Relative magnitude and asynchrony of directional components of contraction in sedated dog left ventricle

1994 ◽  
Vol 267 (1) ◽  
pp. H75-H84
Author(s):  
A. C. Nolan ◽  
T. Karwoski ◽  
M. J. Potel ◽  
J. M. Rubin ◽  
R. E. Sayre
Keyword(s):  
Relative Magnitude ◽  
Mean Difference ◽  
Segment Length ◽  
Maximum Speed ◽  
Measurement Interval ◽  
Local Anisotropy ◽  
Temporal Relationships ◽  
Speed Of Shortening ◽  
Rapid Contraction ◽  
Made In

The purpose of this study was to quantitate the temporal relationships and the extent and speed of shortening in segments of myocardium responsive to contraction in circumferential, longitudinal, and oblique fiber groups. Measurements were made in five sedated dogs (morphine, diazepam) with and without alterations in preload and afterload (nitroprusside, phenylephrine). The measurement interval was the phase of rapid contraction, determined by differentiation of the segment length vs. time. In the control state, percentage segment shortening was greater in circumferential than in longitudinal [15.2 +/- 0.24 (SE) vs. 10.5 +/- 0.80%; P = 0.0020] and in the subepicardial oblique than in the subendocardial oblique fiber directions (16.6 +/- 0.65 vs. 9.7 +/- 0.36%; P = 0.0010). Shortening was proportional to both maximum speed and duration of shortening (r = 0.735 +/- 0.015 and 0.757 +/- 0.017, respectively). Duration of shortening was significantly longer in circumferential than in longitudinal (mean difference 39.3 +/- 6.6 ms; P = 0.0039) and in subepicardial oblique than in subendocardial oblique directions (mean difference 27.7 +/- 5.5 ms; P = 0.0072). Velocities of up to 3.0 segment lengths/s were attained in response to nitroprusside. These data reveal the local anisotropy and asynchrony of contraction in the myocardium; however, they also support the concept of the myocardium as a functional continuum. The dominance of circumferential over longitudinal and subepicardial over subendocardial oblique contractile components indicates their relative contributions to the constriction of the midmyocardial shell.

scholarly journals Effect of type of road humps on vehicular speeds on residential roads

2018 ◽  
Vol 181 ◽  
pp. 04002
Author(s):  
Leksmono Suryo Putranto ◽  
Kevin Kurniawan
Keyword(s):  
Data Collection ◽  
Mean Difference ◽  
Statistical Analyses ◽  
Maximum Speed ◽  
Speed Reduction ◽  
The Road ◽  
Road Segments ◽  
Made In

To reduce potential pedestrian fatalities, in residential road maximum speed is 30km/hour. Apart from installing maximum speed signs, installing road humps may ensure speed reduction. This paper is intended to compare light vehicles and motorcycles speeds and speeds reductions due to road humps. Data collection was done in Modernland, Tanggerang City. Two road segments were observed, i.e. segments with standard and non-standard road humps. Observation was made in morning, noon and afternoon periods. A portable speed gun was used to measure the speed at about 50m and 25m before the road humps. Some mean difference statistical analyses were conducted for both speeds and speeds differences between different type of road humps and between pairs of observation periods. The 0.05 significant level was used. Surprisingly, mean of speeds differences (50m vs 25m) in standard road hump is significantly higher than in non-standard road hump.

Maximum shortening speed of motor units of various types in cat lumbrical muscles

1993 ◽  
Vol 69 (2) ◽  
pp. 442-448 ◽  
Author(s):  
J. Petit ◽  
M. Chua ◽  
C. C. Hunt
Keyword(s):  
Motor Unit ◽  
Inverse Correlation ◽  
Motor Units ◽  
Maximum Speed ◽  
Single Motor Units ◽  
Maximal Speed ◽  
Contraction Times ◽  
Isometric Twitch ◽  
Lumbrical Muscles ◽  
Speed Of Shortening

1. Isotonic shortening of cat superficial lumbrical muscles was studied during maximal tetanic contractions of single motor units of identified types. For each motor unit, the maximal speed of contraction, Vmax, was determined by extrapolating to zero the hyperbolic relation between applied tension and speed of shortening. 2. The maximal speeds of shortening of motor units formed a continuum with the highest velocities observed for the fast fatigable motor units and the lowest for the slow motor units. 3. On average, the maximum speed of shortening increased with the tetanic tension developed by the motor units. 4. In motor units with isometric twitch contraction times less than 35 ms, these times showed a significant inverse correlation with Vmax. Progressively longer contraction times were associated with rather small changes in Vmax. 5. The implications of these findings on the speed of muscle shortening during motor-unit recruitment are discussed.

Patterns of gene flow between Negroes and whites in the US

1976 ◽  
Vol 8 (4) ◽  
pp. 309-333 ◽  
Author(s):  
K. F Dyer
Keyword(s):  
Economic Status ◽  
Significant Proportion ◽  
Relative Magnitude ◽  
Genetic Evidence ◽  
White Female ◽  
Negro Male ◽  
American Colonies ◽  
The Us ◽  
Total Magnitude ◽  
Made In

SummaryA review of the pattern and magnitude of nero–white mating in the US is presented from the time of the earliest arrival of negroes in the American colonies until the present, using historical, demographic, census and genetic evidence.The relative magnitude of negro male–white female matings compared to the converse are analysed in view of the different genetic outcomes of these two types of mating for X-linked genes. Contrary to many strongly stated opinions it is conclued from the historical evidence that, even from the earliest days of slavery, negro male–white female matings were a significant proportion of all negro–white matings. Census and demographic evidence suggests that their frequency increased so that from the time of the Civil War on they have formed a majority of inter-racial matings.Genetic evidence based on estimates of the amout of admixture of white genes in a number of negro populations is considered. Estimates of admixture for the X-linked genes G6PD, and those for colour blindness are as high or higher than those derived from comparable autosomal genes.Some observations on the total magnitude of negro–white mating, on the phenomenon of passing and on the relative socio-economic status of those involved are also made.The implication of the findings on these phenomena for investigations and hypotheses concerning differences in intelligence and intellectual abilites between the races, particulary spatial ability which is thought to be strongly influenced by a gene on the X chromosome, are considered.It is concluded that some of the assumptions made in proposing hypotheses regarding the origin and distribution of these abilities in the American negro are at variance with genetic, historical and sociological findings.

ON THE THEORY OF FLOW OF UNDERGROUND FLUIDS IN COMPRESSIBLE STRATA

1959 ◽  
Vol 37 (3) ◽  
pp. 276-284
Author(s):  
A. E. Scheidegger
Keyword(s):  
Porous Medium ◽  
Vertical Direction ◽  
Complex Problem ◽  
Flow Equation ◽  
Local Anisotropy ◽  
Local Isotropy ◽  
Differential Flow ◽  
Considerable Simplification ◽  
General Geometry ◽  
Made In

The problem of flow of a fluid within a compressible porous medium is investigated. It is shown that in general, the motion of the fluid cannot be separated from that of the medium. This leads to a very complex problem of consolidation. However, considerable simplification can be made in applications to the flow of underground fluids. In that case, the general geometry of the consolidation can be predicted since the latter can take place in the vertical direction only. Furthermore, in many cases it is possible to neglect the volume compressibility of the porous matrix.Two cases have been considered: that of local isotropy of stress and permeability and that of local anisotropy of these two quantities. The basic differential flow equation for the two cases is deduced.

scholarly journals RATTAN DIVERSITY AND BROAD EDAPHIC NICHES IN A TROPICAL RAINFOREST OF BUTON, SULAWESI, INDONESIA

REINWARDTIA ◽  
2016 ◽  
Vol 15 (2) ◽  
pp. 99
Author(s):  
ROSIE PRITCHETT ◽  
AURORA PHILLIPS ◽  
ANI MARDIASTUTI ◽  
ANDREW POWLING
Keyword(s):  
Correspondence Analysis ◽  
Soil Ph ◽  
Tropical Rainforest ◽  
Mean Difference ◽  
Weak Version ◽  
Ph Values ◽  
Wide Range ◽  
Show Evidence ◽  
Made In

PRITCHETT, R., PHILLIPS, A., MARDIASTUTI, A. & POWLING, A. 2016. Rattan diversity and broad edaphic niches in a tropical rainforest of Buton, Sulawesi, Indonesia. Reinwardtia 15(2): 99 – 110. — This paper attempts to answer the question: how can at least 20 species of rattan palms in the genus Calamus (family Palmae (Arecaceae)) co -exist in a rainforest? A survey of rattans was made in Lambusango Forest on Buton, an island close to south east Sulawesi, in Indonesia. Rattan species and numbers were recorded in 87 quadrats of 30 × 10 m, laid out along linear transects in habitats with a variety of soils. Evidence for edaphic (soil) niches was sought. Different rattan species were found to be adapted to soils with different conductivity and pH values. Standardised mean difference (d) scores were calculated for pairs of species based on their response to soil pH. Of the 66 pairs tested, 61 were found to be significantly different statistically. Such differences suggest, but do not prove, that many species occupy different edaphic niches. It was found that species which show a preference for soils with intermediate pH values (5.0 to 6.5) can grow in soils with a wide range of pH values, implying broad edaphic niches and that competition between these species is weak. Correspondence analysis shows that many species do not distinguish greatly between many soils with intermediate pH values. It is concluded that rattan species show evidence for having different edaphic niches, although the niches for many species are broad. It is speculated that many rattan species may be ecologically equivalent and that a weak version of ecological neutrality theory may apply.

NOTE ON THE ACCELERATION OF SHIPS

1937 ◽  
Vol 15a (2) ◽  
pp. 15-24
Author(s):  
K. F. Tupper
Keyword(s):  
Maximum Speed ◽  
Ship Speed ◽  
Made In

Calculations were made of the time and distance required for a ship to accelerate to any fraction of its maximum speed, and are intended to serve as a guide in determining the length of run to be made in approaching the measured course in the conduct of ship speed trials. The effect of inaccuracy in the underlying assumptions was examined. Curves and tables are presented and offered as suitable for use.

Force-velocity properties of fatigue-resistant units in cat fast-twitch muscle after fatigue

1987 ◽  
Vol 63 (4) ◽  
pp. 1511-1518 ◽  
Author(s):  
D. D. Hatcher ◽  
A. R. Luff
Keyword(s):  
Recovery Period ◽  
Motor Units ◽  
Isometric Tension ◽  
Maximum Speed ◽  
Control Value ◽  
Force Velocity ◽  
Flexor Digitorum ◽  
Fast Twitch ◽  
Whole Muscle ◽  
Speed Of Shortening

The isometric and force-velocity properties of an identified and uniform population of fast-twitch, fatigue-resistant (FR) fibers within the flexor digitorum longus (FDL) muscle were investigated before, immediately after, and during recovery from a fatiguing repetitive isometric stimulus regime (40 Hz for 330 ms every s for 180 s) in the anesthetized cat. It was necessary to determine the smallest fraction of muscle that had the same force-velocity properties as the whole muscle. This was approximately 15% for FDL; if the fraction was less, the maximum speed of shortening was depressed and the a/Po value increased. Motor units were enlarged by partial denervation of the muscle, causing the intact motoneurons to sprout and incorporate more muscle fibers; FR units showed the greatest increase. Immediately after the fatigue regime, maximum isometric tetanic tension declined to 67% but subsequently recovered to 90% of the control value by the end of the 60-min recovery period. Maximum speed of shortening dropped to 71% of the control but after 30 min had recovered and did not differ significantly from control values. It is concluded that the capacity for recovery from fatigue is greater for FR units than for a whole muscle, which also contains fast-fatiguable units, and that the mechanisms involved in the recovery of the maximum isometric tension and maximum speed of shortening are independently regulated.

Analysis of Lateral Track Strength for High Speed Rail

2005 ◽  
Author(s):  
Steven M. Chrismer
Keyword(s):  
High Speed ◽  
Maximum Speed ◽  
Strength Model ◽  
Vehicle Dynamic ◽  
High Speed Rail ◽  
Independent Analysis ◽  
Load Limit ◽  
Rail Industry ◽  
Passenger Trains ◽  
Made In

Recently the FRA has proposed a reduction in the maximum allowable net axle lateral load limit from the current 50 percent of static vertical axle load (NAL/V limit = 50%) to less than 40 percent depending, in part, on the basis of FRA’s lateral track strength model, TREDA. Such a reduction could indirectly result in limiting the maximum speed of high speed passenger trains to the equivalent of 7 inches (178 mm) cant deficiency. This paper reports on the author’s investigation of selected assumptions and calculations made in TREDA. Improvements to the model are recommended and a revised NAL/V relationship is proposed, derived from an independent analysis of the driving and resisting forces. Finally, a vehicle dynamic analysis is performed to determine how the author’s proposed revised NAL/V limit would affect 9-inch (229 mm) cant deficiency operation as the high speed rail industry is now considering.

scholarly journals Contributions of mobile technologies to addiction research

2016 ◽  
Vol 18 (2) ◽  
pp. 213-221 ◽  
Keyword(s):  
Mobile Technology ◽  
Technology Use ◽  
Life Experiences ◽  
Point Of View ◽  
Mobile Technologies ◽  
Accurate Assessment ◽  
Research Protocols ◽  
Temporal Relationships ◽  
Wide Range ◽  
Made In

Mobile technologies are revolutionizing the field of mental health, and particular progress has been made in their application to addiction research and treatment. The use of smartphones and other mobile devices has been shown to be feasible with individuals addicted to any of a wide range of substances, with few biases being observed concerning the repeated monitoring of daily life experiences, craving, or substance use. From a methodological point of view, the use of mobile technologies overcomes longstanding limitations of traditional clinical research protocols, including the more accurate assessment of temporal relationships among variables, as well as the reduction in both contextual constraints and discipline-specific methodological isolation. The present article presents a conceptual review of these advances while using illustrations of research applications that are capable of overcoming specific methodological barriers. Finally, a brief review of both the benefits and risks of mobile technology use for the treatment of patients will be addressed.

scholarly journals Carga interna y externa en el tenis de competición: comparación de tres tipos de entrenamiento (Internal and external load in competitive tennis: comparison of three types of training)

Retos ◽  
2021 ◽  
Vol 44 ◽  
pp. 534-541
Author(s):  
Alberto Rodríguez Cayetano ◽  
Óscar Martín Martín ◽  
Félix Hernández Merchán ◽  
Salvador Pérez Muñoz
Keyword(s):  
Heart Rate ◽  
External Load ◽  
Perceived Exertion ◽  
Training Session ◽  
Maximum Speed ◽  
Internal Load ◽  
Heart Rate Monitors ◽  
Tennis Players ◽  
Rate Of Perceived Exertion ◽  
Made In

  El objetivo principal de esta investigación es cuantificar la carga externa y la carga interna en tres tipos de entrenamiento (cubos con la mano, cubos con raqueta y peloteos) más utilizados en el ámbito del tenis de competición y compararlos entre sí. Participaron 6 jugadores de tenis (cuatro jugadores masculinos y 2 jugadoras) con una media de edad de 16.67 (± 2.73) años. Para cuantificar las cargas, se han utilizado pulsómetros POLAR +M400 para recoger los datos relacionados con la frecuencia cardíaca, distancia recorrida, velocidad media y máxima, y sensores ZEPP TENNIS, con los que se han recogido los datos relativos a tipo de golpe, número de golpeos y velocidad de raqueta en cada uno de los golpes realizados. Además, para registrar la percepción subjetiva de esfuerzo, en cada tarea realizada y al final de cada entrenamiento, se ha utilizado la Escala de Borg CR-10 (Borg, 1982). Se realizaron 9 sesiones de entrenamiento por parejas: tres para el entrenamiento del drive, tres para el entrenamiento del revés y tres para el entrenamiento del drive y el revés de forma conjunta, una para cada tipo de entrenamiento. Los resultados obtenidos muestran que el entrenamiento de cubos con la mano tiene mayor carga interna en cuanto a número de golpeos y velocidad media de raqueta, siendo el entrenamiento de peloteos el que mayor carga externa refleja en relación a velocidades y distancias recorridas. Abstract. The main objective of this research is to quantify the external load and the internal load in three types of training (buckets with the hand, buckets with racket and rallies) most used in the field of tennis and compare them to each other. Six tennis players participated (four male and two female players) with an average age of 16.67 (± 2.73) years. To quantify the loads, POLAR +M400 heart rate monitors were used to collect the data related to heart rate, distance covered, average and maximum speed, and ZEPP TENNIS sensors were used to collect the data related to type of stroke, number of strokes and racket speed for each of the strokes made. In addition, the Borg CR-10 Scale (Borg, 1982) has been used to record the rate of perceived exertion, in each task performed and at the end of each training session. Nine training sessions were carried out in pairs: three for drive training, three for backhand training and three for drive and backhand training together, one for each type of training. The results obtained show that bucket training with the hand has a greater internal load in terms of the number of strokes and average racket speed, with racket training having the greatest external load in relation to speed and distance travelled.

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