Measurements of adsorption for membranes in situ with the use of time-lags and steady state flows

1979 ◽  
Vol 365 (1722) ◽  
pp. 267-281 ◽  
Keyword(s):  
Steady State ◽  
Standard Procedure ◽  
Time Lag ◽  
Sorption Isotherms ◽  
Time Lags ◽  
Carbon Membrane ◽  
Differential Diffusion ◽  
Use Of Time ◽  
Kinetics Of

Isotherms, steady state flows, the four time-lags, the kinetics of sorption and of the approach to the steady state of flow have been measured and analysed to investigate the properties of a graphitized carbon membrane. Sorption isotherms determined on the membrane in situ by a kinetic pro­cedure involving the time-lags and steady state flows were in agreement with isotherms determined by a standard procedure. Analysis of the time-lag and other results left the possibility of a small dependence of the diffusion coefficient, D , upon positional coordinate or upon time, but the dominant influence upon D was its dependence upon concentration, C . Differential diffusion coefficients increased very rapidly with C outside the range of the Henry law. Uptakes of diffusant in the steady state of flow, measured directly, through time-lag measurements and from steady state concentration contours across the membrane were in good agreement.

Nucleation rates and the kinetics of particle growth II. The birth and death process

1964 ◽  
Vol 277 (1369) ◽  
pp. 167-182 ◽  
Keyword(s):  
Steady State ◽  
Homogeneous Nucleation ◽  
Time Lag ◽  
Particle Growth ◽  
Statistical Problem ◽  
Death Process ◽  
Birth And Death Process ◽  
Growth Mechanisms ◽  
Nucleation Kinetics ◽  
Kinetics Of

The model considered in part I is generalized to include growth mechanisms in which the chemical reaction which proceeds at the particle-atm osphere interface is reversible, so that molecules may evaporate from a particle as well as condense upon it. The Becker-Döring-Zeldovich-Frenkel theory of homogeneous nucleation kinetics is then reviewed in the light of the known statistical problem of the birth -and -death process, and an improved approximation is introduced which significantly alters the calculated results. Both steady-state nucleation kinetics and the time lag problem are discussed.

scholarly journals Kinetics of activation and inactivation of swelling-stimulated K+/Cl- transport. The volume-sensitive parameter is the rate constant for inactivation.

1990 ◽  
Vol 95 (6) ◽  
pp. 1021-1040 ◽  
Author(s):  
M L Jennings ◽  
N al-Rohil
Keyword(s):  
Steady State ◽  
Rate Constants ◽  
Time Lag ◽  
Cell Swelling ◽  
Phosphatase Inhibitors ◽  
Kcl Transport ◽  
Lag Period ◽  
Activated Flux ◽  
Kinetics Of ◽  
Hypotonic Swelling

Red blood cells of several species are known to exhibit a ouabain-insensitive, anion-dependent K+ (Rb+) flux that is stimulated by cell swelling. We have used rabbit red cells to study the kinetics of activation and inactivation of the flux upon step changes in tonicity. Sudden hypotonic swelling (210 mosmol) activates the flux after a lag period of 10 min at 37 degrees C and 30-50 min at 25 degrees C. In cells that were preswollen to activate the transporter, sudden shrinkage (by addition of hypertonic NaCl) causes a rapid inactivation of the flux; the time lag for inactivation is less than 2 min at 37 degrees C. A minimal model of the volume-sensitive KCl transport system requires two states of the transporter. The activated (A) state catalyzes transport at some finite rate (turnover number unknown because the number of transporters is unknown). The resting (R) state has a much lower or possibly zero transport rate. The interconversion between the states is characterized by unimolecular rate constants R k12 in equilibrium with k21 A. The rate of relaxation to any new steady state is equal to the sum of the rate constants k12 + k21. Because the rate of transport activation in a hypotonic medium is lower than the rate of inactivation in an isotonic medium, we conclude that the volume-sensitive rate process is inactivation (the A to R transition); that is, cell swelling activates transport by lowering k21. Three phosphatase inhibitors (fluoride, orthovanadate, and inorganic phosphate) all inhibit the swelling-activated flux and also slow down the rate of approach to the swollen steady state. This finding suggests that a net dephosphorylation is necessary for activation of the flux and that the net dephosphorylation takes place as a result of swelling-induced inhibition of a kinase rather than stimulation of a phosphatase.

Studies on the freezing of pure liquids - II. The kinetics of homogeneous nucleation in supercooled liquids

1961 ◽  
Vol 261 (1305) ◽  
pp. 189-196 ◽  
Keyword(s):  
Time Lag ◽  
Supercooled Liquids ◽  
Time Lags ◽  
Nucleation Time ◽  
Initial State ◽  
Steady State Kinetic ◽  
Recent Developments ◽  
Dependent Flow ◽  
Kinetics Of ◽  
State Kinetic

A modified form of Turnbull & Fisher’s equation for the rate of nueleation in pure liquids is derived from the more general solution of Frenkel to the non-equilibrium steady -state kinetic problem . Recent developments in relaxation theory, based on the Zeldovich— Frenkel formulation of the time-dependent flow of embryos over the size variable g , show that under certain conditions the nucleation time lag may be exceedingly sensitive to the initial state of the condensing system. Frisch’s integral for the nucleation time lag is evaluated for two initial distributions of embryo size. The results, which are of general form, are used to derive expressions for the time lag in supercooled liquids. Methods are given for estimating certain parameters required in the computation of time lags in supercooled liquids.

scholarly journals Crystallization kinetics of amorphous calcium carbonate in confinement

2019 ◽  
Vol 10 (19) ◽  
pp. 5039-5043 ◽  
Author(s):  
Jack Cavanaugh ◽  
Michael L. Whittaker ◽  
Derk Joester
Keyword(s):  
Steady State ◽  
Calcium Carbonate ◽  
Crystal Nucleation ◽  
Amorphous Calcium Carbonate ◽  
Emulsion Droplets ◽  
Individual Crystal ◽  
Upper Limit ◽  
Kinetics Of

In situ observation of amorphous calcium carbonate (ACC) confined in ∼500 pL emulsion droplets allows determination of the timing of individual crystal nucleation events. Statistical analysis of events in hundreds of droplets establishes an upper limit for the steady-state nucleation rate of 1.2 cm−3 s−1 for the crystallization from ACC.

scholarly journals Impact of Water Deficit on Seasonal and Diurnal Dynamics of European Beech Transpiration and Time-Lag Effect between Stand Transpiration and Environmental Drivers

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3437
Author(s):  
Paulína Nalevanková ◽  
Zuzana Sitková ◽  
Jíři Kučera ◽  
Katarína Střelcová
Keyword(s):  
Soil Water ◽  
Water Deficit ◽  
Sap Flow ◽  
Time Lag ◽  
Global Radiation ◽  
Environmental Drivers ◽  
Time Lags ◽  
Soil Water Deficit ◽  
The Relationship

In-situ measurements of tree sap flow enable the analysis of derived forest transpiration and also the water state of the entire ecosystem. The process of water transport (by sap flow) and transpiration through vegetation organisms are strongly influenced by the synergistic effect of numerous external factors, some of which are predicted to alter due to climate change. The study was carried out by in-situ monitoring sap flow and related environmental factors in the years 2014 and 2015 on a research plot in Bienska dolina (Slovakia). We evaluated the relationship between derived transpiration of the adult beech (Fagus sylvatica L.) forest stand, environmental conditions, and soil water deficit. Seasonal beech transpiration (from May to September) achieved 59% of potential evapotranspiration (PET) in 2014 and 46% in 2015. Our study confirmed that soil water deficit leads to a radical limitation of transpiration and fundamentally affects the relationship between transpiration and environmental drivers. The ratio of transpiration (E) against PET was significantly affected by a deficit of soil water and in dry September 2015 decreased to the value of 0.2. The maximum monthly value (0.8) of E/PET was recorded in August and September 2014. It was demonstrated that a time lag exists between the course of transpiration and environmental factors on a diurnal basis. An application of the time lags within the analysis increased the strength of the association between transpiration and the variables. However, the length of these time lags changed in conditions of soil drought (on average by 25 min). Transpiration is driven by energy income and connected evaporative demand, provided a sufficient amount of extractable soil water. A multiple regression model constructed from measured global radiation (RS), air temperature (AT), and air humidity (RH) explained 69% of the variability in beech stand transpiration (entire season), whereas (RS) was the primary driving force. The same factors that were shifted in time explained 73% of the transpiration variability. Cross-correlation analysis of data measured in time without water deficit demonstrated a tighter dependency of transpiration (E) on environmental drivers shifted in time (−60 min RS, +40 min RH and +20 min vapour pressure deficit against E). Due to an occurrence and duration of soil water stress, the dependence of transpiration on the environmental variables became weaker, and at the same time, the time lags were prolonged. Hence, the course of transpiration lagged behind the course of global radiation by 60 (R2 = 0.76) and 80 (R2 = 0.69) minutes in conditions without and with water deficit, respectively.

In situ study of electron beam-induced chemical vapor deposition of Au in an environmental TEM

1995 ◽  
Vol 53 ◽  
pp. 256-257
Author(s):  
J. Drucker ◽  
R. Sharma ◽  
J. Kouvetakis ◽  
K.H.J. Weiss
Keyword(s):  
Electron Beam ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Quantum Effect ◽  
Line Drawing ◽  
Chemical Vapor ◽  
Environmental Cell ◽  
Engineering Changes ◽  
Kinetics Of

Patterning of metals is a key element in the fabrication of integrated microelectronics. For circuit repair and engineering changes constructive lithography, writing techniques, based on electron, ion or photon beam-induced decomposition of precursor molecule and its deposition on top of a structure have gained wide acceptance Recently, scanning probe techniques have been used for line drawing and wire growth of W on a silicon substrate for quantum effect devices. The kinetics of electron beam induced W deposition from WF6 gas has been studied by adsorbing the gas on SiO2 surface and measuring the growth in a TEM for various exposure times. Our environmental cell allows us to control not only electron exposure time but also the gas pressure flow and the temperature. We have studied the growth kinetics of Au Chemical vapor deposition (CVD), in situ, at different temperatures with/without the electron beam on highly clean Si surfaces in an environmental cell fitted inside a TEM column.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

Growth kinetics of Al2Cu in an Al-1.5Cu thin film by in Situ TEM

1993 ◽  
Vol 51 ◽  
pp. 1172-1173
Author(s):  
M. Park ◽  
S.J. Krause ◽  
S.R. Wilson
Keyword(s):  
Thin Film ◽  
In Situ Tem ◽  
Collector Plate ◽  
Transmission Electron ◽  
Device Processing ◽  
Corrosion Susceptibility ◽  
Precipitation Phenomena ◽  
Semiconductor Chips ◽  
Kinetics Of

Cu alloying in Al interconnection lines on semiconductor chips improves their resistance to electromigration and hillock growth. Excess Cu in Al can result in the formation of Cu-rich Al2Cu (θ) precipitates. These precipitates can significantly increase corrosion susceptibility due to the galvanic action between the θ-phase and the adjacent Cu-depleted matrix. The size and distribution of the θ-phase are also closely related to the film susceptibility to electromigration voiding. Thus, an important issue is the precipitation phenomena which occur during thermal device processing steps. In bulk alloys, it was found that the θ precipitates can grow via the grain boundary “collector plate mechanism” at rates far greater than allowed by volume diffusion. In a thin film, however, one might expect that the growth rate of a θ precipitate might be altered by interfacial diffusion. In this work, we report on the growth (lengthening) kinetics of the θ-phase in Al-Cu thin films as examined by in-situ isothermal aging in transmission electron microscopy (TEM).

In situ Time-Resolved Small-Angle X-ray Scattering Reveals the Formation Kinetics of Polyelectrolyte Complex Micelles

2019 ◽  
Author(s):  
Hao Wu ◽  
Jeffrey Ting ◽  
Siqi Meng ◽  
Matthew Tirrell
Keyword(s):  
Small Angle ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Polyelectrolyte Complex ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

We have directly observed the <i>in situ</i> self-assembly kinetics of polyelectrolyte complex (PEC) micelles by synchrotron time-resolved small-angle X-ray scattering, equipped with a stopped-flow device that provides millisecond temporal resolution. This work has elucidated one general kinetic pathway for the process of PEC micelle formation, which provides useful physical insights for increasing our fundamental understanding of complexation and self-assembly dynamics driven by electrostatic interactions that occur on ultrafast timescales.

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