, and 15 days, respectively, in three young and three old cats. Fresh, frozen, unfixed, undecalcified maxillae were sectioned transversely and stained immunohistochemically for cAMP and cGMP. The staining intensity for both nucleotides was increased in the osteoblasts of the young treated animals, while in the old animals the osteoblasts were only faintly stained for cAMP and cGMP. These results demonstrate that bone cells of old animals are less responsive to tensile forces than the corresponding cells in young animals.

Immuno-histochemical localization of cyclic nucleotides in mineralized tissues: mechanically-stressed osteoblasts in vivo.

Previous experiments indicate that bone cells respond to external stimuli with fluctuations of cyclic nucleotide levels. The objective of this experiment was to study the response of alveolar bone to the application of tensile forces through an examination of the osteoblastic staining pattern for cAMP and cGMP. Cat canines were tipped by 80-g force for 0 to 48 hours. Fresh frozen, unfixed, undecalcified jaws were sectioned sagittally and stained immuno-histochemically for cAMP and cGMP. In tension sites, osteoblastic staining intensity for cAMP decreased gradually from one to three hours, and then increased by 24 hours. Intense staining for cGMP, visible in osteoblasts of all treated cats, peaked after three hours of treatment and then again at 24 hours. Generally, groups of cGMP-stained osteoblasts were found adjacent to unstained osteoblasts. The observed fluctuations in the osteoblasts staining pattern for cAMP and cGMP indicates involvement of these substances in the early response of osteoblasts to mechanical stimuli in vivo.