Dynamic Equilibrium System Research Articles

Farthest Neighbor: The Distant Milky Way Satellite Eridanus II*

Abstract We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite Eridanus II (Eri II). We identify 28 member stars in Eri II, from which we measure a systemic radial velocity of and a velocity dispersion of . Assuming that Eri II is a dispersion-supported system in dynamical equilibrium, we derive a mass within the half-light radius of , indicating a mass-to-light ratio of / and confirming that it is a dark matter-dominated dwarf galaxy. From the equivalent width measurements of the Ca triplet lines of 16 red giant member stars, we derive a mean metallicity of [Fe/H] = −2.38 ± 0.13 and a metallicity dispersion of . The velocity of Eri II in the Galactic standard of rest frame is v GSR = −66.6 , indicating that either Eri II is falling into the Milky Way potential for the first time or that it has passed the apocenter of its orbit on a subsequent passage. At a Galactocentric distance of ∼370 kpc, Eri II is one of the Milky Way’s most distant satellites known. Additionally, we show that the bright blue stars previously suggested to be a young stellar population are not associated with Eri II. The lack of gas and recent star formation in Eri II is surprising given its mass and distance from the Milky Way, and may place constraints on models of quenching in dwarf galaxies and on the distribution of hot gas in the Milky Way halo. Furthermore, the large velocity dispersion of Eri II can be combined with the existence of a central star cluster to constrain massive compact halo object dark matter with mass ≳10 .

Microencapsulation and characterization of liposomal vesicles using a supercritical fluid process coupled with vacuum-driven cargo loading

A new technique of liposomal microencapsulation, consisting of supercritical fluid extraction followed by rapid expansion of the supercritical solution and vacuum-driven cargo loading, was successfully developed. It is a continuous flow-through process without usage of any toxic organic solvent. For use as a coating material, the solubility of soy phospholipids in supercritical carbon dioxide was first determined using a dynamic equilibrium system and the data was correlated with the Chrastil model with good agreement. Liposomes were made with D-(+)-glucose as a cargo and their properties were characterized as functions of expansion pressure, temperature, and cargo loading rates. The highest encapsulation efficiency attained was 31.7% at the middle expansion pressure of 12.41MPa, highest expansion temperature of 90°C, and lowest cargo loading rate of 0.25mL/s. The large unilamellar vesicles and multivesicular vesicles were observed to be a majority of the liposomes produced using this eco-friendly process.

When the Jeans Do Not Fit: How Stellar Feedback Drives Stellar Kinematics and Complicates Dynamical Modeling in Low-mass Galaxies

Abstract In low-mass galaxies, stellar feedback can drive gas outflows that generate non-equilibrium fluctuations in the gravitational potential. Using cosmological zoom-in baryonic simulations from the Feedback in Realistic Environments project, we investigate how these fluctuations affect stellar kinematics and the reliability of Jeans dynamical modeling in low-mass galaxies. We find that stellar velocity dispersion and anisotropy profiles fluctuate significantly over the course of galaxies’ starburst cycles. We therefore predict an observable correlation between star formation rate and stellar kinematics: dwarf galaxies with higher recent star formation rates should have systemically higher stellar velocity dispersions. This prediction provides an observational test of the role of stellar feedback in regulating both stellar and dark-matter densities in dwarf galaxies. We find that Jeans modeling, which treats galaxies as virialized systems in dynamical equilibrium, overestimates a galaxy’s dynamical mass during periods of post-starburst gas outflow and underestimates it during periods of net inflow. Short-timescale potential fluctuations lead to typical errors of ∼20% in dynamical mass estimates, even if full three-dimensional stellar kinematics—including the orbital anisotropy—are known exactly. When orbital anisotropy is not known a priori, typical mass errors arising from non-equilibrium fluctuations in the potential are larger than those arising from the mass-anisotropy degeneracy. However, Jeans modeling alone cannot reliably constrain the orbital anisotropy, and problematically, it often favors anisotropy models that do not reflect the true profile. If galaxies completely lose their gas and cease forming stars, fluctuations in the potential subside, and Jeans modeling becomes much more reliable.

Hydroelastic response of marine risers subjected to internal slug-flow

It is the purpose of this study to investigate the dynamic behaviour of catenary pipelines for marine applications, assuming the combined effect of harmonic motions imposed at the top, and the internal slug-flow. The analysis is based on the assumption of a steady slug-flow inside the pipe that results in a relatively simplified model for the formulation of the internal flow. The slug-flow model is described using several assumptions and empirical correlations which attempt to reveal the ill-understood and concealed properties of the slug-flow. The pipeline dynamics are investigated in the two dimensional space omitting the out-of-plane vibrations. The system of differential equations is generic and accounts for the steady effect of the internal liquid as is conveyed through the structure.The two models, those of the internal slug-flow and the pipeline’s dynamical model, are properly combined through the internal flow terms of the dynamic equilibrium system. The solution provided is achieved using a frequency domain technique which is applied to the linearized governing set. The effect of the slug-flow is assessed through comparative computations with and without internal flow effects. The conclusions are drawn having the structure excited under axial and normal motions paying particular attention to the variation of the dynamic components along the complete length of the pipeline.

Paper spray mass spectrometry applied in the monitoring of a chemical system in dynamic chemical equilibrium: the redox process of methylene blue.

The monitoring of chemical systems in dynamic equilibrium is not an easy task. This is due to the high rate at which the system returns to equilibrium after being perturbed, which hampers the possibility of following the aftereffects of the disturbance. In this context, it is necessary to use a fast analytical technique that requires no (or minimal) sample preparation, and which is capable of monitoring the species constituting the system in equilibrium. Paper spray ionization mass spectrometry (PS-MS), a recently introduced ambient ionization technique, has such characteristics and hence was chosen for monitoring a model system: the redox process of methylene blue. The model system evaluated herein was composed of three cationic species of methylene blue (MB), which coexist in a dynamic redox system: (1) [MB](+) of m/z 284 (cationic MB); (2) [MB + H + e](+•) of m/z 285 (the protonated form of a transient species resulting from the reduction of [MB](+) ); (3) [MB + 2H + 2e](+) or [leuco-MB + H](+) of m/z 286 (the protonated leuco form of MB). Aliquots of a MB solution were collected before and after the addition of a reducing agent (metallic zinc) and directly analyzed by PS-MS for identification of the predominant cationic species at different conditions. The mass spectra revealed that before the addition of the reducing agent the ion of m/z 284 (cationic MB) is the unique species. Upon the addition of the reducing agent and acid, however, the solution continuously undergo discoloration while reduced species derived directly from cationic MB (m/z 285 and 286) are detected in the mass spectra with increasing intensities. Fragmentation patterns obtained for each ionic species, i.e. [MB](+) , [MB + H + e](+•) and [leuco-MB + H](+) , shown to be consistent with the proposed structures. The PS-MS technique proved to be suitable for an in situ and 'near' real-time analysis of the dynamic equilibrium involving the redox of MB in aqueous medium. The data clearly demonstrated how the redox equilibrium shifts depending on the disturbance caused to the system.

Effect of tube heat conduction on the single branch pulsating heat pipe start-up

The oscillation inception in the single-branch pulsating heat pipe (PHP, called also oscillating heat pipe) has been studied in the presence of the heat conduction along the PHP tube, with the imposed both evaporator heat power and condenser temperature. A start-up regime caused rather by the meniscus/film evaporation than boiling has been considered. The dynamic equilibrium system state has been analyzed, where the liquid film is absent and the meniscus is located at a position where the tube temperature corresponds to the saturation temperature. The temporal evolution of the system responding to an initial fluctuation shows a non-linear response even for small fluctuations. The stability of the equilibrium state has been analyzed. The stability threshold corresponds to the start-up criterion. The main result of the above analysis is the independence of the start-up criterion of the liquid film properties (film shape and thickness). This result applies to the multi-branch PHP too. Due to the large tube thermal inertia, influence of the temporal variation of the tube temperature on the threshold can be neglected; only the equilibrium spatial temperature distribution along the tube matters. The start-up threshold value is determined for the temperature gradient along the tube, more specifically, its equilibrium value at the equilibrium meniscus location. It depends only weakly on other system parameters like condenser temperature or adiabatic section length. An analytical expression for the threshold has been obtained. The start-up power scales like square root of the tube heat conductivity. The liquid viscous dissipation is found to be much less important than the energy dissipation via the fluid and solid heat transfer.

Theoretical investigation on isomer formation probability and free energy of small C clusters**Project supported by the National Natural Science Foundation of China (Grant No. 11304239) and the Fundamental Research Funds for the Central Universities.

Molecular dynamics simulations and free energy calculations are employed to investigate the evolution, formation probability, detailed balance, and isomerization rate of small C cluster isomer at 2500 K. For C10, the isomer formation probability predicted by free energy is in good agreement with molecular dynamics simulation. However, for C20, C30, and C36, the formation probabilities predicted by free energy are not in agreement with molecular dynamics simulations. Although the cluster systems are in equilibrium, detailed balance is not reached. Such results may be attributed to high transformation barriers between cage, bowl, and sheet isomers. In summary, for mesoscopic nanosystems the free energy criterion, which commonly holds for macroscopic systems in dynamic equilibrium, may not provide a good prediction for isomer formation probability. New theoretical criterion should be further investigated for predicting the isomer formation probability of a mesoscopic nanosystem.

An intergenerational transmission of sustainability? Ancestral habitus and food production in a traditional agro-ecosystem of the Upper Guinea Forest, West Africa

The need for sustainable alternatives to industrial farming has led to a revival of interest in traditional agro-ecosystems. Whilst it is well recognised that traditional agro-ecosystems are both social and physical–technical – few case studies have examined interactions between both these dimensions in a single system. For a system to be considered sustainable it needs to be shown to have retained key characteristics over several generations. Case studies therefore demand a location where intergenerational transmission of agro-ecological knowledge and practice is ongoing. This paper examines the intergenerational transmission of social and physical–technical dimensions of a traditional agro-ecosystem of the Loma people in NW Liberia. We engage an innovative interdisciplinary combination of methodologies in analyzing interactions between: (i) energy efficiencies (yield to labour) in 3 different Loma food production systems, using longitudinal quantitative surveys, and, (ii) the social institutions that mediate food production practice, using qualitative methods. Our energy efficiency calculations show that AfDE cultivation is more than twice as efficient at producing calories as either shifting cultivation or forest and river extractivism, yet GPS mapping demonstrates that AfDE cultivation is highly spatially restricted despite clear opportunities for expansion and optimisation. This raises an important question: why have the Loma not expanded AfDE cultivation? We propose that despite being fully aware of the opportunities AfDEs present, a Loma ‘ancestral habitus’ and substantive economic rationality restrict areal expansion and optimisation of AfDE cultivation, curtailing growth and structuring a social-ecological system in dynamic equilibrium. Our findings underline that sustainability is not simply a physio-technical issue; social and belief issues appear to be far more important in framing behaviour in traditional agro-ecosystems.

Fisopatología de la adaptación a la altura

La posicion básica del investigador tratándose de la adaptación a la altura de las razas existentes desde una época prehistórica, debe establecerse sobre el concepto de aclimatación, que lleva inmanente la capacidad indiscutible de vivir y reproducirse. Por consiguiente, el planteamiento del problema supone estudiar los climas de altitud y las características biológicas de los seres que la habitan; esto es, los mecanismos funcionales dé integración entre organismo y ambiente. Se trata de considerar como punto de partida, unidades bioclimáticas que constituyen sistemas fisiológicos en equilibrio dinámico adaptados a vivir desde el nivel del mar quizá por encima de 5,300 metros de altitud (Bowman), que tal puede ser el ecúmene de la raza humana.

Modeling of Interannual Snow and Ice Storage in High-Altitude Regions by Dynamic Equilibrium Concept

AbstractThe energy and mass balance model for terrestrial ice and snow is an essential tool for the future projection of interannual snow and ice storage including glaciers. However, the snow models in the hydrologic engineering field have barely considered the long-term behavior of the snow and ice storage because the time scale of glacier dynamics is much longer than those of river flow and seasonal snowmelt. This paper proposes an appropriate treatment for inland glaciers as systems in dynamic equilibrium that stay constant under a static climate condition. It is conjectured that the snow and ice vertical movement from high-elevation areas to valleys (lower elevation areas) by means of wind redistribution, avalanches, and glacial motion may be considered as an equilibrator of the snow and ice storage system because it stimulates snow and ice ablation. In order to demonstrate this concept, a simple dynamic equilibrium model for regional to global scales is proposed and applied to the Pamirs. The interan...

Supply Chain Participant Behavior Research Based on Qualitative Simulation

The change of exterior environment and interaction of participants will influence the behavior of supply chain participants. The behavior of participants will present definite regularity and certainty in holistic level. The behavior rule of supply chain participants was researched by qualitative simulation method. Drawn from Group Dynamics theory in the science of Organizational Behavior, supply chain enterprises were classified into four categories which are core member, normal member, non-normal member and isolated member. The contents of Table 1 show the characteristic variables of various kinds of enterprises and their values. Figure 2 is used to represent the behavior causality among supply chain enterprises. The QSIM arithmetic and causal reasoning was used in qualitative simulation. The expression method of interaction between environment variable & decision variable and participants’ behavior was designed. The qualitative simulation rule and mechanism were given out. The behavior characteristics of different kinds of participants were educed by simulation. The main conclusions are as follows: Supply chain system is a dynamic equilibrium system. The interaction among supply chain enterprises and continuing to open up to the outside world are the main driving forces of supply chain system. For all enterprises, the active participations in supply chain cooperation have more advantages than the passive ones. The system role of supply chain has essential influence on non-normal member and isolated member. Simulation results in application show that the proposed method can be served as a virtual experiment tool for decision making in supply chain management.

Numerical simulation of the chaotic lateral vibrations of long rotating beams

The purpose of the present study is to investigate the global nonlinear dynamic behavior of long circular beams spinning about their longitudinal axes. Special attention is given to the stimulation of chaotic regimes. Contrary to the usual formulations which apply a fortiori energy methods, the dynamic equilibrium system is obtained using a Newtonian derivation procedure. The final mathematical model that governs the three dimensional nonlinear dynamics of the rotating beam is further elaborated in the time domain by employing a combination of finite difference solvers that rely on the second-order accurate Keller Box and Crank–Nicolson schemes. Several numerical tests have been performed assuming a drillstring structural model. The calculations show that the evolutions of the dynamic components that govern the kinematics of the concerned mechanical system are indeed chaotic. That feature was demonstrated in several different ways and in particular through Lyapunov exponents, phase space Poincaré maps and Power Spectral Densities of the time dependent variables.

Quantitative investigation on the stacking of metal ions induced by another metal ion based on moving substitution boundary electrophoresis

In this paper, a novel model for the stacking of metal ions via another metal ion was developed based on a dynamic equilibrium system (DES) composed of moving substitution boundary (MSB) and moving chelation boundary (MCB). With Cu2+, Co2+ and EDTA as an example, a substitution reaction took place between Cu2+ and [Co-EDTA]2−, and resulted in the formation of MSB, and Co2+ released from [Co-EDTA]2− reacted with EDTA, which resulted in the formation of MCB and [Co-EDTA]2−, the produced [Co-EDTA]2− reacted again with Cu2+. The reaction between Cu2+, [Co-EDTA]2−, and Co2+, EDTA were repeated. The concentration of Co2+ and [Co-EDTA]2− was stacked accompanying the formation of MSB and MCB until the above two reactions reached equilibrium. Relevant experiments were performed and the results indicated that: (1) Cu2+ can be used for the stacking of Co2+ and higher than 70-fold preconcentration of Co2+ was achieved in capillary electrophoresis (CE); (2) the concentration of Cu2+ had a key role in the stacking of Co2+, a higher Cu2+ concentration resulted in a better focusing efficiency; (3) the initial concentration and zone length (Linitial) of [Co-EDTA]2− were the major factors on enrichment. Furthermore, experiments based on MSB were performed with multi-metal ions (such as Cu2+, Co2+, Ni2+ and Pb2+), which demonstrated the potential application of the MSB-based technique for the separation and stacking of multi-metal ions.

Dynamic interaction of catenary risers with the seafloor

It is the purpose of this study to quantify the sea-bottom soil reaction effect on the dynamics of a Steel Catenary Riser by incorporating the soil reaction forces into the theoretical model of the dynamic equilibrium system. The calculations for the soil reaction forces have been performed quasi-statically, assuming specified embedment depths and trenching geometries. The plane stresses of the soil are determined with the aid of the commercial Geotechnical software, Phase2. Accordingly, the stresses are integrated around the arched riser–soil contact surface for the derivation of vertical soil reaction forces that resist to the penetration of the riser. These force-values are introduced in the nonlinear dynamic model as concentrated loads which are applied at the touchdown point (TDP). Several tests cases of top end harmonic excitations have been performed, aiming to investigate the effect of the TDP soil reaction on the various dynamic parameters which are responsible for fatigue damage.

The frequency of channel-forming discharges in a tributary of Upper Big Walnut Creek, Ohio

Understanding floodplain hydrology is necessary to interpret water quality and properly identify and predict the effectiveness of conservation practices in headwater watersheds. The goal of this study was to determine the frequency and magnitude of out-of-bank and channel-forming discharges in Sugar Creek, a tributary of the Upper Big Walnut Creek, in Ohio. To address this goal, a stream geomorphology study was conducted, measured discharge data at a downstream location were used to develop a calibrated discharge versus recurrence interval relationship, and the Hydrologic Engineering Center9s Hydrologic Modeling System (HEC-HMS) and River Analysis System (HEC-RAS) simulation models were used to develop out-of-bank discharge recurrence interval relationships for selected locations along Sugar Creek. Much of Sugar Creek was in dynamic equilibrium and had an extensive floodplain with entrenchment ratios ranging from 2 to 18. At the eight locations studied, two experienced bankfull or larger discharges an average of 12 times per year, with an approximate 0.2-year recurrence interval. Seventy-five percent of the locations experienced bankfull or larger discharges an average of at least 3 times per year, with an approximate 0.8-year recurrence interval. All of the locations experienced out-of-bank discharges an average of at least once per year, with the 2-year recurrence interval discharge. The annual out-of-bank discharges at each location ranged from 0.4% to 13% of the average annual flow volume. Based on the results, we recommended that research be conducted in the Sugar Creek Watershed to quantify the water quality benefits of a system in dynamic equilibrium and a well-attached, active floodplain.

Grigori Kuzmin and Stellar Dynamics

Abstract Grigori Kuzmin was a very gifted dynamicist and one of the towering figures in the distinguished history of the Tartu Observatory. He obtained a number of important results in relative isolation which were later rediscovered in the West. This work laid the foundation for further advances in the theory of stellar systems in dynamical equilibrium, thereby substantially increasing our understanding of galaxy dynamics.

Assessing channel-forming characteristics of an impacted headwater stream in Ohio, USA

Since the start of European settlement in Ohio the landscape has been greatly modified to accommodate anthropogenic land uses. This, in turn, has altered the hydrologic characteristics of many streams from those that are stable channel systems in dynamic equilibrium to those of modified incised channels that are more characteristic of anthropogenic influences. As stream restoration practices gain importance and prevalence there is a need to prioritize project funds based on the restoration potential of a stream. Regional curves that relate channel-forming geometry to drainage area, and applications of channel-forming discharge concepts, are tools that are used in making restoration and management decisions. Regional curves are usually developed for unmodified natural streams and/or gaged river systems and not for small, ungaged modified channels that are common throughout agricultural areas or mixed use watersheds. This study focuses on the development and potential usefulness of regional curves and channel-forming discharge concepts for Mac-o-chee Creek, a small, ungaged headwater stream system in Ohio. Results show that these approaches and a weight of evidence analysis could be useful in providing information for management and restoration decisions on these small stream systems as well as aiding in the assessment and modeling of trends within these streams with dynamic hydrologic conditions due to changes in land use/land cover.

A new test for the Galactic formation and evolution - prediction for the orbital eccentricity distribution of the halo stars

We present theoretical calculations for the differential distribution of stellar orbital eccentricity in a galaxy halo, assuming that the stars constitute a spherical, collisionless system in dynamical equilibrium with a dark matter halo. In order to define the eccentricity e of a halo star for given energy E and angular momentum L, we adopt two types of gravitational potential, such as an isochrone potential and a Navarro–Frenk–White potential, which could form two ends covering in-between any realistic potential of dark matter halo. Based on a distribution function of the form f(E, L) that allows constant anisotropy in velocity dispersions characterized by a parameter β, we find that the eccentricity distribution is a monotonically increasing function of e for the case of highly radially anisotropic velocity dispersions (β≳ 0.6), while showing a hump-like shape for the cases from radial through tangential velocity anisotropy (β≲ 0.6). We also find that when the velocity anisotropy agrees with that observed for the Milky Way halo stars (β≃ 0.5–0.7), a nearly linear eccentricity distribution of N(e) ∝e results at e≲ 0.7, largely independent of the potential adopted. Our theoretical eccentricity distribution would be a vital tool of examining how far out in the halo the dynamical equilibrium has been achieved, through comparison with kinematics of halo stars sampled at greater distances. Given that large surveys of the SEGUE and Gaia projects would be in progress, we discuss how our results would serve as a new guide in exploring the formation and evolution of the Milky Way halo.

In-cloud multiphase behaviour of acetone in the troposphere: Gas uptake, Henry’s law equilibrium and aqueous phase photooxidation

Acetone is ubiquitous in the troposphere. Several papers have focused in the past on its gas phase reactivity and its impact on tropospheric chemistry. However, acetone is also present in atmospheric water droplets where its behaviour is still relatively unknown. In this work, we present its gas/aqueous phase transfer and its aqueous phase photooxidation. The uptake coefficient of acetone on water droplets was measured between 268 and 281 K ( γ = 0.7 × 10 −2–1.4 × 10 −2), using the droplet train technique coupled to a mass spectrometer. The mass accommodation coefficient α (derived from γ) was found in the range (1.0–3.0 ± 0.25) × 10 −2. Henry’s law constant of acetone was directly measured between 283 and 298 K using a dynamic equilibrium system ( H (298K) = (29 ± 5) M atm −1), with the Van’t Hoff expression ln H ( T ) = (5100 ± 1100)/ T − (13.4 ± 3.9). A recommended value of H was suggested according to comparison with literature. The OH-oxidation of acetone in the aqueous phase was carried out at 298 K, under two different pH conditions: at pH = 2, and under unbuffered conditions. In both cases, the formation of methylglyoxal, formaldehyde, hydroxyacetone, acetic acid/acetate and formic acid/formate was observed. The formation of small amounts of four hydroperoxides was also detected, and one of them was identified as peroxyacetic acid. A drastic effect of pH was observed on the yields of formaldehyde, one hydroperoxide, and, (to a lesser extent) acetic acid/acetate. Based on the experimental observations, a chemical mechanism of OH-oxidation of acetone in the aqueous phase was proposed and discussed. Atmospheric implications of these findings were finally discussed.

PROPERTIES OF QUASI-RELAXED STELLAR SYSTEMS IN AN EXTERNAL TIDAL FIELD

In a previous paper, we have constructed a family of self-consistent triaxial models of quasi-relaxed stellar systems, shaped by the tidal field of the hosting galaxy, as an extension of the well-known spherical King models. For a given tidal field, the models are characterized by two physical scales (such as total mass and central velocity dispersion) and two dimensionless parameters (the concentration parameter and the tidal strength). The most significant departure from spherical symmetry occurs when the truncation radius of the corresponding spherical King model is of the order of the tidal radius, which, for a given tidal strength, is set by the maximum concentration value admitted. For such maximally extended (or "critical") models the outer boundary has a generally triaxial shape, given by the zero-velocity surface of the relevant Jacobi integral, which is basically independent of the concentration parameter. In turn, the external tidal field can give rise to significant global departures from spherical symmetry (as measured, for example, by the quadrupole of the mass distribution of the stellar system) only for low-concentration models, for which the allowed maximal value of the tidal strength can be relatively high. In this paper we describe in detail the intrinsic and the projected structure and kinematics of the models, covering the entire parameter space, from the case of sub-critical (characterized by "underfilling" of the relevant Roche volume) to that of critical models. The intrinsic properties can be a useful starting point for numerical simulations and other investigations that require initialization of a stellar system in dynamical equilibrium. The projected properties are a key step in the direction of a comparison with observed globular clusters and other candidate stellar systems.