Atomic-resolution electrochemistry with the atomic force microscope: copper deposition on gold

The atomic force microscope (AFM) was used to image an electrode surface at atomic resolution while the electrode was under potential control in a fluid electrolyte. A new level of subtlety was observed for each step of a complete electrochemical cycle that started with an Au(111) surface onto which bulk Cu was electrodeposited. The Cu was stripped down to an underpotential-deposited monolayer and finally returned to a bare Au(111) surface. The images revealed that the underpotential-deposited monolayer has different structures in different electrolytes. Specifically, for a perchloric acid electrolyte the Cu atoms are in a close-packed lattice with a spacing of 0.29 +/- 0.02 nanometer (nm). For a sulfate electrolyte they are in a more open lattice with a spacing of 0.49 +/- 0.02 nm. As the deposited Cu layer grew thicker, the Cu atoms converged to a (111)-oriented layer with a lattice spacing of 0.26 +/- 0.02 nm for both electrolytes. A terrace pattern was observed during dissolution of bulk Cu. Images were obtained of an atomically resolved Cu monolayer in one region and an atomically resolved Au substrate in another in which a 30 degrees rotation of the Cu monolayer lattice from the Au lattice is clearly visible.     

Transmutation and functional representation of heterogeneous landscapes

Models of local small-scale ecological processes can be used to describe related processes at larger spatial scales if the influences of increased scale and heterogeneity are carefully considered. In this paper we consider the changes in the functional representation of an ecological process that can occur as one moves from a local small-scale model to a model of the aggregate expression of that process for a larger spatial extent. We call these changes spatial transmutation. We specifically examine landscape heterogeneity as a cause of transmutation. Spatial transmutation as a consequence of landscape heterogeneity is a source of error in the prediction of aggregate landscape behavior from smaller scale models. However, we also demonstrate a procedure for taking advantage of spatial transmutation to develop appropriately scaled landscape functions. First a mathematical function describing the process of interest as a local function of local variables is defined. The spatial heterogeneity of the local variables is described by their statistical distribution in the landscape. The aggregate landscape expression of the local process is then predicted by calculating the expected value of the local function, explicitly integrating landscape heterogeneity. Monte Carlo simulation is used to repeat the local-to-landscape extrapolation for a variety of landscape patterns. Finally, the extrapolated landscape results are regressed on landscape variables to define response functions that explain a useful fraction of the total variation in landscape behavior. The response functions are hypotheses about the functional representation of the local process at the larger spatial scale.     

Canine von Willebrand's disease. A heterogeneous group of bleeding disorders

The term "von Willebrand's disease," refers to a group of inherited bleeding disorders, all of which are caused by a deficiency of the multimeric plasma glycoprotein, von Willebrand factor. The various forms of canine von Willebrand's disease can be categorized into one of three major types: in type I canine von Willebrand's disease, all sizes of von Willebrand factor multimers can be detected in the plasma; in type II canine von Willebrand's disease, only the smaller von Willebrand factor multimers are found in the plasma (larger multimers are absent); and in type III canine von Willebrand's disease, von Willebrand factor is completely absent from the plasma or present in only trace amounts. Von Willebrand's disease is common in dogs, but some forms of the disease are so mild that they are of questionable clinical significance.     

Estimating dispersibility of Acer,Fraxinus and Tilia in fragmented landscapes from patterns of seedling establishment

Relative dispersibility of Tilia americana L., Acer saccharum Marsh. and Fraxinus pennsylvanica Marsh, was inferred from the ratio among species-specific regression coefficients () computed from seedling density-distance plots. Density counts were made in spatially-uniform old fields adjacent to single seed sources or monotypic fencerows. Resultant seedling shadow curves approximate the negative exponential form expected for many seeds (log y=a–X). This basic curve shape fit species of differing dispersibility, dispersal under a range of wind directions and one-year-old or all-aged cohorts. The ratios of were 1:2.6:3.2 for Tilia, Acer and Fraxinus, respectively, in order of increasing dispersibility. Vegetation patches isolated from seed sources by several hundred meters or more should have extremely low input of seeds, especially Tilia and Acer.The finding that Fraxinus disperses farther than Acer was unexpected, since the samaras of the former have faster terminal velocities. The relationship can be explained by better performance of Fraxinus samaras in the stronger winds experienced by trees in open landscapes, poorer formation of the samara abscission layer, and release of samaras following leaf abscission and during the winter when winds are the strongest. Both the samara plan and dispersal phenology need to be considered in estimating relative dispersibility among species.     

Comparative studies of strains of infectious bovine rhinotracheitis virus isolated from latently infected calves

Three strains (479 C, 778 TL, 982 LE) of infectious bovine rhinotracheitis (IBR) virus isolated from latently infected calves were compared with the prototype strain of IBR virus (LA strain) in studies which included restriction endonuclease analysis, experimental infection, and reciprocal cross protection tests in cattle. From the restriction endonuclease analysis it appeared that the 3 "latent" viruses were derived from the same isolate, and that it differed slightly from the LA strain. However, latency does not seem to have affected the pathogenicity or the immunogenicity of the virus. This is demonstrated by the identical clinical and virologic response of calves subjected to experimental infection with the various strains under study, and by the finding that when the LA strain and a "latent" strain (982 LE) were tested in cross protection tests in cattle, they proved to be mutually protective.     

Multiple cytopenias associated with monocytic proliferation in a dog

An unusual combination of blood cytopenias and monocytic proliferation was observed in a dog. Initial hematologic findings included severe thrombocytopenia, neutropenia, mild nonregenerative anemia and apparently normal bone marrow. Subsequently, a severe persistent monocytosis developed and the bone marrow became populated with monocytes and cytophagic macrophages. Splenomegaly was due to reticuloendothelial hyperplasia and extramedultary hematopoiesis. Treatment consisted of splenectomy and azathioprine but the response was poor and the dog was euthanized. Postmortem examination revealed a hypocellular bone marrow which contained moderate numbers of monocytes and plasma cells. Neoplastic proliferation was absent in visceral organs. No definite diagnosis was established; chronic blood cell consumption, perhaps immune-mediated, may have been responsible for the extensive reticuloendothelial hyperplasia and cytophagia.     

Venus: detailed mapping of maxwell montes region

From October 1983 to July 1984, the north hemisphere of Venus, from latitude 30 degrees to latitude 90 degrees , was mapped by means of the radar imagers and altimeters of the spacecraft Venera 15 and Venera 16. This report presents the results of the radar mapping of the Maxwell Montes region, one of the most interesting features of Venus' surface. A radar mosaic map and contour map have been compiled.     

Changing climate: geothermal evidence from permafrost in the alaskan arctic

Temperature profiles measured in permafrost in northernmost Alaska usually have anomalous curvature in the upper 100 meters or so. When analyzed by heat-conduction theory, the profiles indicate a variable but widespread secular warming of the permafrost surface, generally in the range of 2 to 4 Celsius degrees during the last few decades to a century. Although details of the climatic change cannot be resolved with existing data, there is little doubt of its general magnitude and timing; alternative explanations are limited by the fact that heat transfer in cold permafrost is exclusively by conduction. Since models of greenhouse warming predict climatic change will be greatest in the Arctic and might already be in progress, it is prudent to attempt to understand the rapidly changing thermal regime in this region.