Abstract. Pseudoproxy experiments (PPEs) have become an important framework for evaluating paleoclimate reconstruction methods. Most existing PPE studies assume constant proxy availability through time and uniform proxy quality across the pseudoproxy network. Real multiproxy networks are, however, marked by pronounced disparities in proxy quality, and a steep decline in proxy availability back in time, either of which may have large effects on reconstruction skill. A suite of PPEs constructed from a millennium-length general circulation model (GCM) simulation is thus designed to mimic these various real-world characteristics. The new pseudoproxy network is used to evaluate four climate field reconstruction (CFR) techniques: truncated total least squares embedded within the regularized EM (expectation-maximization) algorithm (RegEM-TTLS), the Mann et al. (2009) implementation of RegEM-TTLS (M09), canonical correlation analysis (CCA), and Gaussian graphical models embedded within RegEM (GraphEM). Each method's risk properties are also assessed via a 100-member noise ensemble. Contrary to expectation, it is found that reconstruction skill does not vary monotonically with proxy availability, but also is a function of the type and amplitude of climate variability (forced events vs. internal variability). The use of realistic spatiotemporal pseudoproxy characteristics also exposes large inter-method differences. Despite the comparable fidelity in reconstructing the global mean temperature, spatial skill varies considerably between CFR techniques. Both GraphEM and CCA efficiently exploit teleconnections, and produce consistent reconstructions across the ensemble. RegEM-TTLS and M09 appear advantageous for reconstructions on highly noisy data, but are subject to larger stochastic variations across different realizations of pseudoproxy noise. Results collectively highlight the importance of designing realistic pseudoproxy networks and implementing multiple noise realizations of PPEs. The results also underscore the difficulty in finding the proper bias-variance tradeoff for jointly optimizing the spatial skill of CFRs and the fidelity of the global mean reconstructions.

Cardiac glycosides exert a positive inotropic effect by inhibiting sodium pump (Na,K-ATPase) activity, decreasing the driving force for Na ϩ -Ca ϩϩ exchange, and increasing cellular content and release of Ca ϩϩ during depolarization. Since the inotropic response will be a function of the level of expression of sodium pumps, which are ␣␤ heterodimers, and of Na ϩ -Ca ϩϩ exchangers, this study aimed to determine the regional pattern of expression of these transporters in the heart. Immunoblot assays of homogenate from atria, ventricles, and septa of 14 nonfailing human hearts established expression of Na,K-ATPase ␣ 1, ␣ 2, ␣ 3, ␤ 1, and Na ϩ -Ca ϩϩ exchangers in all regions. Na,K-ATPase ␤ 2 expression is negligible, indicating that the human cardiac glycoside receptors are ␣ 1 ␤ 1,, ␣ 2 ␤ 1, and ␣ 3 ␤ 1. ␣ 3, ␤ 1, sodium pump activity, and Na ϩ -Ca ϩϩ exchanger levels were 30-50% lower in atria compared to ventricles and/or septum; differences between ventricles and septum were insignificant. Functionally, the EC 50 of the sodium channel activator BDF 9148 to increase force of contraction was lower in atria than ventricle muscle strips (0.36 vs. 1.54 M). These results define the distribution of the cardiac glycoside receptor isoforms in the human heart and they demonstrate that atria have fewer sodium pumps, fewer Na ϩ -Ca ϩϩ exchangers, and enhanced sensitivity to inotropic stimulation compared to ventricles. ( J. Clin. Invest. 1996. 98:1650-1658.)

No abstract

The adsorption of nitromethane (CH3NO2 and CD3NO2) and d 3-methyl nitrite (CD3ONO) on Au(111) was studied by temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). These molecules are only weakly adsorbed on Au(111), and adsorption is completely reversible in both cases. Adsorbed CH3NO2 and CD3ONO in the monolayer each give rise to one thermal desorption peak in TPD with desorption activation energies of 10.5 and 8 kcal/mol, respectively. These desorption energies are close to the values for the heats of adsorption of these molecules, since there is no appreciable activation energy for molecular adsorption. HREELS confirms weak, molecular adsorption in the monolayer for both molecules. Furthermore, nitromethane is bonded on Au(111) in an upright, strongly tilted geometry, suggesting a monodentate coordination to the surface. Methyl nitrite adsorbs on Au(111) with the ONO group in a flat-lying geometry, with evidence for both cis and trans forms. The Au(111) surface does not sufficiently activate nitromethane and methyl nitrite for dissociation or isomerization (CH3NO2 ↔ CH3ONO) to occur under UHV conditions. Thus the activation energies for dissociation and isomerization of nitromethane on Au(111) exceed 10.5 kcal/mol.

Index Terms-GaN, high electron-mobility transistor (HEMT), -band, microwave noise, microwave power.