Solvent Azeotropes in Art Conservation

Solvent mixtures are often fine-tuned by art conservators for the difficult tasks of safely removing yellowed varnishes and obfuscating dirt from oil paintings. These two goals are often loosely termed “picture cleaning.” Concern has been raised over the impact of differential evaporation rates for solvents in the cleaning mixture. Differential evaporation can lead to changes in the mixture’s potency over time and potentially lead to solvent mixtures on the surface of the artwork having solubility characteristics deleterious to artists’ oil paints. Azeotropic mixtures of solvents have been proposed as an alternative for maintaining consistent solvent composition. Azeotropes are specific mixtures of two or more solvents that behave as a single solvent and maintain a constant composition at their boiling point. The azeotropes that have appeared in the art conservation literature are taken from tables of azeotropic compositions in the CRC Handbook given at their boiling point. This research examines whether these solvent blends, in particular a hexane/isopropanol combination found to be an effective cleaner in the treatment of painted royal sleighs at the Palace of Versailles, in fact behave azeotropically under room temperature evaporation conditions. For the first time, the actual evaporation behavior of this purported azeotropic mixture will be explored in depth. A range of hexane/isopropanol mixtures around the boiling point azeotrope composition have been assessed for their room temperature vapor pressure and evaporation weight loss kinetics. Aliquots of the evaporating solutions are also being analyzed chemically using gas chromatography of both the liquid phase and the vapor phase in the headspace. This research aims to provide conservators information on the evaporation of purportedly azeotropic solvent blends and to suggest new approaches to the cleaning of oil paintings

Warm Molecular Gas in M51: Mapping the Excitation Temperature and Mass of H_2 with the Spitzer Infrared Spectrograph

We have mapped the warm molecular gas traced by the H_2 S(0) - H_2 S(5) pure rotational mid-infrared emission lines over a radial strip across the nucleus and disk of M51 (NGC 5194) using the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. The six H_2 lines have markedly different emission distributions. We obtained the H_2 temperature and surface density distributions by assuming a two temperature model: a warm (T = 100 - 300 K) phase traced by the low J (S(0) - S(2)) lines and a hot phase (T = 400 - 1000 K) traced by the high J (S(2) - S(5)) lines. The lowest molecular gas temperatures are found within the spiral arms (T ~ 155 K), while the highest temperatures are found in the inter-arm regions (T > 700 K). The warm gas surface density reaches a maximum of 11 M_sun/pc^2 in the northwestern spiral arm, whereas the hot gas surface density peaks at 0.24 M_sun/pc^2 at the nucleus. The spatial offset between the peaks in the warm and hot phases and the differences in the distributions of the H_2 line emission suggest that the warm phase is mostly produced by UV photons in star forming regions while the hot phase is mostly produced by shocks or X-rays associated with nuclear activity. The warm H_2 is found in the dust lanes of M51, spatially offset from the brightest HII regions. The warm H_2 is generally spatially coincident with the cold molecular gas traced by CO (J = 1 - 0) emission, consistent with excitation of the warm phase in dense photodissociation regions (PDRs). In contrast, the hot H_2 is most prominent in the nuclear region. Here, over a 0.5 kpc radius around the nucleus of M51, the hot H_2 coincides with [O IV](25.89 micron) and X-ray emission indicating that shocks and/or X-rays are responsible for exciting this phase

Resolving \u3ci\u3eBovine viral diarrhea virus\u3c/i\u3e subtypes from persistently infected U.S. beef calves with complete genome sequence

Bovine viral diarrhea virus (BVDV) is classified into 2 genotypes, BVDV-1 and BVDV-2, each of which contains distinct subtypes with genetic and antigenic variation. To effectively control BVDV by vaccination, it is important to know which subtypes of the virus are circulating and how their prevalence is changing over time. Accordingly, the purpose of our study was to estimate the current prevalence and diversity of BVDV subtypes from persistently infected (PI) beef calves in the central United States. Phylogenetic analysis of the 5′-UTR (5′ untranslated region) for 119 virus strains revealed that a majority (82%) belonged to genotype 1b, and the remaining strains were distributed between genotypes 1a (9%) and 2 (8%); however, BVDV-2 subtypes could not be confidently resolved. Therefore, to better define the variability of U.S. BVDV isolates and further investigate the division of BVDV-2 isolates into subtypes, complete genome sequences were obtained for these isolates as well as representatives of BVDV-1a and -1b. Phylogenetic analyses of the complete coding sequence provided more conclusive genetic classification and revealed that U.S. BVDV-2 isolates belong to at least 3 distinct genetic groups that are statistically supported by both complete and individual coding gene analyses. These results show that a more complex set of BVDV-2 subtypes has been circulating in this region than was previously thought

Resolving \u3ci\u3eBovine viral diarrhea virus\u3c/i\u3e subtypes from persistently infected U.S. beef calves with complete genome sequence

Bovine viral diarrhea virus (BVDV) is classified into 2 genotypes, BVDV-1 and BVDV-2, each of which contains distinct subtypes with genetic and antigenic variation. To effectively control BVDV by vaccination, it is important to know which subtypes of the virus are circulating and how their prevalence is changing over time. Accordingly, the purpose of our study was to estimate the current prevalence and diversity of BVDV subtypes from persistently infected (PI) beef calves in the central United States. Phylogenetic analysis of the 5′-UTR (5′ untranslated region) for 119 virus strains revealed that a majority (82%) belonged to genotype 1b, and the remaining strains were distributed between genotypes 1a (9%) and 2 (8%); however, BVDV-2 subtypes could not be confidently resolved. Therefore, to better define the variability of U.S. BVDV isolates and further investigate the division of BVDV-2 isolates into subtypes, complete genome sequences were obtained for these isolates as well as representatives of BVDV-1a and -1b. Phylogenetic analyses of the complete coding sequence provided more conclusive genetic classification and revealed that U.S. BVDV-2 isolates belong to at least 3 distinct genetic groups that are statistically supported by both complete and individual coding gene analyses. These results show that a more complex set of BVDV-2 subtypes has been circulating in this region than was previously thought

Quantification of bedform dynamics and bedload sediment flux in sandy braided rivers from airborne and satellite imagery

Images from specially‐commissioned aeroplane sorties (manned aerial vehicle, MAV), repeat unmanned aerial vehicle (UAV) surveys, and Planet CubeSat satellites are used to quantify dune and bar dynamics in the sandy braided South Saskatchewan River, Canada. Structure‐from‐Motion (SfM) techniques and application of a depth‐brightness model are used to produce a series of Digital Surface Models (DSMs) at low and near‐bankfull flows. A number of technical and image processing challenges are described that arise from the application of SfM in dry and submerged environments. A model for best practice is presented and analysis suggests a depth‐brightness model approach can represent the different scales of bedforms present in sandy braided rivers with low‐turbidity and shallow (< 2 m deep) water. The aerial imagery is used to quantify the spatial distribution of unit bar and dune migration rate in an 18 km reach and three ~1 km long reaches respectively. Dune and unit bar migration rates are highly variable in response to local variations in planform morphology. Sediment transport rates for dunes and unit bars, obtained by integrating migration rates (from UAV) with the volume of sediment moved (from DSMs using MAV imagery) show near‐equivalence in sediment flux. Hence, reach‐based sediment transport rate estimates can be derived from unit bar data alone. Moreover, it is shown that reasonable estimates of sediment transport rate can be made using just unit bar migration rates as measured from 2D imagery, including from satellite images, so long as informed assumptions are made regarding average bar shape and height. With recent availability of frequent, repeat satellite imagery, and the ease of undertaking repeat MAV and UAV surveys, for the first time, it may be possible to provide global estimates of bedload sediment flux for large or inaccessible low‐turbidity rivers that currently have sparse information on bedload sediment transport rates

The 1-1000 micron SEDs of far-infrared galaxies

Galaxies selected at 170um by the ISO FIRBACK survey represent the brightest \~10% of the Cosmic Infrared Background. Examining their nature in detail is therefore crucial for constraining models of galaxy evolution. Here we combine Spitzer archival data with previous near-IR, far-IR, and sub-mm observations of a representative sample of 22 FIRBACK galaxies spanning three orders of magnitude in infrared luminosity. We fit a flexible, multi-component, empirical SED model of star-forming galaxies designed to model the entire ~1-1000um wavelength range. The fits are performed with a Markov Chain Monte Carlo (MCMC) approach, allowing for meaningful uncertainties to be derived. This approach also highlights degeneracies such as between Td and beta, which we discuss in detail. From these fits and standard relations we derive: L_IR, L_PAH, SFR, tau_V, M_star, M_dust, Td, and beta. We look at a variety of correlations between these and combinations thereof in order to examine the physical nature of these galaxies. Our conclusions are supplemented by morphological examination of the sources, and comparison with local samples. We find the bulk of our sample to be consistent with fairly standard size and mass disk galaxies with somewhat enhanced star-formation relative to local spirals, but likely not bona fide starbursts. A few higher-z LIGs and ULIGs are also present, but contrary to expectation, they are weak mid-IR emitters and overall are consistent with star-formation over an extended cold region rather than concentrated in the nuclear regions. We discuss the implications of this study for understanding populations detected at other wavelengths, such as the bright 850um SCUBA sources or the faint Spitzer 24um sources.Comment: 19 pages, 20 figures, accepted for publication in MNRA

Paschen-alpha Emission in the Gravitationally Lensed Galaxy SMM J163554.2+661225

We report the detection of the Paschen-alpha emission line in the z=2.515 galaxy SMM J163554.2+661225 using Spitzer spectroscopy. SMM J163554.2+661225 is a sub-millimeter-selected infrared (IR)-luminous galaxy maintaining a high star-formation rate (SFR), with no evidence of an AGN from optical or infrared spectroscopy, nor X-ray emission. This galaxy is lensed gravitationally by the cluster Abell 2218, making it accessible to Spitzer spectroscopy. Correcting for nebular extinction derived from the H-alpha and Pa-alpha lines, the dust-corrected luminosity is L(Pa-alpha) = (2.57+/-0.43) x 10^43 erg s^-1, which corresponds to an ionization rate, Q = (1.6+/-0.3) x 10^55 photons s^-1. The instantaneous SFR is 171+/-28 solar masses per year, assuming a Salpeter-like initial mass function. The total IR luminosity derived using 70, 450, and 850 micron data is L(IR) = (5-10) x 10^11 solar luminosities, corrected for gravitational lensing. This corresponds to a SFR=90-180 solar masses per year, where the upper range is consistent with that derived from the Paschen-alpha luminosity. While the L(8 micron) / L(Pa-alpha) ratio is consistent with the extrapolated relation observed in local galaxies and star-forming regions, the rest-frame 24 micron luminosity is significantly lower with respect to local galaxies of comparable Paschen-alpha luminosity. Thus, SMM J163554.2+661225 arguably lacks a warmer dust component (T ~ 70 K), which is associated with deeply embedded star formation, and which contrasts with local galaxies with comparable SFRs. Rather, the starburst is consistent with star-forming local galaxies with intrinsic luminosities, L(IR) ~ 10^10 solar luminosities, but "scaled-up" by a factor of 10-100.Comment: Published in the Astrophysical Journal. 14 pages in emulateapj format, 9 figures (many in color

Synthesis and evaluation of new polynuclear organometallic Ru(II), Rh(III) and Ir(III) pyridyl ester complexes as in vitro antiparasitic and antitumor agents

New polynuclear organometallic Platinum Group Metal (PGM) complexes containing di- and tripyridyl ester ligands have been synthesised and characterised using analytical and spectroscopic techniques including H-1, C-13 NMR and infrared spectroscopy. Reaction of these polypyridyl ester ligands with either [Ru(p-cymene)Cl-2](2), [Rh(C5Me5)Cl-2](2) or [Ir(C5Me5)Cl-2](2) dimers yielded the corresponding di- or trinuclear organometallic complexes. The polyaromatic ester ligands act as monodentate donors to each metal centre and this coordination mode was confirmed upon elucidation of the molecular structures for two of the dinuclear complexes. The di- and trinuclear PGM complexes synthesized were evaluated for inhibitory effects on the human protozoal parasites Plasmodium falciparum strain NF54 (chloroquine sensitive), Trichomonas vaginalis strain G3 and the human ovarian cancer cell lines, A2780 (cisplatin-sensitive) and A2780cisR (cisplatin-resistant) cell lines. All of the complexes were observed to have moderate to high antiplasmodial activities and the compounds with the best activities were evaluated for their ability to inhibit formation of synthetic hemozoin in a cell free medium. The in vitro antitumor evaluation of these complexes revealed that the trinuclear pyridyl ester complexes demonstrated moderate activities against the two tumor cell lines and were also less toxic to model non-tumorous cells

Probing the Star Formation History and Initial Mass Function of the z~2.5 Lensed Galaxy SMM J163554.2+661225 with Herschel

We present the analysis of Herschel SPIRE far-infrared (FIR) observations of the z = 2.515 lensed galaxy SMM J163554.2+661225. Combining new 250, 350, and 500 micron observations with existing data, we make an improved fit to the FIR spectral energy distribution (SED) of this galaxy. We find a total infrared (IR) luminosity of L(8--1000 micron) = 6.9 +/- 0.6x10^11 Lsol; a factor of 3 more precise over previous L_IR estimates for this galaxy, and one of the most accurate measurements for any galaxy at these redshifts. This FIR luminosity implies an unlensed star formation rate (SFR) for this galaxy of 119 +/- 10 Msol per yr, which is a factor of 1.9 +/- 0.35 lower than the SFR derived from the nebular Pa-alpha emission line (a 2.5-sigma discrepancy). Both SFR indicators assume identical Salpeter initial mass functions (IMF) with slope Gamma=2.35 over a mass range of 0.1 - 100 Msol, thus this discrepancy suggests that more ionizing photons may be necessary to account for the higher Pa-alpha-derived SFR. We examine a number of scenarios and find that the observations can be explained with a varying star formation history (SFH) due to an increasing star formation rate (SFR), paired with a slight flattening of the IMF. If the SFR is constant in time, then larger changes need to be made to the IMF by either increasing the upper-mass cutoff to ~ 200 Msol, or a flattening of the IMF slope to 1.9 +/- 0.15, or a combination of the two. These scenarios result in up to double the number of stars with masses above 20 Msol, which produce the requisite increase in ionizing photons over a Salpeter IMF with a constant SFH.Comment: 9 pages, 4 figures, 1 table; Accepted for publication in the Astrophysical Journa

Global Physical Conditions of the Interstellar Medium in Nearby Galaxies

Far-infrared spectra (43-197um) of 34 nearby galaxies obtained by the Long Wavelength Spectrometer (LWS) aboard the Infrared Space Observatory (ISO) were analyzed to investigate the general properties of interstellar matter in galaxies. The line fluxes of [CII]158um and [NII]122um relative to the total far-infrared flux (FIR) decrease as the far-infrared color becomes bluer, while the ratio of the [OI]63um flux to FIR does not show a systematic trend with the color. The [OIII]88um to FIR ratio shows a large scatter with a weak trend of increase with the color. We estimate the physical conditions of photodissociation regions (PDRs) in the sample galaxies, such as the far-ultraviolet radiation field intensity Go and the gas density n by assuming that all the observed [OI]63um and far-infrared continuum emissions come from PDRs. The present analysis suggests that the decrease in [CII]158um/FIR with the far-infrared color may not be accounted for by the decrease in the photoelectric heating efficiency owing to the increase in positive charges of dust grains because a measure of the efficiency, Go/n, is found to stay constant with the far-infrared color. Instead the decrease can be interpreted in terms of either the increase in the collisional de-excitation of the [CII] transition due to the increase in the gas density or the decrease in the ionized component relative to the far-infrared intensity suggested by the decrease in [NII]122um/FIR. Based on the present analysis, we derive average relations of the far-infrared color with Go and n in galaxies, which can be applied to the investigation of interstellar matter in distant galaxies.Comment: to apear in A&