Preaggregative cell motion in Dictyostelium

1979 ◽  
Vol 36 (1) ◽  
pp. 281-309
Author(s):  
M.J. Potel ◽  
S.A. Mackay
Keyword(s):  
High Velocity ◽  
Time Course ◽  
Diffusion Constant ◽  
Movement Direction ◽  
Mean Velocity ◽  
Persistence Time ◽  
Mechanical Adhesion ◽  
Cross Correlation Analysis ◽  
Contact Frequency ◽  
The Mean

The motions of a large number (495) of preaggregative D. discoideum NC-4 cells in sparse fields are recorded on time-lapse film and analysed using a specially constructed computer graphics system. All films are produced under a standard set of conditions, so that the range of cell behaviours under given conditions can be characterized. The mean velocity of pre-aggregative D. discoideum NC-4 is 7.19 micrometers/min. The mean velocity time course has a significant early peak at about 3 h. The distribution of mean velocities is fairly broad with a long high velocity tail. A modified random walk model using the parameters diffusion constant and persistence time describes well the changes in cell direction with time. Persistence can be described as an exponentially distributed ‘memory’ of movement direction, with a mean of 4.89 min. High velocity cells never have long persistence times, and persistence time shows no relationship with age. A nearest neighbour model of cell spacing shows that cells are randomly (Poisson) distributed at low densities. Measurements of cell contacts are compared to a simple model of contact frequency based on the kinetic theory of gases to show that cells at low densities have an affinity for making collisions. The length of contact durations is indicative of some mechanical adhesion between cells, and cells in contact move significantly though not dramatically slower. A cross-correlation analysis shows that the various parameters of motion are significantly interrelated in numerous ways. Finally mutants and strains related to D. discoideum NC-4 exhibit a number of new behaviours, suggesting that motion is a distinctive characteristic of cell type.

Modeling fiber arrangement and distribution during the roller drafting process

2019 ◽  
Vol 89 (19-20) ◽  
pp. 4295-4305 ◽  
Author(s):  
Na Sun ◽  
Chongwen Yu ◽  
Jianping Yang
Keyword(s):  
High Velocity ◽  
Linear Density ◽  
Gauge Length ◽  
Mean Velocity ◽  
Point Distribution ◽  
Distribution Form ◽  
Fiber Arrangement ◽  
Spinning Process ◽  
The Mean ◽  
Velocity Motion

During the spinning process, the roller drafting operation plays a significant role in attenuating the sliver to an appropriate linear density. In this study, the model of fiber arrangement was applied to simulating the roller drafting process in order to shed light on the sliver dynamic behavior in the drafting zone. The drafting process was operated from the high-velocity motion of the first accelerated fiber to the high-velocity motion of the last accelerated fiber. The proposed model showed that the simulated sliver attenuation processes were highly corresponded to the actual sliver attenuation results. In addition, the results revealed that the draft ratio, gauge length, input sliver linear density and accelerated-point distribution form had effective influences on the attenuation curves of sliver linear density, whilst the delivery speed scarcely had any effect. The fiber distributions of various forms were also investigated specifically and quantitatively from the fiber arrangement during the drafting procedure in real time. Furthermore, the sliver dynamic was also described by the mean and CV of fiber velocities within the drafting zone. The obtained simulation results demonstrated that the draft ratio, gauge length and delivery speed had a bearing on the mean velocity of fibers, while the CV of fiber velocities was significantly influenced by the draft ratio, gauge length and input sliver linear density. Besides, the distribution pattern has a valuable contribution to the mean and CV of fiber velocities. In consequence, the new drafting model was validated to be effective in quantizing the drafting process.

EARLY VARIATIONS OF PLASMA CORTISOL AFTER PULSE INTRAVENOUS INJECTION OF DIBUTYRYL CYCLIC ADENOSINE 3′,5′-MONOPHOSPHATE IN NORMAL SUBJECTS

1973 ◽  
Vol 72 (4) ◽  
pp. 753-761 ◽  
Author(s):  
Alberto Angeli ◽  
Giuseppe Boccuzzi ◽  
Roberto Frajria ◽  
Daniela Bisbocci ◽  
Franco Ceresa
Keyword(s):  
Intravenous Injection ◽  
Plasma Cortisol ◽  
Time Course ◽  
Healthy Adult ◽  
Normal Subjects ◽  
Adult Women ◽  
Healthy Women ◽  
Adrenal Steroidogenesis ◽  
The Mean ◽  
Zero Time

ABSTRACT 10 mg/kg of dibutyryl cyclic adenosine 3′,5′-monophosphate (Db-cAMP) was iv pulse injected into twelve healthy adult women. The plasma cortisol levels were determined as 11-OHCS at zero time and then at 2.5, 5, 7.5, 10, 15, 30, 60 and 180 min after the injection. The data were compared with those obtained at the corresponding times in two groups of eleven and seventeen healthy women after the injection of 250 ng and 250 μg of synthetic β-1-24 corticotrophin performed in the same manner as the injection of the nucleotide. The mean increments in plasma cortisol were significantly lower after Db-cAMP than after ACTH. Differences were noted by analyzing the time course of the responses. In the case of stimulation with Db-cAMP the 11-OHCS levels rose progressively to a maximum at 15–30 min. By contrast, a peak of plasma cortisol was evident in most cases within a few min after the injection of ACTH; after a fall, a later rise was then observed starting from 15 min. The differences in the plasma 11-OHCS responses after the two stimuli may also be of interest clinically for the investigation of some aspects of adrenal steroidogenesis.

The flow of liquid in a stream from the standard turbine impeller

1979 ◽  
Vol 44 (3) ◽  
pp. 700-710 ◽  
Author(s):  
Ivan Fořt ◽  
Hans-Otto Möckel ◽  
Jan Drbohlav ◽  
Miroslav Hrach
Keyword(s):  
Reynolds Number ◽  
Kinematic Viscosity ◽  
Momentum Flux ◽  
Relative Size ◽  
Mean Velocity ◽  
Axial Profile ◽  
The Mean ◽  
Hot Film ◽  
Turbine Impeller

Profiles of the mean velocity have been analyzed in the stream streaking from the region of rotating standard six-blade disc turbine impeller. The profiles were obtained experimentally using a hot film thermoanemometer probe. The results of the analysis is the determination of the effect of relative size of the impeller and vessel and the kinematic viscosity of the charge on three parameters of the axial profile of the mean velocity in the examined stream. No significant change of the parameter of width of the examined stream and the momentum flux in the stream has been found in the range of parameters d/D ##m <0.25; 0.50> and the Reynolds number for mixing ReM ##m <2.90 . 101; 1 . 105>. However, a significant influence has been found of ReM (at negligible effect of d/D) on the size of the hypothetical source of motion - the radius of the tangential cylindrical jet - a. The proposed phenomenological model of the turbulent stream in region of turbine impeller has been found adequate for values of ReM exceeding 1.0 . 103.

scholarly journals The mean velocity of posterior cerebral artery and basilar artery in Parkinson's disease with sleep disorders

2021 ◽  
Vol 4 ◽  
pp. 100207
Author(s):  
Muhammad Iqbal Basri ◽  
Ida Farida ◽  
Yudy Goysal ◽  
Jumraini Tammasse ◽  
Muhammad Akbar
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Sleep Disorders ◽  
Cerebral Artery ◽  
Basilar Artery ◽  
Posterior Cerebral Artery ◽  
Mean Velocity ◽  
The Mean

scholarly journals Effect of Mean Velocity-to-Critical Velocity Ratios on Bed Topography and Incipient Motion in a Meandering Channel: Experimental Investigation

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 883
Author(s):  
Nargess Moghaddassi ◽  
Seyed Habib Musavi-Jahromi ◽  
Mohammad Vaghefi ◽  
Amir Khosrojerdi
Keyword(s):  
Experimental Investigation ◽  
Critical Velocity ◽  
Velocity Ratio ◽  
Scour Depth ◽  
Incipient Motion ◽  
Mean Velocity ◽  
Straight Path ◽  
Meandering Channel ◽  
Bed Topography ◽  
The Mean

As 180-degree meanders are observed in abundance in nature, a meandering channel with two consecutive 180-degree bends was designed and constructed to investigate bed topography variations. These two 180-degree mild bends are located between two upstream and downstream straight paths. In this study, different mean velocity-to-critical velocity ratios have been tested at the upstream straight path to determine the meander’s incipient motion. To this end, bed topography variations along the meander and the downstream straight path were addressed for different mean velocity-to-critical velocity ratios. In addition, the upstream bend’s effect on the downstream bend was investigated. Results indicated that the maximum scour depth at the downstream bend increased as a result of changing the mean velocity-to-critical velocity ratio from 0.8 to 0.84, 0.86, 0.89, 0.92, 0.95, and 0.98 by, respectively, 1.5, 2.5, 5, 10, 12, and 26 times. Moreover, increasing the ratio increased the maximum sedimentary height by 3, 10, 23, 48, 49, and 56 times. The upstream bend’s incipient motion was observed for the mean velocity-to-critical velocity ratio of 0.89, while the downstream bend’s incipient motion occurred for the ratio of 0.78.

Theoretical analysis of a rolling-sliding elastohydrodynamic lubrication line contact with a subsurface inclusion

2019 ◽  
Vol 233 (8) ◽  
pp. 1197-1207
Author(s):  
Armando Félix Quiñonez ◽  
Guillermo E Morales Espejel
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Element Model ◽  
Von Mises Stress ◽  
Transient Effects ◽  
Mean Velocity ◽  
The Matrix ◽  
Soft Inclusion ◽  
The Mean ◽  
Von Mises ◽  
Fully Coupled

This work investigates the transient effects of a single subsurface inclusion over the pressure, film thickness, and von Mises stress in a line elastohydrodynamic lubrication contact. Results are obtained with a fully-coupled finite element model for either a stiff or a soft inclusion moving at the speed of the surface. Two cases analyzed consider the inclusion moving either at the same speed as the mean velocity of the lubricant or moving slower. Two additional cases investigate reducing either the size of the inclusion or its stiffness differential with respect to the matrix. It is shown that the well-known two-wave elastohydrodynamic lubrication mechanism induced by surface features is also applicable to the inclusions. Also, that the effects of the inclusion become weaker both when its size is reduced and when its stiffness approaches that of the matrix. A direct comparison with predictions by the semi-analytical model of Morales-Espejel et al. ( Proc IMechE, Part J: J Engineering Tribology 2017; 231) shows reasonable qualitative agreement. Quantitatively some differences are observed which, after accounting for the semi-analytical model's simplicity, physical agreement, and computational efficiency, may then be considered as reasonable for engineering applications.

The Estimation of Discharge in an Experimental Open Channel

2014 ◽  
Vol 905 ◽  
pp. 369-373
Author(s):  
Choo Tai Ho ◽  
Yoon Hyeon Cheol ◽  
Yun Gwan Seon ◽  
Noh Hyun Suk ◽  
Bae Chang Yeon
Keyword(s):  
Unsteady Flow ◽  
River Discharge ◽  
Open Channel ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Velocity Equation ◽  
The Mean ◽  
Loop Form

The estimation of a river discharge by using a mean velocity equation is very convenient and rational. Nevertheless, a research on an equation calculating a mean velocity in a river was not entirely satisfactory after the development of Chezy and Mannings formulas which are uniform equations. In this paper, accordingly, the mean velocity in unsteady flow conditions which are shown loop form properties was estimated by using a new mean velocity formula derived from Chius 2-D velocity formula. The results showed that the proposed method was more accurate in estimating discharge, when compared with the conventional formulas.

scholarly journals Statistical Characteristics of Unsteady Storms in Radar Observations for the Beijing–Tianjin Region

2015 ◽  
Vol 54 (1) ◽  
pp. 106-116 ◽  
Author(s):  
Yu Wang ◽  
Hong-Qing Wang ◽  
Lei Han ◽  
Yin-Jing Lin ◽  
Yan Zhang
Keyword(s):  
Warm Season ◽  
Environmental Parameters ◽  
Statistical Characteristics ◽  
Movement Speed ◽  
Movement Direction ◽  
Upper Troposphere ◽  
Maximum Value ◽  
Dynamic Factors ◽  
The Mean ◽  
Wind Profiles

AbstractThis study was designed to provide basic information for the improvement of storm nowcasting. According to the mean direction deviation of storm movement, storms were classified into three types: 1) steady storms (S storms, extrapolated efficiently), 2) unsteady storms (U storms, extrapolated poorly), and 3) transitional storms (T storms). The U storms do not fit the linear extrapolation processes because of their unsteady movements. A 6-yr warm-season radar observation dataset was used to highlight and analyze the differences between U storms and S storms. The analysis included geometric features, dynamic factors, and environmental parameters. The results showed that storms with the following characteristics changed movement direction most easily in the Beijing–Tianjin region: 1) smaller storm area, 2) lower thickness (echo-top height minus base height), 3) lower movement speed, 4) weaker updrafts and the maximum value located in the mid- and upper troposphere, 5) storm-relative vertical wind profiles dominated by directional shear instead of speed shear, 6) lower relative humidity in the mid- and upper troposphere, and 7) higher surface evaporation and ground roughness.

scholarly journals Dynamic Asymmetries Do Not Match Spatiotemporal Step Asymmetries during Split-Belt Walking

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1089
Author(s):  
Stefano Scarano ◽  
Luigi Tesio ◽  
Viviana Rota ◽  
Valeria Cerina ◽  
Luigi Catino ◽  
...  
Keyword(s):  
Lower Limb ◽  
Step Length ◽  
Centre Of Mass ◽  
Mean Velocity ◽  
Rehabilitation Research ◽  
Joint Dynamics ◽  
Stance Time ◽  
After Effect ◽  
The Mean ◽  
Step Parameters

While walking on split-belt treadmills (two belts running at different speeds), the slower limb shows longer anterior steps than the limb dragged by the faster belt. After returning to basal conditions, the step length asymmetry is transiently reversed (after-effect). The lower limb joint dynamics, however, were not thoroughly investigated. In this study, 12 healthy adults walked on a force-sensorised split-belt treadmill for 15 min. Belts rotated at 0.4 m s−1 on both sides, or 0.4 and 1.2 m s−1 under the non-dominant and dominant legs, respectively. Spatiotemporal step parameters, ankle power and work, and the actual mean velocity of the body’s centre of mass (CoM) were computed. On the faster side, ankle power and work increased, while step length and stance time decreased. The mean velocity of the CoM slightly decreased. As an after-effect, modest converse asymmetries developed, fading within 2–5 min. These results may help to decide which belt should be assigned to the paretic and the unaffected lower limb when split-belt walking is applied for rehabilitation research in hemiparesis.

Toroidal plasma configuration with anisotropic pressure

1987 ◽  
Vol 38 (2) ◽  
pp. 209-222 ◽  
Author(s):  
Hussain M. Rizk
Keyword(s):  
General Expression ◽  
Magnetic Surface ◽  
Anisotropic Pressure ◽  
Mean Velocity ◽  
Magnetohydrodynamic Equation ◽  
Toroidal Plasma ◽  
Hydrodynamic Calculations ◽  
The Mean ◽  
The One ◽  
Plasma Configuration

The relation between various surface quantities required in hydrodynamic calculations, and the relation between the parallel and perpendicular currents in an arbitrary magnetic toroidal plasma configuration with scalar pressure, are generalized to the case of anisotropic pressure. Magnetic co-ordinates for hydrodynamic equilibria in this configuration are defined. A general expression for the mean velocity of diffusion through a magnetic surface, on the basis of the one-fluid magnetohydrodynamic equation with anisotropic pressure, is derived.

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