Enhancement of Diffusion Due to Irradiation

1965 ◽  
Vol 20 (4) ◽  
pp. 527-532 ◽  
Author(s):  
W. Schule
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Production Rate ◽  
Point Defects ◽  
Aluminium Alloys ◽  
Annealed Specimen ◽  
Fast Neutrons ◽  
State Equilibrium

It is shown that in α-copper-aluminium alloys interstitials are able to change sites with the copper and aluminium atoms by diffusion. The activation energy for migration of interstitials could be determined to be 0.82 eV. In a well annealed specimen the interstitials and vacancies annihilate nearly exclusively by pair recombination. The production rate of free interstitials is found to be slightly larger than that of free vacancies during an irradiation with fast neutrons. The excess interstitials, which are supposed to originate from depleted zones, form clusters acting as sinks, at which essentially interstitials anneal out. Due to these sinks another steady state equilibrium („fixed vacancy case“) among point defects and sinks is achieved by repeated irradiations.

Evidence for a nuclear passage of nascent polypeptide-associated complex subunits in yeast

2001 ◽  
Vol 114 (14) ◽  
pp. 2641-2648
Author(s):  
Jacqueline Franke ◽  
Barbara Reimann ◽  
Enno Hartmann ◽  
Matthias Köhler ◽  
Brigitte Wiedmann
Keyword(s):  
Transcriptional Regulation ◽  
Steady State ◽  
Fluorescence Microscopy ◽  
Nuclear Import ◽  
Cell Fractionation ◽  
Active Process ◽  
Ribosomal Subunits ◽  
State Equilibrium ◽  
Nascent Polypeptide ◽  
Ribosome Binding

The nascent polypeptide-associated complex (NAC) has been found quantitatively associated with ribosomes in the cytosol by means of cell fractionation or fluorescence microscopy. There have been reports, however, that single NAC subunits may be involved in transcriptional regulation. We reasoned that the cytosolic location might only reflect a steady state equilibrium and therefore investigated the yeast NAC proteins for their ability to enter the nucleus. We found that single subunits of yeast NAC can indeed be transported into the nucleus and that this transport is an active process depending on different nuclear import factors. Translocation into the nucleus was only observed when binding to ribosomes was inhibited. We identified a domain of the ribosome-binding NAC subunit essential for nuclear import via the importin Kap123p/Pse1p-dependent import route. We hypothesize that newly translated NAC proteins travel into the nucleus to bind stoichiometrically to ribosomal subunits and then leave the nucleus together with these subunits to concentrate in the cytosol.

scholarly journals THE RICH AND THE POOR IN A SIMPLE MODEL OF GROWTH AND DISTRIBUTION

2016 ◽  
Vol 20 (7) ◽  
pp. 1934-1952 ◽  
Author(s):  
Kirill Borissov
Keyword(s):  
Economic Growth ◽  
Steady State ◽  
Simple Model ◽  
Disposable Income ◽  
State Equilibrium ◽  
Positional Concerns ◽  
The Poor ◽  
The Rich ◽  
Intertemporal Equilibrium ◽  
Unique Steady State

We consider a model of economic growth with altruistic agents who care about their consumption and the disposable income of their offspring. The agents' consumption and the offspring's disposable income are subject to positional concerns. We show that, if the measure of consumption-related positional concerns is sufficiently low and/or the measure of offspring-related positional concerns is sufficiently high, then there is a unique steady-state equilibrium, which is characterized by perfect income and wealth equality, and all intertemporal equilibira converge to it. Otherwise, in steady-state equilibria, the population splits into two classes, the rich and the poor; under this scenario, in any intertemporal equilibrium, all capital is eventually owned by the households that were the wealthiest from the outset and all other households become poor.

Rock Stresses Induced by Flow of Fluids into Boreholes

1963 ◽  
Vol 3 (01) ◽  
pp. 85-94 ◽  
Author(s):  
P.R. Paslay ◽  
J.B. Cheatham
Keyword(s):  
Steady State ◽  
Pressure Gradient ◽  
Production Rate ◽  
Flow Rate ◽  
Rate Increase ◽  
Rock Material ◽  
Inside Surface ◽  
Axial Position ◽  
Air Drilling ◽  
Intermediate Surface

Abstract Rock stresses and steady-state flow rates induced by the pressure gradient associated with the flow of formation fluid into a borehole have been analytically determined for a permeable, elastic material saturated with an incompressible fluid. In this analysis, the material properties and loading are considered to he symmetric about the axis of the borehole and independent of axial position. For Case I the material is assumed to have uniform permeability in the radial direction, whereas for Case II the permeability is assumed to have been reduced in a localized region adjacent to the hole by either normal well completion and production operations or deliberate plugging during air drilling.Results of a numerical example indicate that, in the absence of plugging, the rock shear strength must be approximately two-thirds the formation fluid pressure in order to prevent rock failure. The required rock strength is high for small radial zones of plugging and decreases as the region of reduced permeability becomes larger; however, a depth of plugging can be reached beyond which there is no real gain in strength, although the flow rate can be further reduced. Introduction During normal production of oil from a well, it is often desirable to increase the production rate of the formation fluid by increasing the pressure gradient through the formation adjacent to the borehole. Depending upon the magnitude of this pressure gradient and strength of the rock material, this production-rate increase can cause sloughing of the hole wall. In many cases, the production-rate increase can result in excessive sand production, increased wear of production equipment, lost production time and expensive workover jobs.In addition, the phenomenon of increased rock bit penetration rate with the use of a gaseous instead of a liquid drilling fluid has been observed in oilfield drilling operations and experimentally demonstrated by various investigators for several years. The improvement obtained by employing this technique can be quite significant and offers a promising method for reducing drilling costs. However, air drilling is currently limited to geographical locations where high-capacity water-bearing formations are not encountered. This limitation has prevented widespread adoption of air-drilling techniques, because the water influx into the borehole interferes with efficient removal of the drilling cuttings and usually results in a condition such that the bit becomes "balled-up" or stuck in the hole.In an attempt to remove the water-intrusion limitation from air drilling, various chemical and mechanical water shut-off methods have been proposed. Goodwin and Teplitz suggested one such proposal whereby the permeability of the water - bearing rock structure was reduced in the vicinity of the borehole. Although the development of a shut-off method based upon this approach would certainly be welcomed by the oil industry, it is conceivable that, under certain conditions of the pressure gradient, strength of the rock material and depth of the modified permeability zone, a stress field can be created that will result in an unstable hole.As part of their study, an analytical solution is given for stresses in an idealized model of a hole and the surrounding rock material. The purpose of the present study is to extend the analysis of Goodwin and Teplitz to gain more insight into the details and consequences of excessive production rates and formation water shut-off. In particular, simplified models of these problems have been analytically examined, which makes possible the evaluation of the type of stress fields that can be anticipated as a result of these production and drilling practices.Both problems solved concern the determination of the steady-state volume flow rate of the formation fluid and the resulting steady-state stress and displacement distribution in a hollow, cylindrical configuration. The cylinder of Case I, corresponding to the production-rate problem, consists of a material with a constant permeability from the inside surface to the outside surface; the cylinder of Case II, corresponding to the water shut-off problem, consists of a material with a constant permeability from the inside surface to an intermediate concentric cylindrical surface and a second constant permeability from the intermediate surface to the outside surface. SPEJ P. 85^

Predictive Kinetics-based Model for Shock-activated Reaction Synthesis of Ti3SiC2

2005 ◽  
Vol 20 (6) ◽  
pp. 1476-1484
Author(s):  
Jennifer L. Jordan ◽  
John A. Pelesko ◽  
Naresh N. Thadhani
Keyword(s):  
Heat Treatment ◽  
Activation Energy ◽  
Steady State ◽  
Predictive Model ◽  
Heat Dissipation ◽  
Experimental Results ◽  
Reaction Synthesis ◽  
Synthesis Conditions ◽  
Type Reaction ◽  
Activated State

A kinetics model based on mass and heat transport has been developed for Ti3SiC2 formation via shock-activated reaction synthesis of powder precursors. The model allows prediction of heat treatment conditions under which an otherwise steady-state reaction is taken over by a “run-away” combustion-type reaction during post-shock reaction synthesis of Ti3SiC2. Shock compression of Ti, SiC, and graphite precursors generates a densely packed highly activated state of reactants, which lowers the activation energy and results in an increased rate of formation of Ti3SiC2 at a lower temperature and in shorter times. The predictive model correlated with experimental results of fraction reacted as a function of time at heat-treatment temperatures of 1400 and 1600 °C illustrates an increased rate of reaction due to lowering activation energy, which also results in the reaction at 1600 °C being taken over by a “run-away” combustion-type reaction, as the rate of heat release due to reaction exceeds the rate of heat dissipation through the compact. Correlation of the model with experimental results illustrates that the predictive model can be used to optimize reaction synthesis conditions in shock-densified compacts of Ti3SiC2-forming powder precursors, to better understand the processes leading to a steady-state reaction being taken over by the combustion mode.

scholarly journals Comparison of Infant Test-Weighing and Hourly Breast Expression in Measuring Maternal Milk Production (P11-041-19)

2019 ◽  
Vol 3 (Supplement_1) ◽  
Author(s):  
Dayna Roznowski ◽  
Erin Wagner ◽  
Sarah Riddle ◽  
Laurie Nommsen-Rivers
Keyword(s):  
Steady State ◽  
Production Rate ◽  
Milk Production ◽  
Production Capacity ◽  
Limits Of Agreement ◽  
Term Infants ◽  
Maternal Milk ◽  
Milk Output ◽  
Before And After ◽  
The Difference

Abstract Objectives Measuring maternal milk production is cumbersome. Our objectives were to: 1) confirm that milk production rate reaches steady state at hour 2 of hourly breast emptying; and 2) compare agreement in milk production when measured using the well-established test-weighing method versus the more efficient hourly breast emptying method (Lai, et al., Breastfeeding Medicine, 2010). Methods Eligible mothers were 4–10 weeks postpartum and exclusively breastfeeding their healthy, singleton, term infants. A subset of mothers test-weighed (TW) their infant (± 2 g) before and after breastfeeding for 48h. Within 1 week of TW, mothers had a morning visit at the research clinic for hourly breast expression measurements. Mothers emptied both breasts at baseline (h0), and 1, 2, and 3 hours after baseline (h1, h2, h3) using a hospital-grade pump. We recorded hourly milk output ± 1 g and adjusted production rate (g/h) to exact interval (minutes from end of previous to end of current expression). We used paired t-test to compare g/h at h3 versus h0, h1, and h2. We estimated mother's steady-state milk production rate (MPR, g/h) as mean (h2, h3). We used the Bland-Altman method for determining the 95% limits of agreement in measuring milk production (g/24h) using TW versus MPRx24. Results 23 mothers (65% primiparous) were 54 ± 14 days postpartum. Milk output was 185 ± 55 g at h0 and 60 ± 26, 47 ± 13, 44 ± 13 g/h at h1, h2, and h3, respectively. Mean paired difference (vs. h3) was significant at h0 and h1 (P < 0.05), but not at h2 (P > 0.05, h3 - h2 = 3 ± 10 g/h). In the subset with TW data (n = 16), mean TW milk output was 717 ± 119 g/24h, and mean MPRx24 was 1085 ± 300 g/24h. Mean difference, MPRx24 - TW [± 95% limits of agreement], was 368 [± 468] g/24h; and mean ratio, MPRx24/TW, was 1.5 [± 0.4]. Both difference and ratio significantly increased as MPR increased (P < 0.05). Conclusions Hourly milk production reaches steady state at h2; thus, mean (h2, h3) is a valid measure of current maternal milk production capacity. However, there was not homogeneous agreement between MPR and TW, and the 95% limits of agreement were very wide: -91 to 459 g/24h when expressed as the difference, and 0.9 to 1.9-fold as a ratio. Thus, MPR is feasible for researching variation in maternal milk production but not for researching variation in infant intake. Funding Sources None. Supporting Tables, Images and/or Graphs

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