Fluctuations of Perceptual Organization and Orientation: Stochastic (Random) or Steady State (Satiation)?

1970 ◽  
Vol 31 (3) ◽  
pp. 739-749 ◽  
Author(s):  
Timothy G. Sadler ◽  
Roy B. Mefferd
Keyword(s):  
Steady State ◽  
Perceptual Organization ◽  
Fluctuation Phenomena ◽  
Published Data ◽  
Apparent Depth ◽  
Duration Data ◽  
Lateral Organization

Using flat drawings, intra-reversal times were obtained for two kinds of fluctuations, perspective reversals in a figure eliciting apparent depth and reversals of lateral organization in a figure not eliciting apparent depth. The durations of the alternate percepts (P1 and P2) between reversals early in a viewing session were compared with recently published data of the same type. In the latter study, P1 was found to be of longer duration than P2, both with a flat drawing and a rotating skeletal cube. These prior data were explained in terms of satiation theory; however, we found no significant differences between P1 and P2 with two different groups of Os and with two figures. Explanations for these differences in results were advanced. The use of grouped percept-duration data to support steady state (e.g., satiation) theories of perceptual fluctuation phenomena was criticized.

Perception of Depth in Rotating Objects: 4. Fluctuating Stereokinetic Perceptual Variants

1968 ◽  
Vol 27 (1) ◽  
pp. 255-276 ◽  
Author(s):  
Roy B. Mefferd
Keyword(s):  
Steady State ◽  
Perceptual Organization ◽  
Phase 1 ◽  
Apparent Depth ◽  
Phase 2 ◽  
Basic System ◽  
Axis Of Rotation ◽  
Visual Systems ◽  
Processing Information ◽  
The One

There are a variety of stereokinetic percepts that fluctuate suddenly and unpredictably. On first viewing their sequence is predictable (Phase 1), but later it becomes unpredictable (Phase 2). A given percept results from the interplay of three independent visual systems: (1) the near-far mechanism (perspective reversals), (2) the one object-multiple object mechanism (degree of perceptual organization), and (3) the anchor point mechanism (apparent location of the axis of rotation). It was hypothesized that these fluctuating phenomena result from the operation of a basic system for repetitively sampling and pre-processing information on orientation, perceptual organization, and location of the axis of rotation and that a steady-state apparent-depth mechanism stabilizes the systems.

Antimalarial Drugs, Pregnancy and Lactation

Lupus ◽  
1993 ◽  
Vol 2 (1_suppl) ◽  
pp. 21-23 ◽  
Author(s):  
Ann L. Parke
Keyword(s):  
Steady State ◽  
Breast Milk ◽  
Disease Activity ◽  
Fetal Loss ◽  
Antimalarial Drugs ◽  
Published Data ◽  
Antimalarial Therapy ◽  
Pregnancy And Lactation ◽  
Major Factors ◽  
Normal Offspring

Disease activity has been demonstrated to be one of the major factors contributing to fetal loss in SLE patients, and discontinuation of antimalarial therapy can precipitate a flare of disease. It is therefore important to determine whether it is safe to continue antimalarial therapy throughout pregnancy. We have previously stated that we consider lupus patients and their fetuses to be at risk for disaster if antimalarial therapy is discontinued during pregnancy, and it has been our experience that lupus patients can produce normal offspring even if they are taking daily chloroquine or hydroxychloroquine. Several other reports now support our findings that it is probably safe to continue antimalarial therapy during pregnancy, although there are no large studies published. Data on the secretion of hydroxychloroquine in the breast milk of patients on steady-state hydroxychloroquine therapy are minimal, and further studies are required to determine whether these women can safely nurse their infants while taking hydroxychloroquine daily.

scholarly journals Computer simulations of propofol infusions for total intravenous anaesthesia in dogs : review article

2009 ◽  
Vol 80 (1) ◽  
Author(s):  
K.E. Joubert
Keyword(s):  
Steady State ◽  
Plasma Concentration ◽  
Simulated Data ◽  
The Body ◽  
Published Data ◽  
Total Intravenous Anaesthesia ◽  
International Treaties ◽  
Duration Of Action ◽  
Intravenous Anaesthesia ◽  
Anaesthetic Depth

The volatile anaesthetic agents halothane, isoflurane and enflurane are all chlorofluorocarbons and according to international treaties, their emission into the atmosphere will be prohibited from the year 2030. The agents desflurane and sevoflurane are fluorinated hydrocarbons and act as greenhouse gases. The future of veterinary anaesthesia could be dependent on the development of total intravenous anaesthesia. Drugs utilised in total intravenous anaesthesia (TIVA) should have a short duration of action and no tendency to accumulate in the body. Propofol has been the dominant agent used. Computer technology has enabled targeted plasma concentration controlled infusions to replace manual infusion regimens. This study simulated the pharmacokinetics of various infusion regimens similar to those used in clinical practice using previously published pharmocokinetic data. Bolus doses of 0, 4, 6 and 8 mg/kg were simulated in combination with infusion rates of 0, 0.2, 0.3 and 0.4 mg/kg/min for either 240 or 1440 min. The computer was also programmed to maintain a steady state plasma concentration based on the previous simulated data. Generated data were then compared with published data. Changes in the context-sensitive half-life for propofol were also evaluated. Results showed that the generated data were similar to published data. A decrease in plasma concentration to levels associated with a light plane of anaesthesia was evident even when the highest bolus dose and infusion rate were used. There was a slow rise in plasma concentration when only an infusion was used. A lightening of anaesthetic plane may be evident early in the course of TIVA and careful monitoring of anaesthetic depth is required. As the duration of the infusion increased, plasma concentration steadily rose but achieved 95 % of the steady state by 204 min. The most dramatic changes in plasma concentration occurred in the first hour of an infusion. Similarly, the infusion rates decreased most in the first 70 min. Most changes in anaesthetic depth are likely to occur early in the course of TIVA and careful observation of anaesthetic depth is required.

scholarly journals Na/K pump current in aggregates of cultured chick cardiac myocytes.

1990 ◽  
Vol 95 (1) ◽  
pp. 61-76 ◽  
Author(s):  
J R Stimers ◽  
N Shigeto ◽  
M Lieberman
Keyword(s):  
Steady State ◽  
Cardiac Myocytes ◽  
Pump Current ◽  
Cardiac Cells ◽  
Hill Coefficient ◽  
Published Data ◽  
Free Solution ◽  
Embryonic Chick ◽  
Current Voltage ◽  
Current Voltage Relationship

Spontaneously beating aggregates of cultured embryonic chick cardiac myocytes, maintained at 37 degrees C, were voltage clamped using a single microelectrode switching clamp to measure the current generated by the Na/K pump (Ip). In resting, steady-state preparations an ouabain-sensitive current of 0.46 +/- 0.03 microA/cm2 (n = 22) was identified. This current was not affected by 1 mM Ba, which was used to reduce inward rectifier current (IK1) and linearize the current-voltage relationship. When K-free solution was used to block Ip, subsequent addition of Ko reactivated the Na/K pump, generating an outward reactivation current that was also ouabain sensitive. The reactivation current magnitude was a saturating function of Ko with a Hill coefficient of 1.7 and K0.5 of 1.9 mM in the presence of 144 mM Nao. The reactivation current was increased in magnitude when Nai was increased by lengthening the period of time that the preparation was exposed to K-free solution prior to reactivation. When Nai was raised by 3 microM monensin, steady-state Ip was increased more than threefold above the resting value to 1.74 +/- 0.09 microA/cm2 (n = 11). From these measurements and other published data we calculate that in a resting myocyte: (a) the steady-state Ip should hyperpolarize the membrane by 6.5 mV, (b) the turnover rate of the Na/K pump is 29 s-1, and (c) the Na influx is 14.3 pmol/cm2.s. We conclude that in cultured embryonic chick cardiac myocytes, the Na/K pump generates a measurable current which, under certain conditions, can be isolated from other membrane currents and has properties similar to those reported for adult cardiac cells.

Stoichiometric model of chlorine dioxide delignification of hardwood kraft pulps with oxidant-reinforced extraction effect,

TAPPI Journal ◽  
2013 ◽  
Vol 12 (2) ◽  
pp. 17-26 ◽  
Author(s):  
BRIAN N. BROGDON
Keyword(s):  
Steady State ◽  
Chlorine Dioxide ◽  
Empirical Relationship ◽  
Kappa Number ◽  
Published Data ◽  
Kraft Pulps ◽  
Mathematical Transformation ◽  
Stoichiometric Model ◽  
Hardwood Species ◽  
Steady State Model

A generalized, steady-state model for hardwoods is proposed for predicting bleaching delignification and/or chlorine dioxide (ClO2) consumption for sequences that use oxidant-reinforced extraction. Published data for various hardwood species and mixtures were analyzed to develop the model. The kappa number data from these studies were normalized to their respective pre-D0 kappa number, and the normalized kappa numbers were plotted against the bleach demand. This mathematical transformation allowed for various brownstocks and oxygen-delignified pulps with different kappa numbers to be modeled as a single curve based on an empirical relationship with fitted equation parameters. One of the two equation parameters could be expressed as simple functions of oxidant-reinforced extraction conditions (i.e., peroxide dosage). The model forecasts ClO2 usage reasonably well (±0.20% ClO2 on pulp) for conventional ClO2 delignification with extraction. Attempts to incorporate modified bleaching delignification processes that eliminate hexenuronic acids into the model were unsuccessful; data were insufficient to develop a relationship. This straightforward stoichiometric model contains relatively few fitted parameters to be determined. The model could be used with other steady-state brightening-stage models to predict bleach usage.

A MATHEMATICAL MODEL FOR TRAINING IMPULSE AND LACTATE INFLUX AND OUTFLUX DURING EXERCISE

2009 ◽  
Vol 20 (01) ◽  
pp. 147-177 ◽  
Author(s):  
JOHN F. MOXNES ◽  
KJELL HAUSKEN
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Lactate Concentration ◽  
Lactate Production ◽  
Published Data ◽  
Interval Exercise ◽  
Common Concept ◽  
Training Impulse ◽  
The Mathematical Model ◽  
Upper Boundary

This paper provides a mathematical description based on the theory of differential equations, for the dynamics of lactate production and removal. Analytical and numerical results for training/exercise of endurance of athletes are presented based on the common concept of training impulse (Trimp). The relationships between activity, production rate, and removal strategies of lactate are studied. Parameters are estimated from published data. A model for optimum removal of lactate after exercise is developed. The model provides realistic predictions when compared with experimental results. We show some specific examples for the usefulness of the mathematical model by studying some recent problems discussed in the literature. (a) Is interval exercise more beneficial than steady-state exercise? (b) What is the optimum aerobic power during recovery? We discuss whether steady-state exercise gives higher Trimp than interval exercise, when imposing an upper boundary for the lactate concentration as a constraint. The model allows for testing all imaginable kinds of steady-state and interval exercises in search of the optimal exercise regime for individuals with various kinds of characteristics. In general, the dynamic model constitute a powerful tool describing the processes by which the concentration of lactate can be studied and controlled to decrease fatigue and increase endurance.

scholarly journals Complete Spatial Mapping of Steady-State and Stress Erythropoiesis

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 7-7
Author(s):  
Qingqing Wu ◽  
Jizhou Zhang ◽  
Courtney Johnson ◽  
Anastasiya Slaughter ◽  
Margot Lindsay May ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Steady State ◽  
Single Cells ◽  
Differentially Expressed ◽  
Published Data ◽  
Erythroid Progenitors ◽  
Erythroid Progenitor ◽  
Clonal Architecture ◽  
Stress Erythropoiesis

The anatomy of differentiation in the bone marrow (BM) is poorly understood due to lack of markers to image stepwise HSPC differentiation. We analyzed 250+ cell surface molecules in all hematopoietic progenitors and identified 56 differentially expressed markers in at least one HSPC that can be "mixed and matched" to prospectively image any HSPC of interest in the bone marrow. We used this data to develop a pipeline to map stepwise erythropoiesis in vivo. We found that all erythroid progenitors can be defined as Ly6C-CD27-ESAM-CD117+ cells and then Pre-MegE (earliest erythroid progenitor Cell Stem Cell. 2007 1(4):428-42) are CD150+CD71-. These give rise to CD71+CD150+ Pre-CFU-E that differentiate into CD71+CD150- CFU-E that then generate early erythroblasts. All BFU-E activity was restricted to Pre-MegE and Pre- CFU-E (70 and 30% of all BFU-E) whereas all CFU-E colonies were spread between Pre-MegE (44%), pre-CFU-E (10%) and CFU-E (46%). We also confirmed previously published data showing that CD71 and Ter119 can be used to image stepwise terminal erythropoiesis; CD71+Ter119dim early erythroblasts, CD71+Ter119bright late erythroblasts, CD71dimTer119bright reticulocytes and CD71-Ter119bright erythrocytes. Importantly, all populations were detected at identical frequencies using FACS or confocal imaging indicating that our imaging strategy detects all erythroid cells (Pre-CFU-E: 0.022 vs 0.027 %; CFUE: 0.32 vs 0.30%; Early-Ery: 0.62 vs 0.66%; Late-Ery: 32.05 vs 32.12%; Reticulocyte: 5.98 vs. 3.36%; Erythrocytes: 12.49 vs. 13.47%). We mapped the 3D location of every erythroid lineage cell in mouse sternum and interrogated the spatial relationships between the different maturation steps and with candidate niches. We compared the interactions found in vivo with those found in random simulations. Specifically, we used CD45 and Ter119 to obtain the spatial coordinates of every hematopoietic cell. Then we randomly placed each type of erythroid lineage cell at identical frequencies as those found in vivo to generate random simulations. We found erythroid progenitors show no specific association with HSC, indicating that Pre-Meg-E or more primitive progenitors leave the HSC niche after differentiation. Both Pre-Meg-E and Pre-CFU-E are found as single cells through the central BM space and do not specifically associate with other progenitors, or components of the microenvironment. In contrast almost all CFU-E locate to strings (28 strings per sternum) containing 8 CFU-E that are selectively recruited to sinusoids (mean CFU-E to sinusoid distance=2.2µm). As soon as CFU-E detach from sinusoids they downregulate CD117 and upregulate CD71 giving rise to a cluster of early erythroblasts that buds from the vessel. These progressively upregulate Ter119 to generate large clusters of late erythroblasts that in turn differentiate into clusters of reticulocytes and erythrocytes. To examine the clonal architecture of erythropoiesis we used Ubc-creERT2:confetti mice where a tamoxifen pulse leads to irreversible expression of GFP, CFP, YFP or RFP. Four weeks later we found that the CFU-E strings are oligoclonal with each clone contributing 2-6 CFU-E to the string. The budding erythroblasts clusters are similarly organized. These indicate that different CFU-E are serially recruited to the same sinusoidal spot where they self-renew 1-2 times and then undergo terminal differentiation. We then tracked how this architecture changed in response to stress (hemorrhage). Two days after bleeding we found that Pre-Meg-E and Pre-CFU-E numbers and locations were unaltered. The number of CFU-E strings remained constant (30 CFUE strings/sternum) but all strings contained more CFU-E (2-fold) suggesting increased self-renewal. Unexpectedly, fate mapping showed that the size of CFU-E clones did not increase when compared to steady-state. These results indicate that all CFU-E expand in respond to stress and that this is mediated via increased recruitment and differentiation of upstream progenitors. In summary we have found 56 differentially expressed markers that can be combined to detect most HSPC; validated a 5-color stain to image and fate map all steps of red blood cell maturation in situ; demonstrated that terminal erythropoiesis emerges from strings of sinusoidal CFU-E, and revealed the clonal architecture of normal and stress erythropoiesis. Disclosures No relevant conflicts of interest to declare.

scholarly journals Modified-atmosphere Packaging of Blueberry Fruit: Modeling Respiration and Package Oxygen Partial Pressures as a Function of Temperature

1994 ◽  
Vol 119 (3) ◽  
pp. 534-539 ◽  
Author(s):  
Arthur C. Cameron ◽  
Randolph M. Beaudry ◽  
Nigel H. Banks ◽  
Mark V. Yelanich
Keyword(s):  
Activation Energy ◽  
Mathematical Model ◽  
Steady State ◽  
Modified Atmosphere Packaging ◽  
Vaccinium Corymbosum ◽  
Published Data ◽  
Modified Atmosphere ◽  
Highbush Blueberry ◽  
Partial Pressures ◽  
Low Levels

A mathematical model was developed to characterize the interaction of fruit O2 uptake, steady-state O2 partial pressures in modified-atmosphere (MA) packages ([O2]pkg), and film permeability to O2 (Po2) from previously published data for highbush blueberry (Vaccinium corymbosum L. `Bluecrop') fruit held between 0 and 25C. O2 uptake in nonlimiting O2 (Ro2max,T) and the [O2]pkg at which O2 uptake was half-maximal (K½T) were both exponentially related to temperature. The activation energy of 02 uptake was less at lower [O2]pkg and temperature. The predicted activation energy for permeation of O2 through the film (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{E}_{\mathrm{a}}^{\mathrm{P_{\mathrm{o}_{2}}}}\) \end{document} kJ·mol-1) required to maintain close-to-optimum [O2]pkg across the range of temperatures between 0 and 25C was ≈ 60 kJ·mol-1. Packages in which diffusion was mediated through polypropylene or polyethylene would have values \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{E}_{\mathrm{a}}^{\mathrm{P_{\mathrm{o}_{2}}}}\) \end{document} of ≈ 50 and 40 kJ·mol-1, respectively, and would have correspondingly greater tendencies for [O2]pkg to decrease to excessively low levels with an increase in temperature. Packages that depend on pores for permeation would have an \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{E}_{\mathrm{a}}^{\mathrm{P_{\mathrm{o}_{2}}}}\) \end{document} of <5 kJ·mol-1. Our procedure predicted that, if allowed to attain steady-state conditions, packages with pores and optimized to 2 kPa O2 at 0C would become anaerobic with as little as a 5C increase in temperature. The results are discussed in relation to the risk of temperature abuse during handling and marketing of MA packaged fruit and strategies to avoid induction of anaerobiosis.

scholarly journals On equivalent granular void ratio and steady state behaviour of loose sand with fines

2008 ◽  
Vol 45 (10) ◽  
pp. 1439-1456 ◽  
Author(s):  
M. M. Rahman ◽  
S. R. Lo ◽  
C. T. Gnanendran
Keyword(s):  
Steady State ◽  
Void Ratio ◽  
Soil Mechanics ◽  
Back Analysis ◽  
B Value ◽  
Published Data ◽  
Factors Affecting ◽  
State Variable ◽  
Cyclic Resistance ◽  
Alternative State

Void ratio has traditionally been used as a state variable for predicting the liquefaction behaviour of soils under the critical state soil mechanics framework. Recent publications show that void ratio may not be a good state variable for characterizing sand with fines. An alternative state variable referred to as the equivalent granular void ratio has been proposed to resolve this problem. To calculate this alternative state variable, a b parameter is needed. This b parameter represents the fraction of fines that actively participate in the force structure of the solid skeleton. However, predicting the value of b is problematic. Most, if not all, of the b values reported were determined by case-specific back-analysis, that is, the b value was selected so that a single correlation between equivalent granular void ratio and the measured steady state strength (or cyclic resistance) could be achieved. This paper examines the factors affecting the b value based on published work on binary packing. This leads to a simple semi-empirical equation for predicting the value of b based on fines size and fines content. Published data appear to be in support of the proposed equation. A series of experiments were conducted on a specially designed sand–fines type to provide additional validation of the proposed equation and to reinforce the use of equivalent granular void ratio in a more generalized context.

Mathematical model of fetal circulation and oxygen delivery

1985 ◽  
Vol 249 (2) ◽  
pp. R192-R202 ◽  
Author(s):  
F. J. Huikeshoven ◽  
I. D. Hope ◽  
G. G. Power ◽  
R. D. Gilbert ◽  
L. D. Longo
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Oxygen Tension ◽  
Oxygen Delivery ◽  
Vascular System ◽  
Arterial Oxygen Tension ◽  
Ascending Aorta ◽  
Arterial Oxygen ◽  
Published Data ◽  
Fetal Circulation

To better understand the fetal circulation and its regulation we constructed a dynamic model of fetal circulation as a transport system. The fetal vascular system is divided into 16 compartments which incorporate the peculiarities of the fetal circulation that produce a difference in oxygen concentration in blood supplying the upper and lower body. Recently published data is used to provide a firm experimental base for the model. The model is used to examine how the results on parts of the fetal cardiovascular system and fetal oxygen consumption are compatible and form a coherent description. We also studied the effects of disturbances from the normal steady state produced by changes in patterns of and resistances to blood flow. A maternal placental blood flow of less than 200 ml X min-1 X kg fetal wt-1 produces a steady-state value of oxygen tension in the fetal ascending aorta of less than 17 mmHg, which is incompatible with normal oxygen delivery. A minimal value of umbilical flow providing an adequate oxygen supply to the fetal body is 87 ml X min-1 X kg fetal wt-1. Due to the geometry of the fetal circulation, the highest normal oxygen tension in the fetal ascending aorta is approximately 25 mmHg, only 8 mmHg above the lowest normal tension of 17 mmHg. Dynamic studies using the model demonstrate differences in response of fetal arterial oxygen tension to temporal cord occlusion and temporal decrease in maternal placental flow.

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