Condensation Of Species Research Articles

1-D DSMC simulation of Io's atmospheric collapse and reformation during and after eclipse

A one-dimensional Direct Simulation Monte Carlo (DSMC) model is used to examine the effects of a non-condensable species on Io's sulfur dioxide sublimation atmosphere during eclipse and just after egress. Since the vapor pressure of SO 2 is extremely sensitive to temperature, the frost-supported dayside sublimation atmosphere had generally been expected to collapse during eclipse as the surface temperature dropped. For a pure SO 2 atmosphere, however, it was found that during the first 10 min of eclipse, essentially no change in the atmospheric properties occurs at altitudes above ∼ 100 km due to the finite ballistic/acoustic time. Hence immediately after ingress the auroral emission morphology above 100 km should resemble that of the immediate pre-eclipse state. Furthermore, the collapse dynamics are found to be greatly altered by the presence of even a small amount of a non-condensable species which forms a diffusion layer near the surface that prevents rapid collapse. It is found that after 10 min essentially no collapse has occurred at altitudes above ∼ 20 km when a nominal mole fraction of non-condensable gas is present. Collapse near the surface occurs relatively quickly until a static diffusion layer many mean free paths thick of the non-condensable gas builds up which then retards further collapse of the SO 2 atmosphere. For example, for an initial surface temperature of 110 K and 35% non-condensable mole-fraction, the ratio of the SO 2 column density to the initial column density was found to be 0.73 after 10 min, 0.50 after 30 min, and 0.18 at the end of eclipse. However, real gas species (SO, O 2) may not be perfectly non-condensable at Io's surface temperatures. If the gas species was even weakly condensable (non-zero sticking/reaction coefficient) then the effect of the diffusion layer on the dynamics was dramatically reduced. In fact, if the sticking coefficient of the non-condensable exceeds ∼0.25, the collapse dynamics are effectively the same as if there were no non-condensable present. This sensitivity results because the loss of non-condensable to the surface reduces the effective diffusion layer size, and the formation of an effective diffusion layer requires that the layer be stationary; this does not occur if the surface is a sink. Upon egress, vertical stratification of the condensable and non-condensable species occurs, with the non-condensable species being lifted (or pushed) to higher altitudes by the sublimating SO 2 after the sublimating atmosphere becomes collisional. Stratification should affect the morphology and intensity of auroral glows shortly after egress.

Postfrontal nanoparticles at Cape Grim: impact on cloud nuclei concentrations

Environmental context. Accurate prediction of climate change requires good knowledge of all the contributing processes; those processes controlling clouds and cloud properties are of particular importance. In this study the growth of bursts of nanometre-sized particles observed following cold fronts over the Southern Ocean was modelled to assess their importance as a source of cloud droplet nuclei. This showed that these post-frontal events were responsible for ~8% of the cloud nucleus population in winter but much less in summer. Abstract. Aerosol removal and growth rates were determined for the Cape Grim marine boundary layer (MBL) using local observations. Background particle growth rates, estimated using replacement of condensable sulfur species lost to particle removal are 0.04 nm h–1 (winter) and 0.17 nm h–1 (summer) and for post-frontal nucleation-events growth rates determined using evolution of the concentration ratio of particles with diameter >3 nm and 11 nm are ~0.3–0.4 nm h–1, consistent with reported high-latitude events. A box model using region-specific loss and growth rates predicts free-troposphere/MBL N3 ratios of 1.3–2.1 and 2.4–2.5 for background and event growth rates, compared with observations in the range of 0.7–1.5. Post-frontal nucleation events were found to contribute from <1 to ~8% of the CCN population depending on season and growth rate. However, these events help maintain the MBL Aitken population, contributing up to ~30%.

Charging of aerosol and nucleation in atmospheric pressure electrical discharges

The paper focuses on applications of atmospheric pressure plasmas (dc corona, streamer, spark and ac dielectric barrier discharges (DBDs)) in aerosol processes for materials and environment.Since aerosol kinematics depends mainly on electric forces acting on charged particles, the two mechanisms of aerosol charging by the collection of ions are presented in corona, post-corona and DBDs. In such defined charging conditions, field and diffusion charging laws are depicted, with respect to applications of controlled kinematics of charged aerosol.Then key parameters controlling the formation by nucleation and the growth by coagulation of particles in plasmas are presented. Sources of vapor leading to nucleated nanoparticles are depicted in atmospheric pressure electrical discharges: (i) when filamentary dc streamer and spark as well as ac-DBDs interact with metal or dielectric surfaces and (ii) when discharges induce reactions with gaseous precursors in volume. In both cases, condensable gaseous species are produced, leading to nano-sized particles by physical and chemical routes of nucleation. The composition, size and structure of primary nanoparticles as well as the final size of agglomerates are related to plasma parameters (energy, number per unit surface and time and thermal gradients around each filament as well as the transit time).

Astrophysical dust formation under the influence of temperature fluctuations

Context. Dust formation, i.e. the condensation of solid particles from a gas phase, occurs in astrophysical environments that are sufficiently cool and offer a sufficiently high density of condensable species. Since many astrophysical systems in which dust forms have turbulent features and the dust formation rates depend significantly on temperature, we investigate the influence of temperature fluctuations on dust condensation in dust-driven AGB winds. Aims. We present an approach for the time-dependent stochastic description of astrophysical dust formation and apply this in developing a fast algorithm, which is well suited for implementation into numerical models of dynamical AGB winds. The influence of the fluctuations on the dynamical structure is then investigated for a large sample of wind parameters. Methods. We employ a mathematical method, which describes the dust formation under the influence of random temperature fluctuations as a stochastic process. A system of Fokker-Planck equations for the one-point distribution function of the conjoint temporal development of temperature and dust results. Gas-box studies of this system have led us to a simplified microturbulent description for the implementation into time-dependent numerical wind models. Results. A method for the investigation of temperature fluctuations on dust formation is presented, which can be adapted to a variety of astrophysical situations. For dust-driven AGB winds, a microturbulent description turns out to be admissible. In AGB winds, rms-temperature fluctuations of 20–60 K can result in increased mass loss rates of 10–30% depending on the details of the physical model assumptions. Conclusions. The presented method for the treatment of temperature fluctuations with respect to dust formation has been succesfully applied to dynamical AGB winds. We suggest how to apply the method to other astrophysical systems. The influence of the fluctuations on the dynamics of dust-driven AGB winds is remarkable, but not overwhelming.

Kex1 Protease Is Involved in Yeast Cell Death Induced by Defective N-Glycosylation, Acetic Acid, and Chronological Aging

N-glycosylation in the endoplasmic reticulum is an essential protein modification and highly conserved in evolution from yeast to humans. The key step of this pathway is the transfer of the lipid-linked core oligosaccharide to the nascent polypeptide chain, catalyzed by the oligosaccharyltransferase complex. Temperature-sensitive oligosaccharyltransferase mutants of Saccharomyces cerevisiae at the restrictive temperature, such as wbp1-1, as well as wild-type cells in the presence of the N-glycosylation inhibitor tunicamycin display typical apoptotic phenotypes like nuclear condensation, DNA fragmentation, phosphatidylserine translocation, caspase-like activity, and reactive oxygen species accumulation. Since deletion of the yeast metacaspase YCA1 did not abrogate this death pathway, we postulated a different proteolytic process to be responsible. Here, we show that Kex1 protease is involved in the programmed cell death caused by defective N-glycosylation. Its disruption decreases caspase-like activity, production of reactive oxygen species, and fragmentation of mitochondria and, conversely, improves growth and survival of cells. Moreover, we demonstrate that Kex1 contributes also to the active cell death program induced by acetic acid stress or during chronological aging, suggesting that Kex1 plays a more general role in cellular suicide of yeast.

Multivariate analysis of homogeneous nucleation rate measurements. Nucleation in the p-toluic acid/sulfuric acid/water system

Recent kinetic extensions of the nucleation theorem suggest that the logarithm of the steady-state nucleation rate has strong multilinear dependence on the log concentrations of condensable species present in the vapor phase. A further remarkable result is that the coefficients of this linear dependency provide a direct determination of the molecular content of the critical nucleus itself. Building on these results, the powerful utility of multivariate statistical methods is demonstrated here for physically based parametrization and interpretation of nucleation rate measurements. The new approach is applied to recent measurements by Zhang et al. [Science 304, 1487 (2004)] on the p-toluic acid/sulfuric acid/water ternary vapor system. A linear minimum variance parametrization for nucleation rate dependence on vapor composition, accurate over the range of the measurements, is obtained. Estimates of critical nucleus molecular composition are also presented. These suggest that a single molecule of p-toluic acid present in the critical nucleus is sufficient to trigger a ternary nucleation event. Efforts under way to apply the new methods to analysis of new particle formation in the atmosphere are discussed.

Oxygen and Other Volatiles in the Giant Planets and their Satellites

Giant planet atmospheric composition and satellite densities provide insights into protoplanetary disk conditions. Abundances of condensable species and noble gases in wellmixed atmospheres can distinguish among several giant planet formation scenarios, and satellite densities are fi rst order measurements of ice:rock ratios. Recent work on protosolar abundances, relying on three-dimensional spectroscopic modeling of the solar photosphere, provides the framework for the interpretation of measurements. Model densities of protoplanetary disk condensates are shown as a function of carbon partitioning between CO, CH4 and organics. Comparison with observed satellite densities shows that Saturn’s icy satellites are inconsistent with solar composition, and must either have formed in a water-rich environment or have suffered a complex collisional history. The larger satellites of the giant planets are consistent with solar composition, with densities that speak of variation in the partitioning of carbon.

Secondary organic aerosol in the global aerosol – chemical transport model Oslo CTM2

Abstract. The global chemical transport model Oslo CTM2 has been extended to include the formation, transport and deposition of secondary organic aerosol (SOA). Precursor hydrocarbons which are oxidised to form condensible species include both biogenic species such as terpenes and isoprene, as well as species emitted predominantly by anthropogenic activities (toluene, m-xylene, methylbenzene and other aromatics). A model simulation for 2004 gives an annual global SOA production of approximately 55 Tg. Of this total, 2.5 Tg is found to consist of the oxidation products of anthropogenically emitted hydrocarbons, and about 15 Tg is formed by the oxidation products of isoprene. The global production of SOA is increased to about 69 Tg yr−1 by allowing semi-volatile species to partition to ammonium sulphate aerosol. This brings modelled organic aerosol values closer to those observed, however observations in Europe remain significantly underestimated. Allowing SOA to partition into ammonium sulphate aerosol increases the contribution of anthropogenic SOA from about 4.5% to 9.4% of the total production. Total modelled organic aerosol (OA) values are found to represent a lower fraction of the measured values in winter (when primary organic aerosol (POA) is the dominant OA component) than in summer, which may be an indication that estimates of POA emissions are too low. Additionally, for measurement stations where the summer OA values are higher than in winter, the model generally underestimates the increase in summertime OA. In order to correctly model the observed increase in OA in summer, additional SOA sources or formation mechanisms may be necessary. The importance of NO3 as an oxidant of SOA precursors is found to vary regionally, causing up to 50%–60% of the total amount of SOA near the surface in polluted regions and less than 25% in more remote areas, if the yield of condensible oxidation products for β-pinene is used for NO3 oxidation of all terpenes. Reducing the yield for α-pinene and limonene oxidation in line with recent measurements reduces the global fraction of SOA formed from NO3 oxidation products from 27% to about 21%. This study underscores the need for SOA to be represented in a more realistic way in global aerosol models in order to better reproduce observations of organic aerosol burdens in industrialised and biomass burning regions.

Spectroscopic studies of triethoxysilane sol–gel and coating process

Silica sol–gels have been prepared under different conditions using triethoxysilane (TES) as precursor. The prepared sol–gels have been used to coat aluminum for corrosion protection. Vibrational assignments have been made for most vibration bands of TES, TES sol–gel, TES sol–gel-coated aluminum and xerogel. It has been noticed that air moisture may have helped the hydrolysis of the thin coating films. Xerogels have been obtained from the sol–gel under different temperature conditions and the resulting samples have been characterized by using infrared and Raman spectroscopic methods. IR data indicate that the sol–gel process is incomplete under the ambient conditions although an aqueous condition can have slightly improved the process. Two nonequivalent silicon atoms have been identified from the collected 29Si NMR spectra for the sol–gel, supporting the result derived from the IR data. The frequency of Si H bending vibration has been found to be more sensitive to the skeletal structure than that of the Si H stretching vibration. A higher temperature condition could favor the progression of hydrolysis and condensation. A temperature higher than 300 °C would cause sample decomposition without seriously damaging the silica network. From infrared intensity measurements and thermo-gravimetric analyses, the fractions of incomplete hydrolysis and condensation species have been estimated to be 4% and 3%, respectively. Electrochemical data have shown that the sol–gel coating significantly improves the corrosion protection properties of aluminum.

Effect of Fuel/Air Ratio and Aromaticity on Sooting Behavior of Premixed Heptane Flames

Oxidation and pyrolysis products were sampled and quantified along the axis of premixed laminar flames burning n-heptane in slightly sooting (C/O = 0.7) and heavily sooting conditions (C/O = 0.8) by means of gas chromatographic analysis. Total particulate was extracted with dichloromethane (DCM) in order to separate condensed species (CS) including polycyclic aromatic hydrocarbons from soot. The effect of aromatic addition (10 vol % of n-propylbenzene) to n-heptane fuel in heavily sooting conditions on the distribution of light hydrocarbons was also studied. Detailed modeling extended to the formation of high-molecular-weight species and soot was performed to verify the effect of the C/O ratio and of the fuel aromatic content on soot formation. The C/O ratio was found to affect benzene formation which in turn caused an increase of condensed species and soot formation rates. The fuel aromaticity was found to shift soot inception upstream in the flame increasing soot in the oxidation region of the flame. However, aromaticity was not found to influence the ultimate soot loading because of the reduced soot growth rate due to the slightly lower temperature and lower acetylene formation in the aromatic-doped flame. The model was used to explore the effect of larger amounts of aromatics on soot formation. Increased benzene and condensed species, including polycyclic aromatic hydrocarbons, are obtained from the addition of more aromatics (>10%) to n-heptane resulting in higher ultimate soot loading, confirming the direct relation between gas-phase aromatics and final soot loading.

Aerosols at a mountaintop observatory in Arizona

This paper discusses physics of aerosols measured at the summit of Mt. Lemmon, Arizona (2790 m), from February to May 2002, where “clean” air representative of the free troposphere sometimes occurs. We confirmed Marti's findings of a persistent daily variation in the number concentration of condensation nuclei (diameter > 10 nm), with a strong maximum occurring in the afternoon and minimum in the early morning. These particles show evidence of growth at rates of 10–23 nm per hour. The diurnal variation was present even on days when the planetary boundary layer remained below the mountain. From the rate of growth and Maxwellian diffusion theory, we deduce that precursor condensable species are present in daytime concentrations of 107–108 cm−3, and that these are produced at a rate of 105–106 cm−3 s−1. Increased convection caused by solar heating of the mountain often carries contaminated air to the summit. Yet only a small (factor of 1.5) diurnal pattern was found for accumulation mode (diameter ∼ 130 nm) particles on days where the convective boundary layer passed well above the station. We hypothesize that these long‐lived (e.g., several days) aerosols are pumped into the free troposphere and remain behind at night in a residual layer. The free tropospheric aerosol size distribution measured at Mt. Lemmon was similar in shape but higher in magnitude (by around 50%) than at Jungfraujoch in the Swiss Alps (3580 m). There is much greater diurnal variation in Aitken‐sized particles (daily factor of from 7 to 10) at Mt. Lemmon than observed at Jungfraujoch (factor of from 1.0 to 1.6), evidently arising from stronger photochemical rate of productions of precursor gases.

Silica‐Based Mesoporous Organic–Inorganic Hybrid Materials

Mesoporous organic-inorganic hybrid materials, a new class of materials characterized by large specific surface areas and pore sizes between 2 and 15 nm, have been obtained through the coupling of inorganic and organic components by template synthesis. The incorporation of functionalities can be achieved in three ways: by subsequent attachment of organic components onto a pure silica matrix (grafting), by simultaneous reaction of condensable inorganic silica species and silylated organic compounds (co-condensation, one-pot synthesis), and by the use of bissilylated organic precursors that lead to periodic mesoporous organosilicas (PMOs). This Review gives an overview of the preparation, properties, and potential applications of these materials in the areas of catalysis, sorption, chromatography, and the construction of systems for controlled release of active compounds, as well as molecular switches, with the main focus being on PMOs.

Influence of relative humidity upon pollution and dust during ACE‐Asia: Size distributions and implications for optical properties

An extensive set of aerosol physical and optical measurements was taken over the waters east of Asia during the Aerosol Characterization Experiment‐Asia (ACE‐Asia) project in the spring of 2001. Dust storms upwind of the study area combined with intense pollution plumes from coastal cities yielded an opportunity to examine both types of aerosol, in isolation and as they interacted. Scattering calculated from aerosol size distributions measured with an optical particle counter agreed well with simultaneous nephelometer measurements. We periodically heated sample air to evaporate sulfates and organic material. The change in volume upon heating agreed well with simultaneous measurements of aerosol composition. This volatile material was distributed on dust in rough proportion to surface area. Here we use the particle size and composition data to improve estimates of scattering at ambient humidity and to examine the effects of mixing on the optical properties of both pollution and dust aerosols. The presence of dust results in uptake of soluble and condensible species onto its surface and thereby reduces the mass scattering efficiency of the pollution aerosol by 50% and suppresses the change in scattering due to relative humidity (f(RH)) by up to 35%.

Thermodynamics of the formation of atmospheric organic particulate matter by accretion reactions—2. Dialdehydes, methylglyoxal, and diketones

Predicting the formation of organic particulate matter (OPM) in the atmosphere by absorptive gas/particle partitioning requires a knowledge of the identities, atmospheric levels, and physical properties of all condensable species. Data from field and chamber experiments have shown that a portion of atmospheric OPM samples are comprised of products generated during oxidation of volatile organic compounds. It has been suggested that some of these initially formed oxidation products also contribute to the formation of atmospheric OPM via molecular-weight (MW) building “accretion reactions”. The role of such reactions as well as a general theoretical approach for evaluating their thermodynamic relevance in regard to atmospheric OPM formation, have been discussed in prior work. This work utilizes that approach in considerations of accretion reactions of glyoxal, two other dialdehydes, methylglyoxal, and two diketones. The methods used to predict free energy of formation ( Δ G f ° ) values (and hence equilibrium constant ( K ) values) indicate that: (1) for 1,4-butanedial, 2,3-butanedione, and 2,5-hexanedione, the accretion reactions considered are not favorable; (2) for C 6 and higher dialdehydes, reaction by aldol condensation may contribute to atmospheric OPM formation under certain circumstances, if kinetically favorable; and (3) for glyoxal, diol and subsequent oligomer formation, and for methylglyoxal, aldol condensation, are thermodynamically favorable, and may contribute significantly to OPM in the atmosphere, if kinetically favorable.

Trend Analysis for Atmospheric Hydrocarbon Partitioning Using Continuous Thermodynamics

Abstract The partitioning of atmospheric hydrocarbons into vapor and condensed phases when the species count is large is considered using the formalism of continuous thermodynamics. The vapor saturation pressures and condensate species distribution are parameterized using the species normal boiling temperatures. Qualitative trends in activity coefficient values and phase equilibrium behavior that are relevant to the outer planets and Titan are discussed in terms of a much simplified perspective on these aspects of partitioning. The trends found are generally consistent with those from other published atmospheric model results.

Calculation of soret‐shifted dew points by continuous mixture thermodynamics

AbstractSoret‐induced local concentration changes, very large numbers of condensable species, and condensate nonideality combine to make the calculation of isobaric dew‐point surface temperatures, Tdp, and corresponding incipient condensate compositions (xi, i = 1, 2, …, N) nontrivial, even with advanced computational methods. As usual in the canonical isobaric “dew‐point ” situation, the mainstream vapor mixture state [composition yi (i = 1, 2, …, N), T, and p] is fully specified. We consider here, for illustrative purposes, the tractable but frequently encountered limiting case of a very large number (perhaps dozens, if not hundreds) of condensable, nonreacting species that are members of a homologous series (such as n‐alkanes in a fuel “blend”), dilute in a “noncondensable ” carrier gas (such as N2). Pseudo‐binary Ludwig–Soret coefficients for the vapor phase are estimated from the corresponding Schmidt numbers and gas‐kinetic theory. As in our earlier studies (which emphasized binary “regular ” solutions of alkali sulfates), of particular current interest is the extent of systematic Soret‐induced shifts in the predicted dew‐point (wall) temperature and associated condensate composition/properties (such as viscosity). This often‐overlooked feature removes the present class of univariate problems from the province of classical continuous thermodynamics. Three efficient continuous mixture theory (CMT)–based computational methods are proposed/illustrated/compared, two moment‐based, and all exploiting Gaussian quadratures. We find that accurate results can be obtained while avoiding prescribing the shape of the distribution function in the condensate, using as few as three to four rationally selected “pseudo‐components.” © 2005 American Institute of Chemical Engineers AIChE J, 2005

Particle characterization from two-stroke powered two-wheelers

This paper presents the physical characterization of particle emissions from small two-stroke gasoline two-wheelers. Particle samples were drawn with a dedicated partial dilution system. They were analysed with various aerosol measurement instruments, including a scanning mobility particle sizer (SMPS), an electrical low-pressure impactor (ELPI), and a diffusion charger. Solid particles were discriminated by using a thermodenuder. Results suggest that small two-wheeled vehicles are significant emitters of both solid and volatile particles with the volatile fraction being the dominant one. The particle size distribution appears bimodal at high load and log-normal at lower load. The high concentration of condensable species in the exhaust also leads to the formation of volatile particles in the accumulation mode, which is typically not observed in diesel exhaust. Further comparison with a typical diesel passenger car revealed that some older technology two-wheelers emit even higher mass and solid particle counts than the car. However, the paper concludes that technology improvements such as oxidation catalysts and direct injection systems are expected significantly to reduce particulate matter emission rates.

Representation of Secondary Organic Aerosol Laboratory Chamber Data for the Interpretation of Mechanisms of Particle Growth

Absorptive models of gas-particle partitioning have been shown to be successful in describing the formation and growth of secondary organic aerosol (SOA). Here the expression for particle growth derived by Odum et al. (Odum, J. R.; Hoffmann, T.; Bowman, F.; Collins, D.; Flagan, R. C.; Seinfeld, J. H. Gas/particle partitioning and secondary organic aerosol yields. Environ. Sci. Technol. 1996, 30, 2580-2585) is extended to facilitate interpretation of SOA growth data measured in the laboratory in terms of the underlying chemistry, even when details of the reactions are not well-constrained. A simple (one-component) expression for aerosol growth (deltaM) as a function of the amount of hydrocarbon reacted (deltaHC) is derived, and the effects of changes to three key parameters, stoichiometric yield of condensable species, gas-particle partitioning coefficient, and concentration of preexisting aerosol, are discussed. Two sets of laboratory chamber data on SOA growth are examined in this context: the ozonolysis of alpha-pinene and the OH-initiated photooxidation of aromatic compounds. Even though these two systems have a number of significant differences, both are described well within this framework. From the shapes of the deltaM versus deltaHC curves in each case, the importance of poorly constrained chemistry such as heterogeneous reactions and gas-phase reactions of oxidation products is examined.

Jupiter After the Galileo Probe

The Galileo Mission to Jupiter, which arrived in December of 1995, provided the first study by an orbiter, and the first in-situ sampling via an entry probe, of an outer planet atmosphere. The rationale for an entry probe is that, even from an orbiter, remote sensing of the Jovian atmosphere could not adequately retrieve the information desired. This talk provides a current summary of the most significant aspects of the data returned from the Galileo entry probe. As a result of the probe measurements, there has been a reassessment of our understanding of outer planet formation and evolution of the solar system. The primary scientific objective of the Galileo probe was to determine the composition of the Jovian atmosphere, which from remote sensing remained either very uncertain, or completely unknown, with respect to several key elements. For example, the O abundance, in the form H2O, was uncertain by two orders of magnitude. Only a highly depleted upper abundance limit obtained near the 1 bar pressure level was known for S, and abundances of noble gases heavier than He were unknown. The probe found that the global He mass fraction is significantly above the value reported from the Voyager Jupiter flybys but is slightly below the protosolar value, implying that there has been some settling of He to the deep Jovian interior. The probe He measurements have also led to a reevaluation of the Voyager He mass fraction for Saturn, which is now determined to be much closer to that of Jupiter. The elements C, N, S, Ar, Kr, Xe were all found to have global abundances approximately 3 times their respective solar abundances. This result has raised a number of fundamental issues with regard to properties of planetesimals and the solar nebula at the time of giant planet formation. The global abundance of O was not obtained by the probe because of the influence of local processes at the probe entry site (PES), processes which depleted condensible species, in this case H2O, well below condensation levels. Other condensible species, namely NH3 and H2S, were similarly affected but attained their deep equilibrium mixing ratios before the maximum depth sampled by the probe. Processes that might be capable of producing such effects on the condensibles are still under investigation. Measured isotopic ratios of noble gases and other heavy elements are solar, and (D + 3He)/H is the same to within measurement uncertainties as in the local interstellar medium. No thick clouds were detected, and in particular no significant water cloud, but the PES location clearly affected the probe measurements of clouds. In fact, the probe data must be understood in the context of the location of the PES, which was within what is termed a 5 μm hot spot, a local clearing in the clouds that is bright near the 5 μm spectral region. The thermal structure at the PES was determined from approximately 1000 km above the 1 bar pressure level (10−9 bars) to 132 km below 1 bar (22 bars). Probe measurements showed the atmosphere to be generally stably stratified as deep as the probe made measurements, with a typical static stability of ~0.1 K km−1 at and below visible cloud levels. In the upper atmosphere the probe derived a maximum positive vertical temperature gradient of approximately 5 K km−1, and maximum temperature of ~900 K. The energy sources producing the warm upper atmosphere have yet to be completely identified. At first glance, Doppler tracking of the probe indicates that the long observed cloud level zonal winds extend to levels at least as deep as the probe made measurements. Zonal wind increases from ~80 m s−1 at pressures less than a bar to about 180 m s−1 near 5 bars, and remains approximately constant with depth thereafter. However, there is a question as to whether the winds measured from probe tracking are representative of the general wind field, or are considerably influenced by localized winds associated with the PES.

Taxonomy of nucleation and growth processes in isotropic systems

We construct a taxonomy of transient behavior for one component coupled nucleation and growth based on linear and nonlinear stability analysis of a two species model. The two species are the condensable species and the condensed droplets or particles, respectively. Our model reproduces previously reported asymptotically stable and oscillatory transient nucleation behavior. Additionally, we show previously unreported possibilities of multiple stationary states and combinations of stationary states with limit cycles. We predict that multiple stationary states may be observed under near critical conditions. Estimates of suitable conditions for experimental verification are given for several systems of interest.