995-22 The Effect of Perioperative Storage Solutions on the Long Term Vein Graft Function and Morphology

It has been shown that suboptimal preparation of a vein graft prior to its insertion results in immediate morphological and functional damage to the endothelial cells but not to the underlying smooth muscle cells. However. little is known if such perioperative injury to the vein grafts may influence the subsequent development of intimal hyperplasia and smooth muscle cell contractility. This study examines the influence of storage in saline or Ringer's lactate on the development of intimal hyperplasia and vasomotor function in experimental vein grafts. Twenty-six NM rabbits had a carotid vein bypass graft performed after the veins had been immersed (15 minutes) in either heparinized saline (Sal; n=13) or Ringer's lactate (RL; n=13) and each group was harvested after 28 days for either histology (n=8) or functional studies (n=5; four 5 mm rings/graft). Saline storage of the vein graft resulted in a 38% increase in the thickness of the intimal hyperplasia (113±2 vs. 83±μm, Sal vs. RL; mean±SEM, p<0.05) without a change in medial thickness (87±5 vs. 86±8μm, Sal vs. RL; p>0.05). There was no difference in the sensitivity to norepinephrine, serotonin and bradykinin between the two sets of vein grafts. The maximal contractile forces to serotonin and bradykinin were increased in the saline compared to Ringer's lactate stored vein grafts.SalineRinger'sp-valueNorepinephrine0.88±0.121.57±020<0.05Serotonin1.23±0.150.37±013<0.01Bradykinin2.08±0.110.52±007<0.01Values are the standardized maximal contractile force (maximal contraction/contraction to 60 mM KCI) expressed as mean±SEM.Saline storage of the vein graft results in the increased development of intimal hyperplasia with an overall enhanced contractility but without changes in agonist sensitivity. This study places further emphasis on the need for good perioperative care of the vein bypass graft because it results not only in the previously documented short term problems but also in long term structural and contractile changes which may contribute to decreased graft patency

1030-13 Alterations in Endothelial Cell Adenosine Receptors Mediate Endothelium-Dependent Vasoconstriction in Experimental Vein Grafts

Adenosine is a potent endogenous vasodilator which mediates its action through A1 and A2 receptor subtypes located on both vascular endothelial and vascular smooth muscle cells (SMC). Adenosine-mediated relaxation in vein grafts has not been examined. This study assesses the in vitro isometric tension responses to specific adenosine receptor agonists (A1: R-phenyl-isopropyl-adenosine and A2: CSG-21680; 10–9 to 10–4 M) of common carotid external jugular vein bypass grafts (VG) in New Zealand White rabbits. These responses were compared to those obtained in the extemal jugular vein (JV) and in the common carotid artery (CA). All vessels were precontracted with prostaglandin F2a (10–5 M). Endothelialized and de-endothelialized vessels were examined. The A1 mediated relaxation in JV was endothelium-independent, whereas A2 mediated relaxation was endothelium-dependent. In CA, A1 mediated relaxation was partially endothelium-dependent, while A2 mediated relaxation was endotheliumindependent. In VG, Al activation induced endothelium-dependent vasoconstriction. Endothelial denudation restored Al mediated relaxation, but reduced compared to that of JV (max. 19±9%). A2 relaxation in VG was endothelium-independent (max. 39±4%). Primary cultures of arterial and vein graft SMC expressed both A1 and A2 receptors on northern blot analysis. There was, however, a marked reduction in the A1 affinity of the SMC from the VG compared to the arterial SMC (40.9±1.3% arterial binding). This study, therefore, demonstrates that there is a substantial change in the adenosine mediated vasoreactivity in VG compared to JV, due to a change in endothelial A1 receptor mediated response from relaxation to constriction, coupled with a decreased affinity of the A1 receptors on the VG SMC. The adenosine responses of the VG are also different from CA. Therefore, the endothelial celis of VG appear to be unique, in that functionally they neither maintain a venous phenotype nor acquire an arterial phenotype in response to adenosine

Three Super-Earths Orbiting HD 7924

We report the discovery of two super-Earth mass planets orbiting the nearby K0.5 dwarf HD 7924 which was previously known to host one small planet. The new companions have masses of 7.9 and 6.4 M$_\oplus$, and orbital periods of 15.3 and 24.5 days. We perform a joint analysis of high-precision radial velocity data from Keck/HIRES and the new Automated Planet Finder Telescope (APF) to robustly detect three total planets in the system. We refine the ephemeris of the previously known planet using five years of new Keck data and high-cadence observations over the last 1.3 years with the APF. With this new ephemeris, we show that a previous transit search for the inner-most planet would have covered 70% of the predicted ingress or egress times. Photometric data collected over the last eight years using the Automated Photometric Telescope shows no evidence for transits of any of the planets, which would be detectable if the planets transit and their compositions are hydrogen-dominated. We detect a long-period signal that we interpret as the stellar magnetic activity cycle since it is strongly correlated with the Ca II H and K activity index. We also detect two additional short-period signals that we attribute to rotationally-modulated starspots and a one month alias. The high-cadence APF data help to distinguish between the true orbital periods and aliases caused by the window function of the Keck data. The planets orbiting HD 7924 are a local example of the compact, multi-planet systems that the Kepler Mission found in great abundance.Comment: Accepted to ApJ on 4/7/201

Constraints on the Atmospheric Circulation and Variability of the Eccentric Hot Jupiter XO-3b

We report secondary eclipse photometry of the hot Jupiter XO-3b in the 4.5~$\mu$m band taken with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We measure individual eclipse depths and center of eclipse times for a total of twelve secondary eclipses. We fit these data simultaneously with two transits observed in the same band in order to obtain a global best-fit secondary eclipse depth of $0.1580\pm 0.0036\%$ and a center of eclipse phase of $0.67004\pm 0.00013$. We assess the relative magnitude of variations in the dayside brightness of the planet by measuring the size of the residuals during ingress and egress from fitting the combined eclipse light curve with a uniform disk model and place an upper limit of 0.05$\%$. The new secondary eclipse observations extend the total baseline from one and a half years to nearly three years, allowing us to place an upper limit on the periastron precession rate of $2.9\times 10^{-3}$ degrees/day the tightest constraint to date on the periastron precession rate of a hot Jupiter. We use the new transit observations to calculate improved estimates for the system properties, including an updated orbital ephemeris. We also use the large number of secondary eclipses to obtain the most stringent limits to date on the orbit-to-orbit variability of an eccentric hot Jupiter and demonstrate the consistency of multiple-epoch Spitzer observations.Comment: 14 pages, 11 figures, published by Ap

3.6 and 4.5 μ\mum Spitzer{\it Spitzer} Phase Curves of the Highly-Irradiated Hot Jupiters WASP-19b and HAT-P-7b

We analyze full-orbit phase curve observations of the transiting hot Jupiters WASP-19b and HAT-P-7b at 3.6 and 4.5 $\mu$m obtained using the Spitzer Space Telescope. For WASP-19b, we measure secondary eclipse depths of $0.485\%\pm 0.024\%$ and $0.584\%\pm 0.029\%$ at 3.6 and 4.5 $\mu$m, which are consistent with a single blackbody with effective temperature $2372 \pm 60$ K. The measured 3.6 and 4.5 $\mu$m secondary eclipse depths for HAT-P-7b are $0.156\%\pm 0.009\%$ and $0.190\%\pm 0.006\%$, which are well-described by a single blackbody with effective temperature $2667\pm 57$ K. Comparing the phase curves to the predictions of one-dimensional and three-dimensional atmospheric models, we find that WASP-19b's dayside emission is consistent with a model atmosphere with no dayside thermal inversion and moderately efficient day-night circulation. We also detect an eastward-shifted hotspot, suggesting the presence of a superrotating equatorial jet. In contrast, HAT-P-7b's dayside emission suggests a dayside thermal inversion and relatively inefficient day-night circulation; no hotspot shift is detected. For both planets, these same models do not agree with the measured nightside emission. The discrepancies in the model-data comparisons for WASP-19b might be explained by high-altitude silicate clouds on the nightside and/or high atmospheric metallicity, while the very low 3.6 $\mu$m nightside planetary brightness for HAT-P-7b may be indicative of an enhanced global C/O ratio. We compute Bond albedos of 0 ($<0.08$ at $1\sigma$) and $0.38\pm 0.06$ for WASP-19b and HAT-P-7b, respectively. In the context of other planets with thermal phase curve measurements, we show that WASP-19b and HAT-P-7b fit the general trend of decreasing day-night heat recirculation with increasing irradiation.Comment: 22 pages, 29 figures, accepted by Ap

Spitzer Secondary Eclipse Observations of Five Cool Gas Giant Planets and Empirical Trends in Cool Planet Emission Spectra

In this work we present Spitzer 3.6 and 4.5 micron secondary eclipse observations of five new cool (<1200 K) transiting gas giant planets: HAT-P-19b, WASP-6b, WASP-10b, WASP-39b, and WASP-67b. We compare our measured eclipse depths to the predictions of a suite of atmosphere models and to eclipse depths for planets with previously published observations in order to constrain the temperature- and mass-dependent properties of gas giant planet atmospheres. We find that the dayside emission spectra of planets less massive than Jupiter require models with efficient circulation of energy to the night side and/or increased albedos, while those with masses greater than that of Jupiter are consistently best-matched by models with inefficient circulation and low albedos. At these relatively low temperatures we expect the atmospheric methane to CO ratio to vary as a function of metallicity, and we therefore use our observations of these planets to constrain their atmospheric metallicities. We find that the most massive planets have dayside emission spectra that are best-matched by solar metallicity atmosphere models, but we are not able to place strong constraints on metallicities of the smaller planets in our sample. Interestingly, we find that the ratio of the 3.6 and 4.5 micron brightness temperatures for these cool transiting planets is independent of planet temperature, and instead exhibits a tentative correlation with planet mass. If this trend can be confirmed, it would suggest that the shape of these planets' emission spectra depends primarily on their masses, consistent with the hypothesis that lower-mass planets are more likely to have metal-rich atmospheres.Comment: 16 pages, 14 figures, accepted for publication in Ap

The First Direct Detection of Kirkwood Transitions in Concentrated Aqueous Electrolytes using Small Angle X-ray Scattering

Ion-ion correlations, screening, and equilibrium bulk structure in various concentrated electrolytes are investigated using synchrotron small angle X-ray scattering (SAXS), theory, and molecular simulation. Utilizing SAXS measurements we provide estimates of the Kirkwood Transition (KT) for a variety of aqueous electrolytes (NaCl, CaCl$_2$, SrCl$_2$, and ErCl$_3$). The KT may be defined as the concentration above which the ion-ion correlations cease to decay exponentially with a single length scale given by the Debye length $\lambda_{\rm D}$ and develop an additional length scale, $d=2\pi/Q_0$ that reflects the formation of local domains of charge. Theoretical models of the KT have been known for decades for highly idealized models of electrolytes, but experimental verification of KT in real electrolytes has yet to be confirmed. Herein, we provide consistent theoretical and experimental estimates of both the inverse screening lengths $a_0$ and inverse domain size, $Q_0$ for the aforementioned electrolyte systems. Taken together, $a_0$ and $Q_0$ are known descriptors of the KT and provide a view into the complexity of ion-ion interaction beyond the well-accepted Debye-H\"{u}ckel limit. Our findings suggest a picture of interaction for real electrolytes that is more general than that found in idealized models that is manifest in the precise form of the non-local response function that we estimate through the interpretation of the experimental SAXS signal. Importantly, the additional complexity of describing ion-ion interaction of real electrolytes will implicate the short-range ion-ion interactions that can only be computed via molecular simulation and provide a quantitative approach to describe electrolyte phenomena beyond Debye-H\"{u}ckel theory.Comment: 3

Guide to Magellan image interpretation

An overview of Magellan Mission requirements, radar system characteristics, and methods of data collection is followed by a description of the image data, mosaic formats, areal coverage, resolution, and pixel DN-to-dB conversion. The availability and sources of image data are outlined. Applications of the altimeter data to estimate relief, Fresnel reflectivity, and surface slope, and the radiometer data to derive microwave emissivity are summarized and illustrated in conjunction with corresponding SAR image data. Same-side and opposite-side stereo images provide examples of parallax differences from which to measure relief with a lateral resolution many times greater than that of the altimeter. Basic radar interactions with geologic surfaces are discussed with respect to radar-imaging geometry, surface roughness, backscatter modeling, and dielectric constant. Techniques are described for interpreting the geomorphology and surface properties of surficial features, impact craters, tectonically deformed terrain, and volcanic landforms. The morphologic characteristics that distinguish impact craters from volcanic craters are defined. Criteria for discriminating extensional and compressional origins of tectonic features are discussed. Volcanic edifices, constructs, and lava channels are readily identified from their radar outlines in images. Geologic map units are identified on the basis of surface texture, image brightness, pattern, and morphology. Superposition, cross-cutting relations, and areal distribution of the units serve to elucidate the geologic history