Small Tension Research Articles

Bosentan inhibits cigarette smoke-induced endothelin receptor expression in pulmonary arteries

The endothelin (ET) system contributes to lung vascular tension and remodelling in smokers and chronic obstructive pulmonary disease (COPD) patients. This study examined the effect of cigarette smoke (CS) on ET receptor A (ET(A)) and B (ET(B)) expression in human pulmonary artery smooth muscle cells (HPASMCs) and human small intrapulmonary arteries, as well as their functional consequences. CS extract (CSE) increased ET(A) and ET(B) expression in HPASMCs and small intrapulmonary arteries, which was attenuated by bosentan, the ET(A) antagonist BQ123 and the ET(B) antagonist BQ788, and by blocking ET-1 with a monoclonal antibody against ET-1, suggesting a feed-forward mechanism mediated by ET-1 release. ET receptor (ETR) antagonism attenuated the CSE-induced HPASMC proliferation. Furthermore, CSE exposure increased the acute ET-1-induced small intrapulmonary artery contraction, which was attenuated by bosentan, BQ123 and BQ788. Pulmonary arteries from smokers and COPD patients showed a higher expression of ET(A) and ET(B) than those of nonsmoker patients. These results show a novel mechanism by which ETR blockade attenuates CS-induced ETR overexpression and, subsequently, small intrapulmonary artery tension. These data may be of potential value to explain therapeutic effects of bosentan in some forms of disproportionate pulmonary hypertension in COPD patients.

Surgical treatment of displaced medial clavicle fractures using a small T-shaped plate and tension band sutures

The surgical treatment of medial clavicle nonunion is associated with high complication and failure rates, particularly with regard to metal work migration. Therefore, we describe a simple surgical procedure for displaced medial clavicle fractures using a small T-shaped plate and multiple tension band sutures. After stabilizing the medial clavicle fracture using a small nonunion for the distal radius, our simple technique for preventing high complication and failure rates is performed easily and effectively, with sufficient tension band sutures.

Screening bulk curvature in the presence of large brane tension

We study a flat brane solution in an effective 5D action for cascading gravity and propose a mechanism to screen extrinsic curvature in the presence of a large tension on the brane. The screening mechanism leaves the bulk Riemann-flat, thus making it simpler to generalize large extra dimension dark energy models to higher codimensions. By studying an action with cubic interactions for the brane-bending scalar mode, we find that the perturbed action suffers from ghostlike instabilities for positive tension, whereas it can be made ghost-free for sufficiently small negative tension.

Electric charge on the brane?

We consider black holes localized on the brane in the Randall-Sundrum infinite braneworld model. These configurations are static and charged with respect to a spherically symmetric, electric Maxwell field living on the brane. We start by attempting to construct vacuum black holes, in which case our conclusions are in agreement with those of Yoshino [J. High Energy Phys. 01 (2009) 068]. Although approximate solutions appear to exist for sufficiently small brane tension, these are likely only numerical artifacts. The qualitative features of the configurations in the presence of a brane U(1) electric field are similar to those in the vacuum case. In particular, we find a systematic unnatural behavior of the metric functions in the asymptotic region in the vicinity of the anti--de Sitter horizon. Our results are most naturally interpreted as evidence for the nonexistence of static, nonextremal charged black holes on the brane. In contrast, extremal black holes are more likely to exist on the brane. We determine their near-horizon form by employing both analytical and numerical methods. For any bulk dimension $d>4$, we find good agreement between the properties of large extremal black holes and the predictions of general relativity, with calculable subleading corrections.

Study on Fracture Toughness of welded joints for heavy-thick steel plates by Centre-Notched small size specimen

A centre-notched small size tension test specimen was developed to evaluate the toughness against unstable brittle fracture from fatigue crack, which is initiated and propagated from the surface of the butt-welded joints Qof heavy-thick steel plates. Centre-notched small size tension test specimens were made from butt-welded joints of 70 mm heavy-thick steel plates and employed for the tests using this plate thickness as the specimen width. In this paper, the test results are evaluated and investigated.

Study on Fracture Toughness Evaluation by centre-notched small size specimen for heavy-thick steel plates

In order to evaluate the fracture toughness of steel plates, centre-notched wide plate tension test is usually conducted using 400 mm width specimens. However, a large testing machine and huge expenditures are necessary in the case of 50–90 mm heavy-thick steel plates. In this paper, centre-notched small size tension test is proposed to evaluate the fracture toughness of heavy-thick steel plates by a simplified method. That is, centre-notched small size tension test specimens using the steel plate thickness (70 mm) as the specimen — width were made and employed for the tests, and the test results were evaluated and investigated.

Aqueous biphasic microprinting approach to tissue engineering.

We summarize a recently developed microtechnology for printing biomaterials on biological surfaces. The technique is based on the use of immiscible aqueous solutions of two biopolymers and allows spatially defined placement of cells and biomolecules suspended in the denser aqueous phase on existing cell layers and extracellular matrix hydrogel surfaces maintained in the second phase. Printing takes place due to an extremely small interfacial tension and density difference between the two aqueous phases. The contact-free printing process ensures that both printed cells and the underlying cell monolayer maintain full viability and functionality. The technique accommodates both arbitrarily shaped patterns and microarrays of cells and bioreagents. The capability to print cells and small molecules on existing cell layers enables unique interrogations of the effects of cell-cell and cell-material interaction on cell fate and function. Furthermore, the very gentle conditions and the ability to directly pattern nongel embedded cells over cells make this technology appealing to tissue engineering applications where patterned multicellar organization with minimal scaffolding materials is needed, such as in dense tissues of the skeletal muscle and liver.

原子炉厚板冷却材配管溶接継手の3次元残留応力分布の固有ひずみ法による測定

The objective of this study is to ensure the safety of nuclear reactors. A number of accidents caused by leaks from welded zones at pipe penetration points of the reactor vessel or in coolant pipes have been reported at sites around the world. One of the main causes of such leaks is welding residual stress. It is therefore very important to know the welding residual stress in order to maintain the safety of the plants, estimate plant life cycle and design an effective maintenance plan. In this study, the inherent strain method combined with Finite Element Method (FEM) is applied to measure the welding residual stress accurately.A mock-up for a welded joint at a coolant pipe of an actual nuclear reactor was manufactured for the study. The inherent strain method is used to measure the three-dimensional residual stress distribution. In this method, the inherent strains are unknowns. When the residual stresses have a complex three-dimensional distribution, the number of unknowns becomes very large. The inherent strain distribution is therefore expressed with an appropriate function, significantly decreasing the number of unknowns.10 kinds of inherent strain distribution functions are applied to estimate the residual stress distribution of the joint. Applicability of each function is diagnosed. Accuracy and reliability of analyzed results are judged from three points of view, that is, residuals, unbiased estimate of variance of errors and necessary conditions from welding mechanics. Most suitable function is selected, which brings most reliable result.The characteristics of the three-dimensional residual stress distribution are cleared. The circumferential stress and axial stress are important, related to stress corrosion cracking (SCC). The circumferential stress is estimated to be large tension near the outer surface of welding finish region. The large tensile axial stress is produced near the outer surface, widely in the circumferential direction. Near the inner surface where SCC may occur, both stresses are small tension or compression.

Vesicles with multiple membrane domains

Vesicles with two types of intramembrane domains, both of which are in the fluid state, are studied theoretically using free energy minimization and Monte Carlo simulations. Specific examples are provided by liquid-ordered and liquid-disorderd domains, which are formed by phase separation within multi-component membranes. Multi-domain morphologies, which arise from the interplay between the bending energies of the domains and the line energy of the domain boundaries, are found for a wide range of these elastic parameters and can be further stabilized by the constraint of constant volume, by spontaneous curvatures, and/or by a difference in the Gaussian curvature moduli of the two types of domains. In the latter case, the vesicles attain stable multi-domain morphologies with up to six liquid-disordered domains. Morphologies with three and four such domains have also been observed experimentally, in qualitative agreement with our simulations. For sufficiently small line tension, “lipid rafts” with multiple liquid-ordered domains are also found to be stable if the liquid-ordered domains have a positive spontaneous curvature. The vesicles are found to undergo a variety of transitions between different multi-domain morphologies. Presumably the simplest way to explore these morphological transitions experimentally is by changing the vesicle volume via osmotic deflation.

Gibbs elasticity effect in foam shear flows: a non quasi-static 2D numerical simulation

The origin of the dissipation in liquid foams is not fully understood, especially in the large deformation, large velocity regime. Numerical simulations, now very accurate in the quasi static regime, are still sparse in the dissipative regime, and are all based on restrictive assumptions or very small bubble numbers. Here we present the results obtained with 2D numerical simulations involving 500 bubbles under simple shear, in a non-quasi static regime. The bubble description is kept as simple as possible and the dissipation is assumed to arise from surface tension variations induced by film area variations. This model leads to a steady state stress under simple shear that is well fitted by a Herschel–Bulkley law with an exponent 0.6. We show that small tension dynamical inhomogeneities induce foam structure modifications responsible for the largest part of the stress increase.

Stabilization of a blue phase by a guest component: An approach based on a Landau–de Gennes theory

We discuss, with the aid of numerical calculations based on a Landau-de Gennes theory, the stabilization of a blue phase in chiral liquid crystals by introducing a guest component. Our argument is based on a common speculation that cores of disclination lines with higher free-energy density are replaced by the guest component. We assume that the guest component forms sharp interfaces with the liquid crystal (strong segregation). We show that, by a suitable choice of materials with small interfacial tension, a guest component of volume fraction less than 10% drastically increases the temperature range of thermodynamic stability of a blue phase, in agreement with experiments [Kikuchi, Nature Mater. 1, 64 (2002)].

Radial stretching of a thin hollow membrane: biaxial tension, tension field and buckling domains

The radial stretching of a hollow thin membrane without compressive strength is considered within the framework of the small strain tension field theory. For each type of the uniform boundary conditions, the loading plane is partitioned into the domains of biaxial tension, tension field and buckling. The extent of these domains critically depends on the value of the Poisson’s coefficient and on the aspect ratio of the membrane. The stress and displacement fields are determined at an arbitrary stage of loading, when the outer biaxially stressed (taut) annulus surrounds the inner (tension field) portion of the membrane, characterized by continuously distributed infinitesimal wrinkles. The growth of the tension field as the loading increases is analyzed. It is shown that, depending on the Poisson’s coefficient and the aspect ratio of the membrane, the tension field may or may not spread throughout the whole membrane. For the fixed outer boundary, and the applied tension or a negative displacement at the inner boundary, and for a particular combination of the material and geometric parameters, the tension field instantly spreads to a specific depth within the membrane, dependent on the Poisson’s ratio and the outer radius of the membrane, remaining constant during further increase of the loading.

Nitrogen compounds in soil solutions of agricultural land

Plants are capable of taking up nitrogen (N) in both organic and inorganic forms, so the concentrations and relative proportions of different N forms in soils are likely to be important determinants of their N nutrition. Therefore, there is a need for greater knowledge of the N profiles of soils. In the study presented here we examined the potential plant-available N in soils from four sites with various agricultural histories (one recently fertilized), using small tension lysimeters to collect free and bound amino acids and inorganic N forms in solution, with minimal soil disturbance and with intact plants present. Subsequent analysis showed that concentrations of free amino acids ranged from 0.1 to 12.7 μM, whereas concentrations of bound amino acids were on average 50 times higher, and higher than ammonium and nitrate concentrations in all three unfertilized soils. In contrast, nitrate strongly dominated in the fertilized soil. Bound amino acids are likely to represent a potential replenishment pool for free amino acids, so the abundance and rate at which amino acid-containing substances are depolymerized might be important determinants of the availability of free amino acids. Our results highlight the need for further research on the liberation of free amino acids from polymers in agricultural soil, and the importance of bound amino acids as N sources for plants. ► Nitrogen compounds were analyzed in soil solution collected from the root zone in undisturbed soil. ► Bound amino acids concentrations were higher than inorganic nitrogen in soils solution of all unfertilized soils. ► Nitrate strongly dominated in soil solution from fertilized soil.

Evaporation Method for Measuring Unsaturated Hydraulic Properties of Soils: Extending the Measurement Range

The evaporation method is frequently used for simultaneous determination of soil water retention and hydraulic conductivity relationships. Tension is measured at two depths within a short soil column as water evaporates from its surface. Water content and flux are determined by weighing the column. Tensions, water contents, and fluxes are used to derive the water retention curve and the unsaturated hydraulic conductivity function. The measurement range of the conventional procedure is limited on the wet end by the inability of pressure transducers to accurately register very small tension differences. Hence, the resulting calculated hydraulic gradient in the vertical direction is associated with large uncertainties. On the dry end, water cavitation in the tensiometer, which typically occurs around 70 to 90 kPa, is the limitation. We present here a new design based on improved tensiometers that resist cavitation to much higher tensions, some reaching values as high as 435 kPa. On the wet end, data from a simple steady‐state method were used to supplement the evaporation method. On the dry end, applying the new tensiometers enabled the quantification of hydraulic functions up to 293 kPa average tension. Experimental results and soil water simulation affirmed the validity of the linearization assumption, even on the dry end when nonlinear tension–depth profiles emerge. The application of evaporation functions as a supplement for frequent weighing reduces costs for the equipment and increases the effectiveness of the method. Their validity for deriving fluxes was confirmed for the extended range, too. Results are presented for soil samples of different textures (sand, loam, silt, clay, and peat), various origins, and various dry bulk densities.

Photoelastic Stress Analysis Surrounding Implant-Supported Prosthesis and Alveolar Ridge on Mandibular Overdentures

The purpose of this research was to evaluate the maximum stress around osseointegrated implants and alveolar ridge, in a mandible with left partial resection through a photoelastic mandibular model. The first group consisted of two implants: traditional model (T), implants placed in the position of both canines; fulcrum model (F), implants placed in the position of left canine CL and right lateral incisor LiR. Both models linked through a bar and clips. The second group was consisted of three implants, with implants placed in the position of both canines (CR and CL) and the right lateral incisor (LiR), which composed four groups: (1) model with 3 “O” rings, (2) model 2 ERAs, bar with clips, (3) model 2 ERAs bar without clips; (4) model “O” ring bar and ERA. An axial and an oblique load of 6.8 kgf was applied on a overdenture at the 1st Pm, 2nd Pm, and 1st M. Results showed that the area around the left canine (CL) was practically free of stress; the left lateral incisor (LiL) developed only small tensions, and low stress in all the other cases; the right canine tooth suffered the largest concentrations of stress, mainly with the ERA retention mechanism.

Tensile and compressive microspecimen testing of bulk nanoporous gold

Nanoporous gold (np-Au) is a macroscopically brittle material, which poses difficulties for tensile testing of bulk specimens. By combining a fabrication approach that minimizes cracking in bulk np-Au and a microspecimen test technique that permits small testing volumes, both tension and compression tests were performed on sub-millimeter gage thicknesses of np-Au. Compressive strength was higher than tensile strength, as would be expected for a brittle material, but all strength values were significantly lower than literature values for nanoindentation testing. Measured elastic modulus was nearly the same in tension and compression, and was much lower than Gibson-Ash-by scaling relations would predict for porous gold with this density.

Flat 3-brane with Tension in Cascading Gravity

In the cascading gravity brane-world scenario, our 3-brane lies within a succession of lower-codimension branes, each with their own induced gravity term, embedded into each other in a higher-dimensional space-time. In the (6+1)-dimensional version of this scenario, we show that a 3-brane with tension remains flat, at least for sufficiently small tension that the weak-field approximation is valid. The bulk solution is singular nowhere and remains in the perturbative regime everywhere.

Biomechanical models for clinical data analysis of pressure‐volume relationship in the human eye

Abstract Purpose To develop mechanical models describing the pressure‐volume relationship for the human eye and to compare the results obtained with clinical data in order to find out which mechanical characteristics affect this relationship most significantly. Methods The fibrous coat is treated as a connected elastic shell consisting of two spherical segments with different radii and mechanical characteristics. The dependence of the intraocular pressure on the volume is analyzed using three different models in which the sclera and the cornea are modeled (1) by soft shells; (2) by transversally isotropic shells with small tension modules in the transverse direction; and (3) by 3D elastic solids. The models are studied analytically and numerically, the latter using FEM ANSYS software. Results The results are obtained over a wide range of parameters using all three models. Conclusion The models proposed predict a generally nonlinear relationship between the intraocular pressure and volume. The parameters of both the sclera and the cornea affect this relationship, the role of the sclera being more important. In the first approximation the simple soft shell model is in good agreement with the clinical data.

A comparative study of contractility of the heart ventricle in some ectothermic vertebrates

The purpose of this study was to analyze contractility of the heart ventricle in selected reptilian and amphibian species having the same ventricular excitation pattern. Systolic time intervals and indices of contractility of the heart ventricle were measured in anaesthetized frogs, snakes, and tortoises by use of polycardiography. The electromechanical delay was significantly shorter in tortoises compared with the other two species. The isovolumetric contraction time in frogs was approximately twofold longer than in reptiles. The pre-ejection period was the longest in frogs and the shortest in tortoises, whereas snakes were intermediate. The ejection time was slightly longer in tortoises compared with the other two species. The greatest isovolumetric contraction index and the smallest myocardial tension index corresponded to the frog and tortoise heart ventricle, respectively. The intrasystolic index in tortoises was significantly greater than in frogs, whereas quite similar to that in snakes. The frog ventricle had lower contractility compared with the reptilian one. Although ventricular contractility tended to be lower in snakes compared with tortoises, this difference was not statistically significant. Possible causes for these differences are discussed. We suppose a large variety in ventricular contractility among amphibian and reptilian species having the same ventricular activation pattern. This variety may be conditioned by heart anatomy, intracardiac shunting, lifestyles, and habitats. It can only be hypothesized that on the average, ventricular contractility is higher in reptiles compared with amphibians and in chelonians compared with snakes.

Liquid plug propagation in flexible microchannels: A small airway model.

In the present study, we investigate the effect of wall flexibility on the plug propagation and the resulting wall stresses in small airway models with experimental measurements and numerical simulations. Experimentally, a flexible microchannel was fabricated to mimic the flexible small airways using soft lithography. Liquid plugs were generated and propagated through the microchannels. The local wall deformation is observed instantaneously during plug propagation with the maximum increasing with plug speed. The pressure drop across the plug is measured and observed to increase with plug speed, and is slightly smaller in a flexible channel compared to that in a rigid channel. A computational model is then presented to model the steady plug propagation through a flexible channel corresponding to the middle plane in the experimental device. The results show qualitative agreements with experiments on wall shapes and pressure drops and the discrepancies bring up interesting questions on current field of modeling. The flexible wall deforms inward near the plug core region, the deformation and pressure drop across the plug increase with the plug speed. The wall deformation and resulting stresses vary with different longitudinal tensions, i.e., for large wall longitudinal tension, the wall deforms slightly, which causes decreased fluid stress and stress gradients on the flexible wall comparing to that on rigid walls; however, the wall stress gradients are found to be much larger on highly deformable walls with small longitudinal tensions. Therefore, in diseases such as emphysema, with more deformable airways, there is a high possibility of induced injuries on lining cells along the airways because of larger wall stresses and stress gradients.