Equivalent Velocities Research Articles

A WIYN Lithium Survey for Young Stars in the λ Orionis Star-Forming Region

We have found 72 pre–main-sequence (PMS) stars near the center of the λ Orionis star-forming region by spectroscopically testing a magnitude-limited sample for the presence of lithium λ6708 absorption, a diagnostic of youth. All of these stars show large lithium equivalent widths and radial velocities consistent with Orion membership, but only two were discovered previously via Hα or X-ray surveys. Comparison with PMS evolutionary tracks show that the low-mass star formation did not begin prior to the initiation of high-mass star formation 5–7 Myr ago. However, the subsequent detailed star formation history is model dependent. Baraffe et al. isochrones imply that high- and low-mass stars began to form together 5–7 Myr ago, with the low-mass stellar formation ceasing abruptly 1 Myr ago. On the other hand, D'Antona & Mazzitelli isochrones indicate a narrow spread of PMS ages, which suggests a burst of low-mass star formation 1–2 Myr ago. Furthermore, kinematic arguments require that the parent molecular cloud gravitationally bound the stars together until recently, but at present the requisite gas mass is not visible. This leads us to conjecture that both the high- and low-mass stars were in a tightly bound cluster until a supernova blast about 1 Myr ago disrupted the parent cloud. This supernova also impacted on the PMS formation process by either (1) ceasing formation through removal of the gas supply or (2) triggering star births via cloud compression, depending on choice of stellar evolution models. Finally, we find that despite their youth, only four of the 72 PMS stars have T Tauri–like Hα emission, suggesting the absence of accretion disks. We conjecture that this may be the result of photoevaporation of the disks while the low-mass stars were in much closer proximity to the OB stars prior to becoming gravitationally unbound.

Resolving the Intrinsic CivAbsorption in the Seyfert 1 Galaxy NGC 3516

We observed the Seyfert 1 galaxy NGC 3516 with the Goddard High Resolution Spectrograph on the Hubble Space Telescope, and obtained UV spectra at a resolution of about 20,000 in the redshifted C IV 1549 region. The intrinsic C IV absorption in the core of the broad emission line is resolved for the first time into four distinct kinematic components, which are all blue-shifted relative to the systemic radial velocity of the host galaxy. Two components are narrow (20 and 30 km/sec FWHM) and at small radial velocities (-90 and -30 km/sec respectively), and could arise from the interstellar medium or halo of the host galaxy. The two broad components are centered at radial velocities of -380 and -150 km/sec, have widths of 130 and 210 km/sec (FWHM) respectively, and most likely arise in outflowing gas near the active nucleus. The cores of the broad C IV absorption components are very close to zero intensity, indicating that the absorption regions are extended enough to completely occult the broad C IV emitting region (which is ~9 light days in extent). The total column density of the C IV absorption is substantially larger than that measured by Kriss et al. (1996a) from contemporaneous HUT spectra, but we agree with their conclusion that the UV absorption is too strong to arise primarily from the X-ray warm absorber region. The GHRS observations separated by six months reveal no appreciable changes in the equivalent widths or radial velocities of any of the absorption components. At present, we know of two Seyfert galaxies, NGC 3516 and NGC 4151, with complex multiple absorption zones that can remain stable in column density and velocity field over time scales of months to years.

A portable flow chamber forin situdetermination of benthic metabolism

1. Many stream ecologists are interested in determining the metabolic rates of benthic organisms, particularly those of production and respiration. It is often necessary to make these measurements on fresh material in the field at remote sites. Recirculating chambers are commonly used for this purpose.2. A broad variety of recirculating chambers are described in the literature, but each design has inherent limitations. The most common are inability to control flow in the chamber and match it with external flow rates, and a lack of the power required to do this for extended periods. Alteration of spectral irradiance, temperature rise and elevated internal chamber pressures are additional limitations that have received little attention.3. We have designed and constructed a flow chamber that eliminates some of these problems. The chamber utilizes a DC motor‐driven propeller as an efficient recirculator (axial impeller), minimizing power requirements and it is constructed of UVB transparent acrylic to allow a full spectral complement of solar irradiance in the interior. Modular components allow the chamber to be taken apart quickly for cleaning and replacement of parts, making it more functional than some previous designs.4. The axial impeller chamber was compared to a similar sized conventional chamber that had a small diameter return line and a high capacity centrifugal pump. The axial impeller chamber had less of a temperature rise during field incubations, lower power consumption and less internal pressure in the return line when producing equivalent water velocities.5. The reported axial impeller design had relatively homogeneous velocity across the working section relative to other chambers and was capable of water velocities in excess of 1 m s–1.

ESTIMATED OXYGEN CONSUMPTION OF RETRO-LOCOMOTION 637

Retro-locomotion (RL) is commonly used for sport specific conditioning, injury prevention and rehabilitation. Higher energy expenditures (VO2) have been reported for RL as compared to forward locomotion at equivalent velocities. The purpose of the study was to determine VO2 for RL and calculate regression equations for estimating energy expenditure for RL velocity. Forty-eight subjects (M=16, F=32, 28.1 yr ± 2.45) were familiarized with RL on both track and treadmill (TM) for a total of 60-90 min dispersed over 2-4 wk. Following familiarization, subjects completed discontinuous GXT's on a TM. Each stage was 4 min in length, allowing subjects to achieve steady state. TM velocity began at 2.0 mph and was increased by 0.5 to 1.0 mph/stage based upon subject tolerance. Velocity ranges were 2.0-4.5 and 2.5-7.5 mph for retro-walking and retro-running respectively. Regression analyses were performed using measured VO2(ml·kg-1·min-1) and velocity (mph). The following equations for estimating VO2 were calculated: Retro-walking Y=17.786 - 7.26 X + 2.565 X2; Retro-running Y=5.82 X + 8.37, Y: VO2(ml·kg-1·min-1), X: Velocity (mph). Retro-walking r and r2 were.9 (p <.01) and.81 respectively; for retro-running corresponding values were.76 (p <.01) and.57 respectively. The formulae may be useful to more precisely design conditioning programs to improve or maintain performance.

Near infrared low-resolution spectra of 7 Be stars and AG Car

We present and discuss spectra of 7 poorly-studied Be stars and of one Luminous Blue Variable (AG Car), and give equivalent widths and radial velocities of selected spectral lines.

Faint Object Spectrograph Observations of MRK 509: Ultraviolet Absorption Lines Near the Redshift of the Seyfert Galaxy

view Abstract Citations (11) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Faint Object Spectrograph Observations of MRK 509: Ultraviolet Absorption Lines Near the Redshift of the Seyfert Galaxy Crenshaw, D. Michael ; Boggess, Albert ; Wu, Chi-Chao Abstract Ultraviolet spectra of the Seyfert 1 galaxy Mrk 509 have been obtained with the Faint Object Spectrograph on the Hubble Space Telescope. The spectra show strong absorption lines in the cores of the redshifted emission lines of Lyα and C IV λλ1548.2, 1550.8, confirming an earlier detection in IUE high-dispersion spectra, and a new detection of strong N V λλ1238.8, 1242.8 absorption lines, also near the redshift of Mrk 509. There is no evidence for absorption in the lines of Mg II or Si IV at the redshift of Mrk 509. The absorption lines have two components that are at the same velocities as those in the IUE observations obtained - 12 yr earlier: one at the systemic redshift of the host galaxy, as defined by the low-ionization emission lines in the optical, and one at a radial velocity of -390 km s^-1^ relative to the systemic redshift. The equivalent widths and velocities of the absorption lines indicate that they arise from an extended region of highly ionized gas surrounding the nucleus of the host galaxy consisting of two distinct kinematic components. Publication: The Astronomical Journal Pub Date: September 1995 DOI: 10.1086/117582 Bibcode: 1995AJ....110.1026C Keywords: GALAXIES: SEYFERT; QUASARS: ABSORPTION LINES; GALAXIES: INDIVIDUAL: MRK 509 full text sources ADS | data products SIMBAD (4) MAST (2) NED (1) INES (1) ESA (1)

O I lamba 7774 absorption as a tracer of streams and disks in nondegenerate binary stars

view Abstract Citations (16) References (53) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS OI Lambda7774 Absorption as a Tracer of Streams and Disks in Nondegenerate Binary Stars Etzel, Paul B. ; Olson, Edward C. ; Senay, Matthew C. Abstract We propose a new spectroscopic approach for observing circumstellar matter in binary stars, based on the neutral oxygen lambda 7774 absorption lines. We present oxygen equivalent widths and radial velocities in 20 nondegenerate eclipsing binaries. We note limitations and advantages of using this line to trace circumstellar matter in binary systems, and confirm the presence of streams and rotating accretion disks in a number of short- long-period Algol systems. We discuss evidence for geometrically thick disks, and describe a small radial infall superimposed on disk rotation in most long-period systems. We speculate that infall may be related to viscous dissipation in disks. We emphasize the great sensitivity of lambda 7774 in studying the kinematics of circumstellar matter in many nondegenerate binary stars. Publication: The Astronomical Journal Pub Date: March 1995 DOI: 10.1086/117359 Bibcode: 1995AJ....109.1269E Keywords: Absorption Spectra; Accretion Disks; Eclipsing Binary Stars; Oxygen; Radial Velocity; Stellar Envelopes; Stellar Winds; Extinction; Spectral Line Width; Spectrographs; Spectrum Analysis; Stellar Orbits; Astronomy; BINARIES: VISUAL; CIRCUMSTELLAR MATTER; ACCRETION DISKS full text sources ADS | data products SIMBAD (21) CDS (1)

Radial velocities of very low mass stars and candidate brown dwarf members of the Hyades and Pleiades, 2

view Abstract Citations (35) References (54) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radial Velocities of Very Low Mass Stars and Candidate Brown Dwarf Members of the Hyades and Pleiades. II. Stauffer, John R. ; Liebert, James ; Giampapa, Mark Abstract We have determined H alpha equivalent widths and radial velocities with 1 sigma accuracies of approximately 5 km/s for approximately 20 candidate very low mass members of the Pleiades cluster and for a few proposed very low mass members of the Hyades. Most of the Pleiades targets were selected from the recent Hambly, Hawkins, and Jameson proper motion survey, where they were identified as probable Pleiades brown dwarfs with an age spread from 3 to 70 Myr. Our spectroscopic data and a reinterpretation of the photometric data confirm that these objects are indeed likely Pleiades members; however, we believe that they more likely have masses slightly above the hydrogen burning mass limit and that there is no firm evidence for an age spread amongst these stars. All of the very low mass Pleiades and Hyades members show H alpha in emission. However, the ratio of H alpha flux to biometric flux in the Pleiades shows a maximum near MBol approximately equal to 9.5 (M approximately equal to 0.3 solar mass) and a sharp decrease to lower masses. This break occurs at the approximate mass where low mass stars are expected to become fully convective, and it is tempting to assume that the decrease in H alpha flux is caused by some change in the behavior of stellar dynamos at this mass. We do not see a similar break in activity at this mass in the Hyades. We discuss possible evolutionary explanations for this difference in the H alpha activity between the two clusters. Publication: The Astronomical Journal Pub Date: January 1995 DOI: 10.1086/117273 Bibcode: 1995AJ....109..298S Keywords: Brown Dwarf Stars; H Alpha Line; Pleiades Cluster; Radial Velocity; Stellar Mass; Stellar Evolution; Stellar Spectrophotometry; Astrophysics; OPEN CLUSTERS AND ASSOCIATIONS: GENERAL; STARS: LOW MASS; STARS: BROWN DWARFS full text sources ADS | data products SIMBAD (35)

Radial velocities of very low mass stars and candidate brown dwarf members of the Hyades and Pleiades

view Abstract Citations (54) References (63) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radial Velocities of Very Low mass Stars and Candidate Brown Dwarf Members of the Hyades and Pleiades Stauffer, John R. ; Liebert, James ; Giampapa, Mark ; Macintosh, Bruce ; Reid, Neill ; Hamilton, Donald Abstract We have determined H alpha equivalent widths and radial velocities with 1 sigma accuracies of approximately 5 km s-1 for approximately 20 candidate very low mass members of the Hyades and Pleiades clusters. The radial velocities for the Hyades sample suggest that nearly all of these stars are indeed highly probable members of the Hyades. The faintest stars in the Hyades sample have masses of order 0.1 solar mass. We also obtained radial velocities for four candidate very low mass members of the Pleiades and two objects that are candidate BD Pleiads. All of these stars have apparent V magnitudes fainter than the Hyades stars we observed, and the resultant radial velocity accuracy is worse. We believe that the three brighter stars are indeed likely very low mass stellar members of the Pleiades, whereas the status of the two brown dwarf candidates is uncertain. The Hyades stars we have observed and the three Pleiades very low mass stars are the lowest mass members of any open cluster whose membership has been confirmed by radial velocities and whose chromospheric activity has been measured. We see no change in chromospheric activity at the boundary where stars are expected to become fully convective (M approximately equals 0.3 solar mass) in either cluster. In the Pleiades, however, there may be a decrease in chromospheric activity for stars with (V-I)K greater than 3.5 (M less than or equal to 0.1 solar mass). Publication: The Astronomical Journal Pub Date: July 1994 DOI: 10.1086/117054 Bibcode: 1994AJ....108..160S Keywords: Astronomical Spectroscopy; Dwarf Stars; Radial Velocity; Star Clusters; Stellar Spectra; Charge Coupled Devices; Pleiades Cluster; Stellar Mass; Astrophysics; OPEN CLUSTERS AND ASSOCIATIONS: INDIVIDUAL: HYADES; OPEN CLUSTERS AND ASSOCIATIONS: INDIVIDUAL: PLEIADES; STARS: BROWN DWARFS full text sources ADS | data products SIMBAD (33)

Locomotor patterns and costs as related to body size and form in teiid lizards

Stride parameters and gaits were examined in seven species of teiid lizards in an attempt to understand size‐dependent variation of locomotor patterns. Scaling of body dimensions to body mass revealed that axial measures conformed to geometric similarity, whereas the limb segments exhibited an allometry which was statistically significantly less than geometric similarity. Variations in the relationships between stride lengths, stride frequencies and duty factors (% of the stride that foot contacts ground) represented locomotor specializations and were not strictly size‐dependent among species. At body length equivalent velocities, stride length and stride frequency scaled to body mass0.40±0.06 and 0.09±0.03, respectively. Cost during locomotion at body length equivalent velocities could be estimated by the square of the product of stride length and stride frequency. Plotting the cost during locomotion for geometrically similar lizards against body mass yielded an estimate of the cost during locomotion that was proportional to mass0.62±0.11. An estimate of the mass‐specific cost during locomotion at body length‐equivalent velocities scales to mass−0.38±0.11. Because the limbs of these lizards exhibit an allometry less than geometric similarity, a correction of the estimate of the mass‐specific cost during locomotion could be obtained by factoring in the effect of increased locomotor costs associated with relatively shorter pelvic limbs in larger lizards. The allometrically corrected estimate of the mass‐specific cost during locomotion was proportional to mass−0.31. This estimated regression, which is the relatiue cost of transport for a single, morphologically conservative family of lizards, predicts a slope quite close to that derived from studies of oxygen requirements during locomotion in lizards of several families (slope= ‐0.28, John‐Alder, Garland &amp; Bennett, 1986) and in mammals (slope= ‐0.32, Taylor, Heglund &amp; Maloiy, 1982).

地震動を受ける原子炉建屋耐震壁の挙動に関する研究 : (その1)RC造立体耐震壁の静的および仮動的実験

Mechanic and response characteristics of three dimensional reinforced concrete shear walls under the earthquakes are studied through static tests and pseudo dynamic tests performed on the walls in the shapes of a box and a cylinder. In behavior of the walls after the ultimate strength, the box walls shows brittleness while the cylinder walls shows much of toughness. The load-deformation relationship and the principal strain distribution in the 3-D nonlinear FEM analysis agree well with the test results. It is confirmed in the pseudo dynamic tests that wall shapes and input seismic waves have influences on the response behaviors while they have no influence on the equivalent velocities V_E, up to the ultimate strength, which remain almost constant.

Active region mass motions observed in soft X-ray lines

Significant coronal mass motions are deduced from soft X-ray line broadening observed in solar active regions even during quiescent periods. A large data base of Mg XI resonance line profiles near 9.17 A has been acquired with the SMM Flat Crystal Spectrometer for a variety of active region conditions and disk locations. For the X-ray bright areas, the typical profiles have an excess line width equal to or greater than the thermal Doppler width for Mg ions at the observed coronal temperatures (3-4 MK). The equivalent excess velocities of 40-60 km/s are higher than those reported previously for cooler lines in other wavebands. The excess velocities show a correlation with magnetic field strength or gradient, but no obvious dependence on the angular distance from sun center.

Outside-eclipse H-alpha spectra of five eclipsing binaries

H∞ region spectra for five binary systems ϵ Aur, ζ Aur, 31 Cyg, 32 Cyg and 22 Vul, were obtained using the 1m refractor coudé spectrograph of Yunnan Observatory and the 2.1m coudé Reticon of McDonald Observatory, with a dispersion of about 9 A/mm in both cases. All observations were taken outside eclipse. After reduction we obtained the equivalent widths and radial velocities of the H∞ line. Short time scale variations in the H∞ emission were shown in ϵ Aur. The profiles of 31 Cyg and 32 Cyg were found to be very similar.

Polymer degradation in porous media flow

AbstractThe hydrodynamic degradation of high molecular weight poly(acrylamide‐co‐Na acrylate) in 1M NaCl in porous media flow was studied as a function of polymer concentration in the dilute and semidilute concentration ranges. Porous media rheometry was used to monitor molecular weight changes due to chain scission. At equivalent superficial velocities of flow through a glass bead pack, polymers at dilute concentrations showed greater loss of molecular weight than polymers at semidilute concentrations.

Enzymatic properties of a proteolytically nicked RNA polymerase of bacteriophage T7.

The RNA polymerase of bacteriophage T7 is sensitive to cleavage by a protease associated with the membrane fraction of many strains of Escherichia coli. A major degradation product is a T7 RNA polymerase that is proteolytically cleaved between amino acids 172 (lysine) and 173 (arginine) (Tabor, S., and Richardson, C.C. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 1074-1078). The cleavage splits the enzyme into a large fragment (Mr approximately 75,000) and a small fragment (Mr approximately 23,000) which remain tightly associated during the purification of nicked RNA polymerase. The protein retains RNA polymerase activity, but specific activity is reduced 3.5-fold. The proteolytic cleavage also reduces the Mg2+ requirements, increases the apparent Michaelis-Menten constants for the utilization of the ribonucleoside 5'-triphosphates, increases the temperature sensitivity, increases the sensitivity to inhibition by heparin, and increases the probability that a transcript will not be removed from the template. The reduced activity of nicked T7 RNA polymerase is apparently a consequence of inefficient initiation and premature termination. Nicked T7 RNA polymerase successfully initiates at the phi 10 promoter at half the efficiency of native T7 RNA polymerase. Transcripts synthesized by the nicked enzyme are also significantly shorter than transcripts synthesized by the native enzyme. In contrast, nicked T7 RNA polymerase and T7 RNA polymerase exhibit equivalent poly(dI).poly(dC)-dependent activity and equivalent polymerization velocities (60 bases/s at 25 degrees C).

Velocity selectivity in the cat visual system. III. Contribution of temporal factors.

In 149 units from area 17 and 48 units from area 18 the responses to stationary stimulation of different durations were compared with the responses to the same stimulus (a 0.3 degrees-wide light or dark bar) moving at different velocities. The aim was to test the hypothesis that the range of effective velocities depends on the time needed for the bar to cross the receptive field. Forty-two percent of the area 17 cells and 8% of the area 18 cells responded poorly or not at all to briefly presented stationary stimulation. These cells were unable to respond at high velocities, and for these "duration-sensitive" cells the velocity characteristics are well predicted on the basis of responses to stationary stimulation of different durations. Cells that responded equally well to periods of stationary stimulation ranging from 12.5 to 3,200 ms ("duration-insensitive cells") were found to be able to respond at all equivalent velocities, but their preference for either high, low, or intermediate velocities was not reflected in differences in responsiveness to the different durations tested. Duration-sensitive cells in area 17 tended to have a receptive field near the area centralis, and 73% of them were classified as S-family cells, one third being end-stopped S-cells. In contrast only 18% of the duration-insensitive cells were of the S family, and these S-family cells were rarely end-stopped (1/12) or rarely had receptive fields within 5 degrees of the fovea (3/12). Duration-sensitive cells had very long latencies (median 285 ms) in response to a stationary flashed light bar of 1 s duration but much shorter latencies (median 91 ms) when tested with a slowly moving light bar. This difference was not seen in duration-insensitive cells (median latencies = 61 and 59 ms). The ability to respond at high velocity was contrast dependent. At a low contrast level all cells failed to respond to brief stimulation, whether moving or stationary. At high contrast levels only the duration-insensitive cells showed an increased responsivity to brief stimuli. The absence of responses in duration-sensitive cells to brief stimuli of high contrast may depend upon suppressive influences reaching these cells before the excitatory influences. We conclude that the velocity upper cutoff of most S-family cells with a central receptive field can be predicted from a knowledge of the minimum duration of stationary presentation required for their activation (median ON duration threshold, 200 ms).(ABSTRACT TRUNCATED AT 400 WORDS)

Galaxy mass distribution from gravitational light deflection

view Abstract Citations (153) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Galaxy mass distribution from gravitational light deflection Tyson, J. A. ; Valdes, F. ; Jarvis, J. F. ; Mills, A. P., Jr. Abstract A new technique for measuring galaxy mass, based on the gravitational deflection of light, is described. The method does not require stereoscopic detectability or virial or orbital assumptions and can apply to galaxies of all types. Images from 46,954 galaxies were examined in order to find a particular coherent image distortion associated with gravitational lenses of 11,789 foreground galaxies. The equivalent statistical circular velocities of the galaxies are determined as a function of the mass cutoff radius for the foreground galaxy data set. The 2 sigma upper limit to the average circular velocity is found to be less than 170 km per sec for a mass envelope extending to beyond 50 kpc/h radius. The corresponding total mass limit to this radius is 1.7 x 10 to the 11th solar mass. It is concluded that there is not sufficient mass associated with the individual galaxies to achieve the critical density for closure. Publication: The Astrophysical Journal Pub Date: June 1984 DOI: 10.1086/184285 Bibcode: 1984ApJ...281L..59T Keywords: Cosmology; Galactic Structure; Gravitational Lenses; Mass Distribution; Calibrating; Data Reduction; Distortion; Astrophysics full text sources ADS |

Detection of coherent movement in peripherally viewed random-dot patterns.

We studied the detection of coherent motion in stroboscopically moving random-dot patterns for foveal vision and at eccentricities of 6, 12, 24, and 48 deg in the temporal visual field. Threshold signal-to-noise ratios (SNR's) were determined as a function of velocity for a range of stimulus sizes. It was found that the motion-detection performance is roughly invariant throughout the temporal visual field, provided that the stimuli are scaled according to the cortical magnification factor to obtain equivalent cortical sizes and velocities at all eccentricities. The maximum field velocity compatible with the percept of coherent motion increased about linearly with the width of the square stimuli. At this high-velocity threshold any pixel crossed the field in five to nine equal steps with a constant total crossing time of 50-90 msec, regardless of stimulus size or eccentricity. The lowest SNR values were reached at the optimal or tuning velocity V0. They approached the amazingly low values of 0.04-0.05 for large stimuli and at all eccentricities. Regardless of stimulus size, the parameter V0 increased about linearly with eccentricity from roughly 1 deg sec-1 at the fovea to some 8 deg sec-1 at 48 deg in the temporal visual field.

Measurement of the sulfur dioxide and sulfuric acid aerosol induced corrosion of zinc in a dynamic flow system

A flow reactor and experimental technique were developed to study the variables controlling the SO 2 and H 2SO 4 (aerosol) pollutant induced corrosion of zinc. The experimental technique allowed deposition velocities to be determined for both accumulation mode H 2SO 4 aerosols and SO 2 gas at equivalent frictional velocities, while providing an electrochemical technique to observe corrosion processes in real time. Experimental measurements indicate that the principal factors affecting sulfur pollutant induced corrosion are surface wetness, pollutant flux to the surface and the chemical form of the pollutant. The overall results show that under urban environmental conditions, corrosion damage by SO 2 will dominate over that from H 2SO 4 aerosols.

Mechanics and energetics of lengthening of active airway smooth muscle.

For smooth muscle in general there appears only one report dealing with force-velocity (FV) relationships of active muscle subjected to forcible elongation by application of loads (P) greater than its maximum isometric tetanic tension (Po); for airway smooth muscle (ASM) there is none. Since ASM may be subjected to increasing stretch during inspiration, the relationship is important and was therefore studied with canine tracheal smooth muscle (TSM) as a model. FV data for P less than Po could be fitted by Hill's hyperbolic equation. For P greater than Po, lengthening velocity was greater than predicted by the equation. However at equivalent velocities, the muscle during elongation could support a load three times greater than during shortening; in this it resembled skeletal muscle. From this it may be speculated that distension of the airway during inspiration would not be associated with mechanical instability. With reference to energy requirements of the elongating TSM it was shown, as has been for skeletal muscle, that the net rate of energy liberation (assessed by measuring tissue levels of adenosine triphosphate and creatine phosphate) in an elongating active muscle is less than that of a muscle contracting isometrically.