Plateau Period Research Articles

Effects of the hormone therapy, drospirenone and 17-beta estradiol, on early morning blood pressure in postmenopausal women with hypertension

Drospirenone (DRSP), is a unique progestin with antimineralocorticoid activity that has been combined with 17-β estradiol (E2) for the treatment of symptoms of the menopause in women with hypertension. We assessed the effects of DRSP/E2, E2 alone, and placebo on early morning systolic blood pressure (BP) as well as the rate of rise in systolic BP in 748 postmenopausal women with stage 1 and 2 hypertension at baseline and after 8 weeks of double-blind therapy. Patient characteristics (mean age, 56.5 years, 73% to 77% Caucasian; 13% to 17% African-American) and the clinic (152/95 mm Hg) and 24-hour BP (139/83 mm Hg) measurements were similar at baseline. The early morning systolic BP was reduced significantly on DRSP at 3 mg, 2 mg, and 1 mg with E2 compared with placebo, while E2 alone was similar to placebo. The reductions in early morning systolic BP were larger with increasing dose. Changes in the rate of rise in systolic BP between the lowest values during sleep and following a plateau period post-awakening was significant for the 3 mg DRSP group. In conclusion, DRSP/E2 induced significant reductions in early morning systolic BP in post-menopausal women. This attribute could play a potential role in reducing some of the untoward cardiac and cerebrovascular events that have been observed in studies of other progestins/estrogens in postmenopausal women.

Mechanical Dysfunction in Extreme QT Prolongation

Although cardiac mechanical dysfunction has not been reported in congenital long QT syndrome (LQTS), theoretically abnormal cardiac repolarization may confer a substrate for mechanical dysfunction via calcium overload during the prolonged plateau period. We report the first clinical descriptions of a patient who supports this hypothesis. Clinical, electrocardiographic, and echocardiographic evaluations were performed on a newborn presenting to Milwaukee Children's Hospital and subsequently referred to Mayo Clinic's LQTS Clinic. Mutational analysis of the 10 known LQTS-susceptibility genes was performed using denaturing high performance liquid chromatography and DNA sequencing. Presenting with fetal bradycardia from 2:1 atrioventricular block, a male Caucasian infant manifested extreme QT prolongation (QT interval corrected for heart rate: 800 milliseconds), 2:1 atrioventricular conduction, and macroscopic T-wave alternans after birth. At 6 weeks of age, the infant demonstrated 20 seconds of torsades de pointes. The family history was unremarkable, screening electrocardiograms of first-degree relatives revealed normal findings, and mutational analysis of all known LQTS-susceptibility genes was negative. Echocardiographically, the infant demonstrated globally abnormal systolic and diastolic dysfunction before the onset of arrhythmias. This infantile presentation of QT extremis and cardiac dysfunction provides support for the hypothesis of mechanical perturbations stemming from abnormal repolarization. Future studies are needed to investigate whether or not the typical patient with congenital LQTS exhibits any evidence for mechanical dysfunction.

Increasing Selenium Concentration in Milk: Effects of Amount of Selenium from Yeast and Cereal Grain Supplements

Two experiments were conducted to establish responses in milk Se concentrations in grazing dairy cows to different amounts of dietary Se yeast, and to determine the effects of the Se concentration of the basal diet. The hypothesis tested was that the response in milk, blood, and tissue Se concentrations to supplemental Se would not be affected by whether the Se was from the basal diet or from Se yeast. In addition, by conducting a similar experiment in either early (spring; experiment 1) or late (autumn; experiment 2) lactation, we hypothesized that different Se input-output relationships would result. Both 6-wk experiments involved 60 multiparous Holstein-Friesian cows, all of which had calved in spring. They were allocated to 1 of 10 dietary Se treatments that included 2 types of crushed triticale grain (low Se, approximately 165μ g of Se/kg of DM; or high Se, approximately 580μ g/kg of DM) fed at 4kg of DM/d, and 1kg of DM/d of pellets formulated to carry 5 quantities of Se yeast (0, 4, 8, 12, or 16mg of Se). Daily total Se intakes ranged from <2 to >18 mg/cow in both experiments. Milk Se concentrations plateaued after 15 and 7 d of supplementation in experiments 1 and 2, respectively, and then remained at plateau concentrations. Average milk Se concentrations for the plateau period increased as the amount of Se yeast increased, and low- and high-Se grain treatments were different at all quantities of Se yeast, although there was a tendency for this difference to diminish at the greatest concentrations of yeast. There were significant positive, linear relationships between Se intake and the concentrations of Se in milk, which were not affected by the source of Se, and the relationships were similar for both experiments. Therefore, the output of Se in milk in experiment 1 was greater than that in experiment 2 because the milk yield of the cows in early lactation was greater. The estimated proportions of Se partitioned to destinations other than milk and feces increased with the amount of Se in the diet and were greater in experiment 2 than in experiment 1, a result that was supported by Se concentrations in whole blood and plasma and in semitendinosus muscle tissue. If high-Se products are to be produced for human nutrition, it is important to be able to develop feeding systems that produce milk with consistent and predictable Se concentrations so that products can consistently meet specifications. The results indicate that this objective is achievable.

Muscle Strength Recovery in Treated Guillain-Barré Syndrome

To assess the recovery in muscle strength and functional capacities in subjects with Guillain-Barré syndrome (GBS) for 18 months after onset. Six GBS patients were treated and transferred to our rehabilitation center within the first week of recovery. Isometric and isokinetic strength increased significantly during the first 6 months (P < 0.01). Between 6 and 18 months, muscle strength increased less rapidly (P < 0.05). We showed a significant negative correlation between plateau period duration and knee extensors, elbow flexors muscles strength recovery (rho = -0.82; P = 0.05). At 6 months, manual muscle testing and functional independence motor total scores were close to normal levels. At 18 months, all patients satisfied the criteria for a full recovery. However, they felt difficulties after prolonged exercise. Until 18 months of recovery, dynamometric measures still showed significant strength improvement. This underscores the need for a minimal 24 months of clinical follow-up with an individualized rehabilitation management program.

Dynamic process of dendrite fragmentation in solidification from undercooled Si melt using time-resolved x-ray diffraction

The spontaneous dendrite fragmentation in solidification from undercooled Si melt was analyzed by time-resolved two-dimensional x-ray diffractometry. For the sample solidified at ΔT=261K, several spots appeared at 1ms after recalescence and the subsequent transition from spots to rings occurred within ∼25ms, which suggests that the fragmentation occurred after recalescence but just at the initial stage of the plateau period. Although the present experiment supported that the driving force for the fragmentation is a capillarity effect at the plateau period, the time scale for the fragmentation differed from the current quantitative prediction.

Decision Making With Uncertainty While Developing Multiple Gas/Condensate Reservoirs: Well Count and Pipeline Optimization

Summary Well-developed methodology exists for handling uncertainty for a single reservoir. However, development of multiple fields presents a significant challenge when uncertainty in a large number of variables, such as gas in place and liquid yield, occur in each reservoir. Some of the challenges stem from our need to forecast the system behavior involving a coupled reservoir/wellbore/surface (CRWS) network for the entire spectrum of variables so that facilities can be designed for the range of fluid composition and throughput. Of course, assessing well count and sequencing well drills are some of the important objectives. This paper describes probabilistic production forecasting with a compositional CRWS network model for nine reservoirs involved in delivering gas supply to a liquefied natural gas (LNG) plant in Nigeria. Our main objective was to use an economic indicator to select the optimal design of two main pipelines, each transporting 200 and 300 MMscf/D from the two production platforms, located 15 and 5 km, respectively, from the processing platform. Rate and cumulative profiles showed that sustained deliverability of gas could be realized for approximately 11 years before the decline occurred in high-permeability reservoirs. In other words, uncertainty in gas in place did not surface during the plateau period, only during the decline period lasting another 5 years after the first 11. In contrast, the liquid rates exhibited a large uncertainty band throughout, a direct manifestation of the condensate yield issue. The uncertainty band among each of the 12 components aided facilities design. Differences in net present value (NPV) and discounted profitability index (DPI) were used as discriminators for discerning optimal pipe size from the standpoint of project economics.

Secular Trends in Childhood Obesity in Denmark During 50 Years in Relation to Economic Growth

Our aim was to examine whether secular trends in childhood overweight and obesity during five decades could be explained by economic growth. Annual measurements of height and weight were available for all children born between 1930 and 1983 attending primary school in the Copenhagen Municipality: 165,389 boys and 163,609 girls from the age of 7 through 13 years. After computerization, we calculated BMI (kg/m2) and estimated the prevalence of overweight and obesity, according to international age- and gender-specific criteria, by year of birth and of measurement, and separately by each age group and gender. Economic growth was indicated by the Gross National Product and the overall consumption per capita, adjusted for inflation. The prevalence of overweight occurred in phases: an increase from 1930 until the 1950s, followed by a plateau period between the 1950s and the 1960s and a steep increase thereafter. This pattern was apparent across all age groups and in both genders. Obesity trends showed a similar phase pattern; the prevalence remained relatively stable from 1930 until the 1940s, increased until the mid-1950s, followed by a plateau until 1965, and thereafter a second steep increase. Obesity trends were similar among boys across all age groups, although only among girls from 11 to 13 years of age. In both genders, increments were most pronounced in the upper BMI percentiles. After stagnation until 1947, the economic growth indicators showed a steady increase; i.e., after the first increase started in overweight and obesity, whether analyzed by year of birth or year of measurement, there were no indications of phases in the rise thereafter. Prevalence of overweight and obesity among Danish children rose in phases, which were not paralleled by trends in economic growth. The macroeconomic growth indicators seem inappropriate as proxies for the environmental exposures that have elicited the obesity epidemic.

Infection Dynamics of Centrocestus armatus Cercariae (Digenea: Heterophyidae) to Second Intermediate Fish Hosts

The infection dynamics of Centrocestus armatus cercariae with respect to second intermediate fish hosts were investigated using cercariae collected from naturally infected Semisulcospira libertina. Cercariae survival and infectivity were recorded at 2-hr intervals. Survival remained constant but decreased abruptly at 30 hr of age. An age-dependent model presented the best-fit curve for the survival data (r2 0.936), implying that cercariae tended to allocate resources equally among themselves and then died once those resources were depleted. Cercariae infectivity remained constant over the first 10 hr of life and then declined; an age-dependent model also provided a better fit (r2 = 0.956). The transmission rate of C. armatus cercariae to the fish host was relatively low near the time of emergence from the snail host but peaked at 85% after 1 hr and then maintained a plateau period until 5 hr of exposure to fish. The pattern of transmission was also investigated initially at varying densities of cercariae and then by maintaining a constant cercariae density but varying the total number. Results revealed that the pattern of transmission was frequency-dependent.

Topiramate effects on the EEG and alertness in healthy volunteers: A different profile of antiepileptic drug neurotoxicity

Objective Previous quantitative EEG (QEEG) studies of carbamazepine (CBZ), oxcarbazepine (OXC), and phenytoin (PHT) revealed a pattern of EEG slowing and an increase in drowsiness on the awake maintenance task (AMT). EEG slowing has been shown to correlate with negative effects on cognitive tests. Topiramate (TPM) is a novel AED with relatively large negative effects on cognitive function. We tested the hypothesis that TPM would induce significant slowing of EEG background rhythms and an increase in AMT drowsiness. Methods Forty healthy volunteers were randomized to TPM, gabapentin (GBP), or placebo. Doses were escalated as tolerated to a maximum of 400 mg/day for TPM or 3600 mg/day for GBP, over a 10-week period, followed by a minimum 2-week plateau period. Volunteers underwent an EEG, cognitive tests, and the AMT prior to starting an AED and again 12 weeks later. The EEG was captured using a structured recording protocol and quantified using the fast Fourier transform. Four target measures were derived from the averaged occipital electrodes (peak frequency of the dominant posterior rhythm, median frequency, percentage theta, and percentage delta). Test–retest changes for all measures were scored against similar test–retest distributions previously obtained from untreated healthy volunteers. Results TPM produced no significant change in any of the four target EEG measures or on the AMT, even though several target cognitive tests revealed moderate or greater negative effects. There were also no significant changes in the placebo group. GBP slowed the peak and median frequency EEG measures and increased the percentage of theta and delta activity. Neither TPM, GBP, nor placebo caused a significant increase in drowsiness on the AMT. Conclusions TPM has a unique neurotoxicity profile. It has no effect on EEG background measures or on the AMT, but induces moderate to large negative changes in many cognitive test scores. This profile differs from those of CBZ, OXC, PHT, and GBP.

実験計画法を用いた貯留層の不確実性評価

Systematic approaches to uncertainty analysis in undeveloped oil or gas fields are everlasting challenges in the oil industry. Probabilistic estimations of recoverable reserves, and plateau period are far from being simple because reservoir parameters often have so-called the interacting effects. Further difficulty stems from the fact that they need many flow-simulation runs before running the Monte Carlo simulations. Solutions to reduce the number of necessary simulation runs without losing the accuracy of estimation have been studied.In this decade, experimental design (ED) approach is focused on instead of the conventional one-factor-at-a-time (OFAAT) method. One of the advantages of ED is that much less flow-simulation runs are needed to obtain relatively unbiased probabilistic estimates, while the OFAAT method needs more flow simulation runs, and tends to yield a narrow range of probabilistic distribution.This report reviews the ED approach in the oil industry and the results of application to our field development case.

Lipoprotein lipase in hemodialysis patients: indications that low molecular weight heparin depletes functional stores, despite low plasma levels of the enzyme

BackgroundLipoprotein lipase (LPL) has a central role in the catabolism of triglyceride-rich lipoproteins. The enzyme is anchored to the vascular endothelium through interaction with heparan sulphate proteoglycans and is displaced from this interaction by heparin. When heparin is infused, there is a peak of LPL activity accompanied by a reduction in triglycerides (TG) during the first hour, followed by a decrease in LPL activity to a stable plateau during the remaining session while TG increase towards and beyond baseline. This suggests that tissue stores of LPL become depleted. It has been argued that low molecular weight (LMW) heparins cause less disturbance of the LPL system than conventional heparin does.MethodsWe have followed LPL activity and TG during a dialysis-session with a LMW heparin (dalteparin) using the same patients and regime as in a previous study with conventional heparin, i.e. a primed infusion.ResultsThe shape of the curve for LPL activity resembled that during the earlier dialyses with conventional heparin, but the values were lower during dialysis with dalteparin. The area under the curve for LPL activity during the peak period (0–180 minutes) was only 27% and for the plateau period (180–240 minutes) it was only 36% of that observed with conventional heparin (p < 0.01). These remarkably low plasma LPL activities prompted us to re-analyze LPL activity and to measure LPL mass in frozen samples from our earlier studies. There was excellent correlation between the new and old values which rules out the possibility of assay variations as a confounding factor. TG increased from 2.14 mmol/L before, to 2.59 mmol/L after the dialysis (p < 0.01). From 30 minutes on, the TG values were significantly higher after dalteparin compared to conventional heparin (p < 0.05).ConclusionThese results indicate that LMW heparins disturb the LPL system as much or more than conventional heparin does.

Expression analyses of a rice 10 kDa sulfur-rich prolamin gene

Expression analyses of genes encoding sulfur-rich 10 kDa rice prolamins have not been reported to date although the entire genome of the model monocot plant has been sequenced in recent years. We isolated a 10 kDa rice prolamin gene, RP10, by genomic PCR, and the gene was registered in GenBank under the accession number AF294580. Genomic Southern-blot and bioinformatic study revealed that genes encoding RP10 homologes (class IV rice prolamins) were composed of two to three copies per haploid genome in Japonica cultivars Tainung 67 and Nipponbare. To elucidate the temporal and spatial expression of RP10, we introduced a chimeric gene that consisted of the 836 bp upstream sequence of RP10 and the coding regions of b-D-glucuronidase (GUS) into rice via Agrobacterium tumefaciens mediated transformation. The expression levels of GUS followed the accumulation pattern of endogenous RP10 transcript in parallel, indicating that the expression of GUS did reflect the endogenous temporal control of RP10 gene. Maximal GUS activity was reached at 12~20 days after flowering (DAF) in maturing seeds. Histochemical analysis showed that the specific expression of GUS in seeds was not restricted to the endosperm cells, but also occurred in the vascular bundle and epithelial cells of scutellum. In comparison with promoters of other rice storage protein genes, RP10 promoter exhibited a high expression level, with a long plateau period. Our studies suggest that RP10 promoter could be potentially useful for over-expression of foreign genes in transgenic rice seeds.

The simulation of the swelling and deswelling dynamics of gels

We have formulated the dynamics and the simulation scheme for large deformation of gels using the stress-diffusion coupling model [Yamaue, T., Taniguchi, T., and Doi, M., 2000, AIP Conference Proceedings, Vol. 519 (AIP), p. 584]. Using this model, we have simulated the deswelling process of 2D slab thermo-responsive gels undergoing spinodal decomposition, in comparison with the conventional collective diffusion model of gel networks. We reproduced the ‘plateau period’ due to the surface skin formation and the pattern formations in the inner region of gels by the stress-diffusion coupling model.

SX-EW copper and the technology cycle

Technology is viewed to advance through a series of cycles, starting with the emergence of a major breakthrough, followed by a period of ferment as alternate designs and improvements rapidly appear, leading to a dominant design, and then a long plateau period of minor incremental change. In this paper, the technology cycle model is applied to the history of solvent extraction electrowinning (SX-EW) processing of copper ore, which, along with other innovations, has transformed the US copper mining industry. The general framework of the technology cycle model holds, although there are differences relating to the specific nature of SX-EW processing. One particularly interesting difference is that SX-EW initially was complementary to the original method of ore processing, known as flotation. Only in recent years has it directly challenged flotation in the processing of supergene or transitional ore. In addition, the analysis shows that the SX-EW process helped the US producers maintain their competitiveness for at least a decade before the process was widely adopted by their main competitors, the Chilean producers. This raises questions about the widely held assumption that research and development of new innovations can provide firms and countries with little or no competitive advantage because new technologies diffuse very rapidly in today’s global economy.

Group I metabotropic glutamate receptors activate burst firing in rat midbrain dopaminergic neurons

We have investigated the changes in the spontaneous firing pattern induced by DHPG ((S)-3,5-dihydroxyphenylglycine) and NMDA (N-methyl-d-aspartic acid) on rat dopaminergic neurons in substantia nigra pars compacta (SNc) using sharp microelectrode recordings in in vitro conditions. Twenty-five out of 33 cells modified the regular single-pacemaker activity in burst firing when exposed to the Group I metabotropic glutamate receptor (mGluR) agonist DHPG (30 μM) and d-tubocurarine (500 μM) (d-TC), whereas they all fired in bursts during NMDA (20 μM) plus d-TC application. The blockade of SK-channels by d-TC and apamin was essential for the production of both types of bursts. Although the two drugs induced a similar number of action potentials per burst, the DHPG-induced bursts had a lower frequency, a longer duration and a longer plateau period without spikes. In addition, the DHPG-induced bursting had a longer wash-out, could be reduced or blocked by the mGluR 1 selective, non-competitive antagonist CPCCOEt (7-cyclopropan[b]chromen-1a-carboxylic acid ethyl ester) (100 μM) while it was not affected by the mGluR 5 selective antagonist MPEP (2-methyl-6-(phenylethynyl)-pyridine (10 μM). These results suggest that both the activation of glutamate metabotropic type 1 and NMDA ionotropic receptors induce burst firing in the dopaminergic cells of the ventral midbrain when the activity of the SK-channels is reduced.

Combination of alpha-stat strategy and hemodilution exacerbates neurologic injury in a survival piglet model with deep hypothermic circulatory arrest

Background. The optimal pH strategy and hematocrit during cardiopulmonary bypass with deep hypothermic circulatory arrest (DHCA) remain controversial. We studied the interaction of pH strategy and hematocrit and their combined impact on cerebral oxygenation and neurological outcome in a survival piglet model including monitoring by near-infrared spectroscopy (NIRS). Methods. Thirty-six piglets (9.2 ± 1.1 kg) underwent DHCA under varying conditions with continuous monitoring by NIRS (pH-stat or alpha-stat strategy, hematocrit 20% or 30%, DHCA time 60, 80, or 100 minutes). Neurological recovery was evaluated daily. The brain was fixed in situ on postoperative day 4 and a histological score (HS) for neurological injury was assessed. Results. Oxygenated hemoglobin (HbO 2) and total hemoglobin signals detected by NIRS were significantly lower with alpha-stat strategy during cooling ( p < 0.001), suggesting insufficient cerebral blood supply and oxygenation. HbO 2 declined to a plateau (nadir) during DHCA. Time to nadir was significantly shorter in lower hematocrit groups ( p < 0.01). Significantly delayed neurologic recovery was seen with alpha-stat strategy compared with pH-stat ( p < 0.05). The alpha-stat group had a worse histological score compared with those assigned to pH-stat ( p < 0.001). Neurologic impairment was estimated to be over 10 times more likely for animals randomized to alpha-stat compared with pH-stat strategy (odds ratio = 10.7, 95% confidence interval = 3.8 to 25.2). Conclusions. Combination of alpha-stat strategy and lower hematocrit exacerbates neurological injury after DHCA. The mechanism of injury is inadequate cerebral oxygenation during cooling and a longer plateau period of minimal O 2 extraction during DHCA.

Monolayer aggregation of a series of atypical amphiphilic β-diketone rare earth complexes at air/liquid interface

Monolayer aggregation of a series of atypical amphiphilic rare earth complexes REL 3Phen [RE=Eu(III), Sm(III), Tb(III); L=acac (acetylacetone), TFA (trifluoroacetylacetone), HFA (hexafluoroacetylacetone), TTA (thenoyltrifluoroacetone); Phen=1, 10-phenanthroline] were investigated at the air/liquid interface by π- A isotherms, Brewster angle microscopy (BAM) and transmission electron microscopy (TEM). When the complexes were mixed with arachidic acid (AA), respectively, stable monolayers could be formed. The rare earth complexes could be divided into two classes according to the π- A isotherm shape that whether there was a plateau period or not. Complexes with β-diketones acac, TFA and HFA were in one class, while complexes with the β-diketone TTA were in another. All the rare earth complexes formed microcrystals at the air/liquid interface. However, the former complex microcrystals oriented with the same crystal plane facing to all directions upon compression; while the latter complex microcrystals oriented with the same crystal plane facing to the same direction. Differences between monolayer behaviors of the two classes of complexes were discussed by comparing the structure of β-diketone ligands. A possible structural model of the rare earth complexes in the mixed monolayers with AA at air/liquid interface was proposed.

Learning to cruise: Bernstein's theory applied to skill acquisition during infancy

Cruising represents an important transition from quadrupedal to bipedal locomotion. While cruising, infants discover ways to control their trunks in upright. We predicted that the movement patterns infants demonstrated when learning to control the trunk in order to cruise and walk independently would reflect the process Bernstein [cf. N.B. Bernstein, The Coordination and Regulation of Movements, Pergamon Press, Oxford, England, 1967] proposed for adults' skill acquisition. In addition, we expected that infants would demonstrate a precursor poorly controlled exploratory phase, what we termed the “wobble phase”. We examined longitudinal changes in movement control of the thorax and pelvis from the onset of cruising through the onset of walking. Our findings suggest that learning to cruise involves an initial wobble phase followed by a gradual reduction in the wobble, or number of movement corrections. Finally a relative plateau period of control emerged with sporadic variability in the movement patterns of the thorax and pelvis. We suggest that the fact that infants did not show a phase in which they froze degrees of freedom was due to a lack of the minimum level of control one needs in order to do this. By the end of cruising, although functionally quite skillful, infants continued to demonstrate multiple and varied patterns of control. Infants limit the degrees of freedom just enough to successfully accomplish the task. We argue that variability remains due to: the minimal negative consequences of trunk inconsistency in this context given the available arm support; the trunk acts as a flexible interface for the, as yet, unstable coupling between the arms and legs; and the low number of constraints in relation to the multiple solutions that the task affords. Despite of the remaining variability, it appears that the control of the trunk acquired during cruising enables infants to shift into walking independently.

Effect of Sulfur on the Oxidation of Copper in Aqueous Solution

Combined ultrahigh vacuum electrochemistry is applied to study the effect of sulfur on copper oxidation in aqueous solution. Chronoamperametric studies show that pulsing a Cu electrode modified with ∼0.1 monolayer of adsorbed S results in an approximately 50 s plateau in the current‐time profile after a slight initial decay in current. Following the plateau period, the current‐time profile is observed to exhibit a final phase of current decay. In contrast, a S‐free copper electrode exhibits immediate current decay. X‐ray photoelectron spectroscopy analysis reveals that is the main oxide growing on both S‐free and S‐modified copper surfaces under these conditions. On the S‐free copper surface, oxide covers the surface almost immediately after the pulse. On the S‐modified copper surface, oxide growth continues for ∼70 s after the pulse. The data indicates that the final phase of current decay on the S‐modified Cu surface occurs only when oxide growth is essentially complete. Oxide growth is significantly retarded by the presence of sulfur. © 2000 The Electrochemical Society. All rights reserved.

Shrinking Process of Gels by Stress-Diffusion Coupled Dynamics

The dynamics of the volume-phase transition process of gels has been described by the collective diffusion model of the gel network, 1) which well reproduces the swelling process. But, it was found experimentally that the shrinking process is strongly decelerated and stopped transiently in a “plateau period” due to the formation of surface skin. In the end of the “plateau period”, various patterns appear and the gels restart to shrink. 2) These phenomena have not been reproduced theoretically. Here, we formulate the dynamics and the simulation scheme for large deformation of gels using the Stress-Diffusion Coupled Model, 3), 4) in which the continuity of solvent and the coupling between solvent diffusion and network stress are considered. Using this model we simulate the shrinking process of 2D slab gels undergoing spinodal decomposition by finite element method with delaunay triangulation.