Tension Capacity Research Articles

Theory and observation of spontaneous oscillatory contractions in skeletal myofibrils.

At low levels of activation, an isometrically-held myofibrillar preparation on the descending limb may exhibit persistent oscillations of period 1-6 s in tension and sarcomere lengths. We propose a sarcomeric theory of spontaneous oscillatory contraction, based on the phenomena of force creep and delayed length activation. The time delay leads to oscillations and controls their period. A computer model using these ideas simulates spontaneous oscillatory contraction for fixed-end fibres only if isometric tension capacity varies slightly along the fibre. The form of this inhomogeneity controls a diversity of spontaneous oscillatory contraction behaviour: the tension waveform can vary from large and sinusoidal to small-amplitude pulses or chaotic behaviour, and these variations are observed in slow-twitch soleus fibres from the same animal (rat). The model predicts that oscillatory and quiescent regions coexist in the fibre, with large-amplitude sawtooth waveforms in sarcomere length in the former as observed. It can also generate travelling-wave structures, similar to those found by the Tokyo group, in oscillating regions when there is a spatial gradient in isometric tension capacity. Phase discontinuities in sarcomere length occur near the oscillatory-quiescent boundary. Predictions for the Ca2+ concentrations and sarcomere lengths in which spontaneous oscillatory contraction occurs and for differences in the spontaneous oscillatory contraction frequencies of fast- and slow-twitch fibres compare well with experiment. Spontaneous oscillatory contraction is also predicted under isotonic conditions.

Development and Experimental Investigation of a Space Frame Connector

A recently developed space frame connector, and the experimental investigation carried out to evaluate its strength and failure mechanisms are presented in this paper. Four sizes of connectors, namely 48 mm, 60 mm, 76 mm and 89 mm joints, are tested to failure. The characteristic and failure behaviour of each connector under the principal actions for axial tension and compression as well as the secondary effect of bending at the joint are observed and reported. Joint and member capacities are also assessed analytically. Useful structural parameters such as rotational stiffnesses of the joints, buckling capacities of members as well as tension and bending capacities are evaluated and compiled for easy reference. Comparison of experimental results and predicted values show reasonably good agreement.

Behavior of Arc Spot Weld Connections in Tension

Arc spot welds, commonly called puddle welds, are widely used for connecting cold‐formed steel roof decks to their supporting members. These support members are typically hot‐rolled steel beams or girders, or the top chord of open‐web steel joists. A comprehensive experimental study of the tension strength of arc spot weld connections used to affix a cold‐formed steel roof deck to its support member was conducted. The study investigated the key parameters that influence the connection strength: steel thickness, tensile strength, and ductility; type of weld process, automatic or manual; cross section of the roof deck; loading condition, symmetrical or eccentric load; and geometry of connection. Based on the experimental results obtained from over 260 connection tests, equations have been developed that predict the tension capacity of an arc spot weld connection. These equations are easily applied, and lend themselves to use by structural designers.

Physical and thermal properties of the water-lithium bromide-lithium nitrate system

The physical properties (density, viscosity, surface tension, solubility and vapour pressure) and thermal properties (heat capacity and heat of mixing) of the water-lithium bromide-lithium nitrate system (4:1 LiBr:LiNO 3 by mole) were measured. The measurements of density, viscosity, surface tension, vapour pressure and heat capacity were carried out at various temperatures and absorbent concentrations. The solubility data were obtained in the temperature range 283.55–416.65 K. The heats of mixing at 298.15 K were obtained for solutions with absorbent concentrations from 0 to 61.5 wt%. Empirical formulae for the density, viscosity, surface tension, solubility and heat capacity of this system were obtained from experimental data. The vapour pressure data were correlated as an Antoine-type equation. The integral heat of mixing data were correlated as a Redlich-Kister-type equation. Enthalpy-concentration charts for the liquid and vapour phases of this system were constructed on the basis of the data obtained.

The effect of bolt stagger for block shear tension failures in angles

For various reasons, structural tension members may not always transmit load to their end connections through all of their cross-sectional elements. The resulting shear lag reduces the ultimate strength of these tension members. When connections are relatively short and have shear lag effects, block shear will usually be the mode of failure. This paper investigates, using finite element analysis, the effect that the stagger of bolt patterns has on ultimate block shear capacity. Significant differences from current code practices are found. In particular, it is found that stagger may not always increase the tension capacity as codes currently indicate.

Successful extended hypothermic cardiopulmonary preservation for heart-lung transplantation

The inability to obtain sufficiently extended hypothermic organ preservation is a major restriction on clinical heart-lung transplantation. We used core cooling, nonrecirculating retrograde heart perfusion, and lung immersion with liposomal recombinant human superoxide dismutase in an attempt to provide effective 12-hour cardiopulmonary preservation. Donor dogs supported by cardiopulmonary bypass were rapidly cooled to 15 degrees C with cardioplegic arrest, and heterotopic heart and unilateral left lung transplantations were performed. In control dogs (n = 7), hearts and lungs, harvested after core cooling and cardioplegic arrest, were transplanted with a total mean ischemic time of 88 +/- 5 minutes. In group II (n = 7), heart-lung blocks were similarly excised but preserved at 4 degrees C for 12 hours (756 +/- 30 minutes) and then transplanted. During preservation, the lungs were immersed in hyperosmolar extracellular solution. For the heart, retrograde coronary sinus perfusion was performed with intracellular solution containing perfluorochemicals at a temperature of 4 degrees C and a rate of 30 ml/hr for 12 hours. In group III (n = 7), donor organs were similarly excised and preserved for 12 hours (726 +/- 39 minutes), except that liposomal recombinant human superoxide dismutase was administered during harvest, preservation, and reperfusion. Myocardial function, assessed by the ratio of end-systolic pressure to end-systolic dimension, after the 12-hour preservation period in both experimental groups was similar to that of the control group 4 and 6 hours after transplantation. The mean arterial oxygen capacity of the transplanted left lung during ventilation with an inspired oxygen concentration of 40% was also similar in each group. In contrast, the 12-hour preservation of pulmonary function assessed by pulmonary vascular resistance, the accumulation of extravascular lung water, and histologic evidence of alveolar wall injury, interstitial edema, and perivascular hemorrhage were significantly impaired in the absence of liposal recombinant human superoxide dismutase. These findings suggest that successful extended cardiopulmonary preservation for heart-lung transplantation is possible with core cooling, nonrecirculating retrograde heart perfusion, and hypothermic lung immersion incorporating liposomal recombinant human superoxide dismutase.

Adsorption of α-, ⨿- and γ-cyclodextrins on mercury electrodes from 1 M NaC1O 4 and 0.5 M Na 2SO 4 aqueous solutions

The adsorption of α-, ⨿- and γ-cyclodextrins on mercury electrodes from l M NaClO 4 and 0.5 M Na 2SO 4 was investigated, using surface tension and differential capacity measurements. All three cyclodextrins adsorb on mercury and, in addition, α- and γ-cyclodextrins exhibit a behaviour typical of the two-dimensional condensation of organic adsorbates in both electrolytes. They also show strong reorientation effects in the adsorbed state. A comparison of possible models of electrode occupation by surfactant molecules with the experimentally determined surface excesses shows that at less negative potentials the molecules of cyclodextrins are oriented with the cavity perpendicular to the electrode surface, while at more negative potentials an orientation intermediate between the “parallel” and “perpendicular” prevails.

Effect of aggregates in bulk and surface properties: surface tension, foam stability, and heat capacities for 2-butoxyethanol + water

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of aggregates in bulk and surface properties: surface tension, foam stability, and heat capacities for 2-butoxyethanol + waterFrancisco Elizalde, Jesus Gracia, and Miguel CostasCite this: J. Phys. Chem. 1988, 92, 12, 3565–3568Publication Date (Print):June 1, 1988Publication History Published online1 May 2002Published inissue 1 June 1988https://doi.org/10.1021/j100323a048RIGHTS & PERMISSIONSArticle Views375Altmetric-Citations42LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (529 KB) Get e-Alerts

Effects of prolonged epinephrine infusion on blood respiratory and acid-base states in the rainbow trout: Alpha and beta effects

Rainbow trout were infused continuously for 12h with epinephrine in the presence or absence of alpha-and/or beta-adrenergic blockade to characterize the specific adrenergic mechanisms involved in the control of blood acid-base status and oxygen transport capacity. Infusion of epinephrine, alone, produced a transient respiratory acidosis, as indicated by an increase in carbon dioxide tension and a decrease in whole blood pH, yet arterial oxygen tension was elevated. Red blood cell pH increased by approximately 0.2 pH units during epinephrine infusion and this increase as well as the increase in oxygen tension were prevented by pretreatment with propranolol (a beta-adrenergic antagonist). Epinephrine infusion during alpha-adrenergic blockade caused a prolonged elevation of blood carbon dioxide tension and abolished the increases in hematocrit and hemoglobin concentrations observed during epinephrine infusion alone. Infusion of the alpha-adrenergic agonists phenylephrine (an alpha1 agonist) or clonidine (an alpha2 agonist) caused respiratory acidosis (decreased pH, increased CO2 tension) and a reduction in oxygen tension. Infusion of isoprenaline (a non-specific beta agonist) caused delayed increases in carbon dioxide and oxygen tensions. We speculate that the increased carbon dioxide tension observed during epinephrine infusion is a result of beta-adrenoceptor mediated inhibition of red blood cell bicarbonate dehydration and not branchial convective or diffusive adjustments. The effects of epinephrine on blood O2 tension, content and carrying capacity are discussed with reference to the participation of alpha- and beta-adrenergic mechanisms at the gill, spleen and red blood cell.

Tension Capacities of Running Skyline Yarders

ABSTRACT LOGGING planners have used 'safe' working tensions, usually one-third of breaking strength, when estimating payloads. Yarders have not always been able to handle the loads predicted on this basis. This study examined, via theoretical modeling of the drive trains, the capabilities of fifteen yarders which could be rigged as running skylines. We found that, in many cases, lines could not be tensioned to one-third of breaking strength due to clutch, brake or interlock limitations. For some interlocked yarders, payloads in downhill yarding at low speeds may be considerably less than those predicted with *safe' tensions because these yarders rely on engine braking to dissipate energy..

Load Tests on Tubular Piles in Coralline Strata

At a coral reef site on the Red Sea coast of Saudi Arabia, load tests were performed on 1,422 mm diam tubular steel piles to verify pile design compression and tension capacities predicted by calculations. Although two tests were planned at separate site locations, five were performed (two on test pile A, and three on test pile B) due to the test results disproving some of the calculation assumptions. Test pile A was installed open‐ended and the test results concluded: For a coring pile, the measured compression capacities had reasonable agreement with those calculated (calculatedoverestimates=5.2% and 16.3%); and the design assumption that a soil plug would form was disproved. Test pile B was installed with a structural plug fitted to the leading end and the test results concluded: (1) The measured skin friction at 11mpenetration=zero; and the unit end bearing capacity assumed in the calculations was considerably larger than that measured in the tests at 11 m and 30 m penetration (calculatedoverestimates=181% and 164%).

Adsorption of triethanolamine at the solution/mercury and the solution/air interface

Comparison of adsorption of triethanolamine at the Hg/solution and the air/solution interface has been carried out by means of interfacial and surface tension and differential capacity measurements. Adsorption is stronger at the metal/solution interface than at the free surface of the solution. This is explained in terms of some metal—adsorbate specific interaction. Adsorption parameters for the Hg/solution interface indicate that the adsorbate molecules interact with neighbouring water molecules. While the flat orientation of the large organic molecule does not change with electrode charge, the functional OH groups, slightly turned to the solution, are very likely to rotate under the action of the electrode potential thus giving rise to a field dependent inner layer capacity, C 1.

Yield of white clover and its fixation of nitrogen as influenced by nutritional and soil factors under controlled environment conditions

AbstractWhite clover (Trifolium repens L. cv. Blanca) was grown in 21 UK soils. Yield and N concentration in the herbage (leaf + petiole) were determined at six successive harvests and were related to the supplies of major nutrient elements (as indicated by analysis of the herbage) and to various soil properties. The amount of N2 fixed was estimated by subtraction of the soil N supply from the total amount in the clover.The results suggest that critical concentrations (i.e. concentrations just less than those required for maximum growth) of K, Ca and S in the leaf + petiole after 4 weeks regrowth were approximately 1.4%, 1.3% and <0.16% respectively. The relationship between herbage yield and concentration of N suggests a critical concentration in leaf + petiole of about 3.5% N; lower values probably reflect sub‐optimum rates of N2 fixation and higher values, a restriction of clover growth per se. A reduction in herbage yield attributable to deficiency of K and/or Ca appeared to occur on some soils at harvests 5 and 6, but for any one soil, yield changed little between harvests 2 and 4 inclusive. Differences in herbage yield and in the amount of N2 fixed over this period were, therefore, examined in relation to various soil properties. Significant positive correlations were obtained between herbage yield and contents of clay, organic matter, water content at 100 cm tension and cation exchange capacity. The amount of N2 fixed was less closely correlated than was herbage yield with these soil properties.

Investigation of the Hg/HCl aq. system by capillary electrometers based on maximum bubble pressure method and by classical capillary electrometer: Comparison of interfacial tension and double-layer capacity data

The Hg/HCl aq. system was studied using capillary electrometers based on the maximum bubble pressure principle (that employed either an inverted capillary or a vertical capillary) and by the classical capillary electrometer. All three versions of the capillary electrometer yielded interfacial tension data of high precision, except that the modified capillary electrometer with a vertical capillary and the classical electrometer gave data of slightly lower quality over a narrow range of extreme negative polarization for 0.01 M HCl solution. Based on the electrocapillary and double-layer capacity measurements carried out on identical HCl solutions (0.01 M–1 M), it is shown that there exists a very good correspondence between the measured and derived quantities as compared to the agreement previously observed by Bockris and co-workers (who employed a classical capillary electrometer in their interfacial tension measurements).

Relative tension and potential excursion of muscles in the forearm and hand

Muscle strength varies enormously from person to person and even from time to time, but the ratio of strength from muscle within the same limb varies much less. The mass or volume of a muscle is proportional to its work capacity, and the fiber length of a muscle is proportional to its potential excursion. By dividing the fiber length into the volume of each muscle, the cross-sectional area of the muscle was determined, and a list of relative tension capacities of forearm and hand muscles was prepared. Although based on a small number of specimens, this list has the first data on forearm and hand muscles which should be of practical use in planning the operation of tendon transfer.

Investigation of the Hg/HCl aq. system by capillary electrometers based on maximum bubble pressure method and by classical capillary electrometer Comparison of interfacial tension and double-layer capacity data

The Hg/HCl aq. system was studied using capillary electrometers based on the maximum bubble pressure principle (that employed either an inverted capillary or a vertical capillary) and by the classical capillary electrometer. All three versions of the capillary electrometer yielded interfacial tension data of high precision, except that the modified capillary electrometer with a vertical capillary and the classical electrometer gave data of slightly lower quality over a narrow range of extreme negative polarization for 0.01 M HCl solution. Based on the electrocapillary and double-layer capacity measurements carried out on identical HCl solutions (0.01 M–1 M), it is shown that there exists a very good correspondence between the measured and derived quantities as compared to the agreement previously observed by Bockris and co-workers (who employed a classical capillary electrometer in their interfacial tension measurements).

General study of the thermophysical properties of alkaline earth metals

Several experimental devices are used to measure the density, surface tension, viscosity, and heat capacity of barium, calcium, and cesium from their melting points to 1800°K. Measurement methods are described and results presented.

A study of the effect of surfactants on electrode processes in molten salts

The effect of various organic substances on cathodic processes in the K,Na∣SCN, K,Li∣NO3, 2Al,Na∣Cl and K,Na,Li,Cs∣Cl melts has been studied by ac polarography, spectroscopic and potentiometric methods as well as by surface tension and differential capacity measurements. It has been shown that adsorption of organic substances on Pt electrodes takes place in the melts at temperatures up to 300°C and that the substances studied should be regarded as surfactants. Some surfactants were used for obtaining aluminium electrodeposits with given properties from the 2Al,Na∣Cl melt.

Voltage-induced reflectivity relaxation of bilayer lipid membranes: on changes of bilayer thickness.

Temporal and voltage-induced changes of reflectivity (R), the optical phase difference in transmitted polarized light, of tension and total capacity of bilayer lipid membrane (BLM) were studied. The membranes were mainly formed from total brain phospholipids (TP) in n-alkanes. 1) Reflectivity of "black" regions of films made of TP in decane and hexadecane decreases by several percent with a time constant (tauR) of about 30 min, whereas that of membranes with hexane and heptane does not depend on time (with an accuracy up to 1--2%). The BLM tension decreases appreciably in the course of time and reaches its steady-state value in tens of minutes after complete blackening of the membrane. 2) Under prolonged (up to tens of minutes) action of voltage (V) no R changes of BLMs with hexane, heptane, and hexadecane were revealed at a noise level of 0.2%. Blms with decane usually respond to voltage application, first by a rapid (jump-like) and then by a slow decrease of R with a value spread from 0.2% to 3%. 3) With higher amplitude and temporal resolutions of the signal (signal averaging method) it can be seen that after voltage jump R decreases down to a new steady-state value: at V = 100 mV, deltaR/R = -(2--4) . 10(-4) and tauR approximately 0.1 msec for BLMs from TP in heptane, and deltaR/R = -(3--6) . 10(-2) and tauR approximately 2 msec for BLMs from oxidized cholesterol in decane. It is shown in the latter case that the great value of deltaR/R is due to the contribution of invisible microlenses. In all the cases deltaR approximately V2. 4) It is concluded that at voltage jump a bilayer first becomes thinner due to volumic compression of its hydrocarbon core; then it spreads with a time constant of the order of 0.1 msec, getting thinner until a new equilibrium state is reached. Complete change of bilayer thickness is detah/h approximately -10(-4) at 100 mV.

Pullout Tests of Piles in Sand

Three pullout tests on two instrumented 24-in. -diameter, steel-pipe piles were performed in a deep sand deposit at Mustang Island, Tex., to determine the tension capacity of a pile and to assess the effects of lateral loading on pullout resistance. Test equipment and procedures are described and results of strain data and load vs pile-top movement are presented. Skin friction parameters are determined from these results. Introduction Pullout tests on open-steel pipe piles in sand were run at Pullout tests on open-steel pipe piles in sand were run at the Shell Oil Co. Tank Battery on Mustang Island, Tex. The map in Fig. 1 indicates the test site. About 5 ft of fill was excavated at the site so that the water table would be at ground surface. Two instrumented test piles were driven and pullout tests were performed before and after lateral loading. Test Equipment and Test Piles Test Setup and Test Piles The test setup and test piles are shown in Fig. 2. Two reaction beams, one on each side of the test pile, rested on timber mats. Two hydraulic jacks with pumping units and pressure gauges rested on the reaction beams. A 10-ft pressure gauges rested on the reaction beams. A 10-ft section of 24-in.-diameter pile was specially made and welded to the top of the test pile. Two small-diameter piles were driven to support deflection gauges used to piles were driven to support deflection gauges used to measure movement of the pile top. Cables from deflection and strain gauges were run from the pile to the instrumentation system housed in a van parked beside the excavated area. Two test piles were manufactured from seamless steel pipe (ASTM A-53, Grade B) with 24-in. OD. The wall pipe (ASTM A-53, Grade B) with 24-in. OD. The wall was 3/8-in. thick and weighed 94.6 lb/ft. The piles were composed of a 10-ft loading section, a 32-ft instrumented section, and 38-ft anchor section (Fig. 2). The instrumented section was sealed off by diaphragms at the top and bottom of the section to prevent moisture from damaging the strain gauges. Wires from these gauges were passed through pressure-packing glands in the diaphragm at the top of the instrumented section. Each pile had 40 strain gauges - 34 active and 6 unstrained dummies. The 120-ohm strain gauges were 0.50- x 0.50-in. metal foil. Strain-gauge spacing in the 32-ft section is indicated in Fig. 2. Both test piles were driven with a Delmag-12 diesel hammer. The 38-ft open-ended, uninstrumented section was driven until its top was about 3 ft above the soil surface. Next, the soil plug inside the section was augered out completely to keep it from driving against the diaphragm in the bottom of the 32-ft instrumented section. After welding the 32-ft section to the 38-ft section, driving was resumed and the pile was driven to grade, with the pile flange approximately I ft above the soil surface. The pile was embedded 69 ft. Measurement of Load, Strain, and Deflection During the pullout tests, readings were taken of the applied load, the deflection of the top of the pile, and the axial strain along the pile. The applied load was obtained by reading bourdon-tube pressure gauges that measured the hydraulic pressure in the jacks. The pile deflection was obtained from dial indicators and by use of lineardisplacement transducers. Output from the displacement transducers and from strain gauges was recorded with a digital recording system. JPT P. 343