Analysis of the symbiotic star AG Pegasi

High and low dispersion IUE data are analyzed in conjunction with coincident ground based spectrophotometric scans and supplementary infrared photometry of the symbiotic object AG Pegasi. The IUE observations yield an improved value of E(B-V) = 0.12. The two stellar components are easily recognized in the spectra. The cool component may be an M1.7 III star and the hot component appears to have T (sub eff) of approximately 30000 K. The emission lines observed in the ultraviolet indicate two or three distince emitting regions. Nebular component ultraviolet intercombination lines suggest an electron density of several times 10 billion/cu cm

Delivery of a Fatty Acid Signal Via RTIL for Biofilm Dispersion

A number of proposed applications for ionic liquids involve ionic liquid/water interfaces, such as, chemical separations or drug delivery systems. Therefore, an understanding of the solubility and micellar behavior of ionic liquids in an aqueous environment is critical fundamental knowledge. The long term goal of our study was ionic liquids for delivery of biological active agents; therefore, we chose the anion, bis(trifluoromethanesulfonyl)imide (Tf2N) since it promotes water stability and forms water immiscible RTILs. The study then paired the Tf2N-anion with three different classes of cations. By adding apolar substituents (-CH2-) to the cation, the size of the molecule increases in each RTIL class, rendering the RTIL less soluble in the water phase. The three classes of RTILs examined were 1-Cn-3-methylimidazolum (Rmim), Cn-trimethylammonium (CTA), and branched ammonium (BAM), with the “Cn” representing an alkyl functional group (propyl, butyl, etc.). For industrial use, CTAs are attractive, since they can be synthesized from inexpensive ammonium surfactants. However, large CTAs (twelve carbon chain and higher) are solids at ambient conditions. In contrast, BAMs have larger compounds that remain in the liquid state at ambient conditions. Nevertheless, each class has potential as a delivery agent by meeting the aforementioned criterion – namely, water immiscible and water stable at ambient temperatures. We used Total Organic Carbon (TOC) analysis to determine the RTIL content in water that is in equilibrium with the tested RTILs. Surface tension measurements of the RTIL containing water determined if RTIL micelles existed in the RTIL saturated water. We used LFER (Linear Free Energy Relationship) semi-empirical models to correlate the RTIL water solubility to the molecular size and structure of the RTIL cation. Combining the LFER results with surface tension measurements and thermodynamic calculations of sub-cooled RTIL fugacities, allowed us to determine that micelle formation is not significant for the tested RTILs with molar volumes less than 350 cm3/mol. We tested a total of 15 different RTILs with the water solubilities ranging from 10-2 to 10-4 moles-RTIL/L-water. Based on the water solubilities, the proposed RTILs are [N(10)111][Tf2N], [N(10)Me2(iPr)][Tf2N], and [C(6)MIM][Tf2N] for delivery of the signal cis-2-decenoic acid for biofilm dispersion

Responsive Management: Municipal Leadership for an Aging Population

This article focuses on the responsive management of municipal leadership by identifying organizational and community values that affect age friendly policy making. The data comes from a sample of 1050 cities extracted from a national list of cities identified as place geography on the U.S. census list of geographies. The web-based questionnaire explored policy choices of 331 respondents in the areas of mobility, housing, the built environment, and public service delivery administered between May and August 2016. The institutionalization of the needs of an aging population in city management principles results in high levels of age friendly policy action by cities. Public advocacy on aging issues enhances the impact on local policy-making. Safeguarding of public interest through city management suggests municipalities may adjust procedurally to respond to the needs of an aging population. Public managers may find opportunities to facilitate increased policy action and services to support a growing older adult population. There are implications for older people to age in place when their community lacks municipal leadership on aging in place policies and older people have limited voice on aging issues

The Potential Energy Landscape and Mechanisms of Diffusion in Liquids

The mechanism of diffusion in supercooled liquids is investigated from the potential energy landscape point of view, with emphasis on the crossover from high- to low-T dynamics. Molecular dynamics simulations with a time dependent mapping to the associated local mininum or inherent structure (IS) are performed on unit-density Lennard-Jones (LJ). New dynamical quantities introduced include r2_{is}(t), the mean-square displacement (MSD) within a basin of attraction of an IS, R2(t), the MSD of the IS itself, and g_{loc}(t) the mean waiting time in a cooperative region. At intermediate T, r2_{is}(t) posesses an interval of linear t-dependence allowing calculation of an intrabasin diffusion constant D_{is}. Near T_{c} diffusion is intrabasin dominated with D = D_{is}. Below T_{c} the local waiting time tau_{loc} exceeds the time, tau_{pl}, needed for the system to explore the basin, indicating the action of barriers. The distinction between motion among the IS below T_{c} and saddle, or border dynamics above T_{c} is discussed.Comment: submitted to pr

Electron-Acoustic Phonon Energy Loss Rate in Multi-Component Electron Systems with Symmetric and Asymmetric Coupling Constants

We consider electron-phonon (\textit{e-ph}) energy loss rate in 3D and 2D multi-component electron systems in semiconductors. We allow general asymmetry in the \textit{e-ph} coupling constants (matrix elements), i.e., we allow that the coupling depends on the electron sub-system index. We derive a multi-component \textit{e-ph}power loss formula, which takes into account the asymmetric coupling and links the total \textit{e-ph} energy loss rate to the density response matrix of the total electron system. We write the density response matrix within mean field approximation, which leads to coexistence of\ symmetric energy loss rate $F_{S}(T)$ and asymmetric energy loss rate $F_{A}(T)$ with total energy loss rate $F(T)=F_{S}(T)+F_{A}(T)$ at temperature $T$. The symmetric component F_{S}(T) $is equivalent to the conventional single-sub-system energy loss rate in the literature, and in the Bloch-Gr\"{u}neisen limit we reproduce a set of well-known power laws$F_{S}(T)\propto T^{n_{S}}$, where the prefactor and power$n_{S}$depend on electron system dimensionality and electron mean free path. For$F_{A}(T)$we produce a new set of power laws F_{A}(T)\propto T^{n_{A}}$. Screening strongly reduces the symmetric coupling, but the asymmetric coupling is unscreened, provided that the inter-sub-system Coulomb interactions are strong. The lack of screening enhances $F_{A}(T)$ and the total energy loss rate $F(T)$. Especially, in the strong screening limit we find $F_{A}(T)\gg F_{S}(T)$. A canonical example of strongly asymmetric \textit{e-ph} matrix elements is the deformation potential coupling in many-valley semiconductors.Comment: v2: Typos corrected. Some notations changed. Section III.C is embedded in Section III.B. Paper accepted to PR

Inherent-Structure Dynamics and Diffusion in Liquids

The self-diffusion constant D is expressed in terms of transitions among the local minima of the potential (inherent structure, IS) and their correlations. The formulae are evaluated and tested against simulation in the supercooled, unit-density Lennard-Jones liquid. The approximation of uncorrelated IS-transition (IST) vectors, D_{0}, greatly exceeds D in the upper temperature range, but merges with simulation at reduced T ~ 0.50. Since uncorrelated IST are associated with a hopping mechanism, the condition D ~ D_{0} provides a new way to identify the crossover to hopping. The results suggest that theories of diffusion in deeply supercooled liquids may be based on weakly correlated IST.Comment: submitted to PR

Instantaneous Normal Mode analysis of liquid HF

We present an Instantaneous Normal Modes analysis of liquid HF aimed to clarify the origin of peculiar dynamical properties which are supposed to stem from the arrangement of molecules in linear hydrogen-bonded network. The present study shows that this approach is an unique tool for the understanding of the spectral features revealed in the analysis of both single molecule and collective quantities. For the system under investigation we demonstrate the relevance of hydrogen-bonding ``stretching'' and fast librational motion in the interpretation of these features.Comment: REVTeX, 7 pages, 5 eps figures included. Minor changes in the text and in a figure. Accepted for publication in Phys. Rev. Let