Metathesis of Alkanes Catalyzed by Silica-Supported Transition Metal Hydrides

The silica-supported transition metal hydrides (=Si-O-Si=)(=Si-O-)2Ta-H and (=Si-O-)xM-H (M, chromium or tungsten) catalyze the metathesis reaction of linear or branched alkanes into the next higher and lower alkanes at moderate temperature (25degrees to 200degreesC). With (=Si-O-Si=)(=Si-O-)2Ta-H, ethane was transformed at room temperature into an equimolar mixture of propane and methane. Higher and lower homologs were obtained from propane, butane, and pentane as well as from branched alkanes such as isobutane and isopentane. The mechanism of the step leading to carbon-carbon bond cleavage and formation likely involves a four-centered transition state between a tantalum-alkyl intermediate and a carbon-carbon final sigma-bond of a second molecule of alkane.     

Spatial Variability of Turbulent Mixing in the Abyssal Ocean

Ocean microstructure data show that turbulent mixing in the deep Brazil Basin of the South Atlantic Ocean is weak at all depths above smooth abyssal plains and the South American Continental Rise. The diapycnal diffusivity there was estimated to be less than or approximately equal to 0.1 x 10(-4) meters squared per second. In contrast, mixing rates are large throughout the water column above the rough Mid-Atlantic Ridge, and the diffusivity deduced for the bottom-most 150 meters exceeds 5 x 10(-4) meters squared per second. Such patterns in vertical mixing imply that abyssal circulations have complex spatial structures that are linked to the underlying bathymetry.     

The galilean satellites and jupiter: voyager 2 imaging science results

Voyager 2, during its encounter with the Jupiter system, provided images that both complement and supplement in important ways the Voyager 1 images. While many changes have been observed in Jupiter's visual appearance, few, yet significant, changes have been detected in the principal atmospheric currents. Jupiter's ring system is strongly forward scattering at visual wavelengths and consists of a narrow annulus of highest particle density, within which is a broader region in which the density is lower. On Io, changes are observed in eruptive activity, plume structure, and surface albedo patterns. Europa's surface retains little or no record of intense meteorite bombardment, but does reveal a complex and, as yet, little-understood system of overlapping bright and dark linear features. Ganymede is found to have at least one unit of heavily cratered terrain on a surface that otherwise suggests widespread tectonism. Except for two large ringed basins, Callisto's entire surface is heavily cratered.     

Behavior of Mustela putorius furo (the domestic ferret).

Behavior patterns exhibited by the domestic ferret, although similar to its wild cousins, are distinctly domestic in nature. Domestic ferrets use many different types of behaviors, including body posturing, animations, vocalizations, and scent markings. These behaviors may differ somewhat from ferret to ferret. The domestic ferret is best understood by observation and recognition of its behavior patterns and interactions as it plays and communicates with both humans and animals within its home environment. As with all other species of animals kept as pets, the clinician will be greatly benefited by urging the pet owner to regularly note typical behavior patterns for their individual pet. Following is a brief summary of behavioral changes noted in domestic ferrets that may aid the owner or keeper in the detection of potential illness or injury: A normally active ferret suddenly becoming quiet or vice-versa Any sudden increase or decrease in daily food and water intake Routine behaviors performed out of context or order, especially in older animals Any sudden increase or decrease in the speed at which routine behaviors are performed (such as urination, defecation, grooming, food, or water intake) Any sudden increase in the effort required to perform normal or routine behaviors Any sudden changes in personality or attitude toward other ferrets or toward other animals or people. The previous information was gathered over the last 15 years from personal observations, experiences, and studies of ferrets in the shelter, home, and animal hospital environments. This information regarding ferret behavior can assist the veterinarian in differentiating between normal and abnormal behaviors in domestic ferrets. This increased understanding of ferret behavior can aid in the diagnosis of injury and disease and assist the veterinarian in educating clients regarding ferret behavior, care, and recognition of potential disease.     

Comparative properties of N-acetyl derivatives of oxime N-methylcarbamates and aryl N-methylcarbamates as insecticides and acetylcholinesterase inhibitors

N-acylation of aryl N-methylcarbamates is known to reduce their mammalian toxicity considerably without adversely affecting their insecticidal activity. It has now been found that N-acylation of several insecticidal oxime carbamates results in loss of toxicity both to insects and mammals. Kinetic data for base-catalysed solvolysis and inhibition of acetylcholinesterase, together with published work on metabolism, are combined to provide a rationale for this unexpected observation and to account for the selective toxicity of aryl N-acetyl-N-methylcarbamates.