Oxygen isotopic compositions of asteroidal materials returned from Itokawa by the Hayabusa mission

Meteorite studies suggest that each solar system object has a unique oxygen isotopic composition. Chondrites, the most primitive of meteorites, have been believed to be derived from asteroids, but oxygen isotopic compositions of asteroids themselves have not been established. We measured, using secondary ion mass spectrometry, oxygen isotopic compositions of rock particles from asteroid 25143 Itokawa returned by the Hayabusa spacecraft. Compositions of the particles are depleted in (16)O relative to terrestrial materials and indicate that Itokawa, an S-type asteroid, is one of the sources of the LL or L group of equilibrated ordinary chondrites. This is a direct oxygen-isotope link between chondrites and their parent asteroid.     

Episodic acidification of freshwater systems in Canada — Physical and geochemical processes

The occurrence of episodic acidification in Canadian streams, lake waters and shallow groundwaters has been reviewed, and the contolling mechanisms identified. ‘Episodes’, which are periods of depressed alkalinity during hydrological events, have been studied mainly in southeastern Canada, and occur at all sites where there is sufficient time resolution of the observations, viz. Ontario, Quebec and Nova Scotia. An ‘alkaline episode’, where acidity decreases during an event, has been reported from one lake in the Canadian Artic. There is a bias towards the examination of episodes stimulated by snowmelt or rain-on-snow, since rainfall-stimulated episodes are poorly documented. Pre-event, rather than event, water dominates runoff during episodes. For this reason, biogeochemical reactions and the hydrological flowpaths in operation through the vadose and saturated zones are the principal controls on the chemical characteristics of episodes. Most episodes are dominated by base cation ‘dilution’ in circumneutral systems, and ‘increase in strong acid anions’ (particularly sulphate) in acidic systems. Episodes dominated by nitrification or organic acids or stimulated by sea salt input are rare or have not been decumented. Direct input of event water may dominate only during particular circumstances at snowmelt. Then, direct chemical inputs from lake ice and lake snow cover may be of importance in some systems.     

High impulsivity predicts the switch to compulsive cocaine-taking

Both impulsivity and novelty-seeking have been suggested to be behavioral markers of the propensity to take addictive drugs. However, their relevance for the vulnerability to compulsively seek and take drugs, which is a hallmark feature of addiction, is unknown. We report here that, whereas high reactivity to novelty predicts the propensity to initiate cocaine self-administration, high impulsivity predicts the development of addiction-like behavior in rats, including persistent or compulsive drug-taking in the face of aversive outcomes. This study shows experimental evidence that a shift from impulsivity to compulsivity occurs during the development of addictive behavior, which provides insights into the genesis and neural mechanisms of drug addiction.     

The "soil" of Mars (viking 1)

The location of the Viking 1 lander is most ideal for the study of soil properties because it has one footpad in soft material and one on hard material. As each soil sample was acquired, information on soil properties was obtained. Although analysis is still under way, early results on bulk density, particle size, angle of internal friction, cohesion, adhesion, and penetration resistance of the soil of Mars are presented.     

Enhanced neurofibrillary degeneration in transgenic mice expressing mutant tau and APP

JNPL3 transgenic mice expressing a mutant tau protein, which develop neurofibrillary tangles and progressive motor disturbance, were crossed with Tg2576 transgenic mice expressing mutant beta-amyloid precursor protein (APP), thus modulating the APP-Abeta (beta-amyloid peptide) environment. The resulting double mutant (tau/APP) progeny and the Tg2576 parental strain developed Abeta deposits at the same age; however, relative to JNPL3 mice, the double mutants exhibited neurofibrillary tangle pathology that was substantially enhanced in the limbic system and olfactory cortex. These results indicate that either APP or Abeta influences the formation of neurofibrillary tangles. The interaction between Abeta and tau pathologies in these mice supports the hypothesis that a similar interaction occurs in Alzheimer's disease.     

Alternative therapeutic options for medical management of epilepsy in apes

Phenobarbital has been the primary antiepileptic drug used in primates, but the dosage required for seizure control is frequently associated with significant side effects. Newer antiepileptic drugs and adjunctive therapies currently being used in human medicine provide additional options for treatment of nonhuman primates. This report describes different drug regimes used for control of epileptic seizures in apes at the Milwaukee County Zoo (Milwaukee, Wisconsin, U.S.A.), including the addition of acetazolamide to phenobarbital, levetiracetam, carbamazepine, and the use of extended cycle oral contraceptives to assist seizure control in female apes with catamenial epilepsy.     

Habitats of the British amphibians (4): Agricultural lowlands and a general discussion of requirements

Ponds on about 80 km² of farmland in Sussex were investigated with regard to breeding amphibians. The survey covered five different geological strata and included 60 ponds (out of a total of more than 200) marked on 1:25000 ordnance maps. Eighteen of these ponds were found on inspection not to exist; the remainder were characterised with respect to surface area, depth, pH, ionic score, aquatic vegetation, fish fauna and surrounding terrestrial habitats as well as for amphibian species. 14 pools contained amphibians; Triturus vulgaris was the most widespread (9 ponds) closely followed by T. helveticus (8 ponds). T. cristatus occurred at 5 sites, Rana temporaria at 2 and Bufo bufo not at all. The 2 frog sites were very shallow pools on pasture/woodland interfaces; the ideal newt pond had no fish, was 0·5–1·0 m deep and < 200 m² in surface area with 5–50% aquatic vegetation cover and a low ionic score (< 400 parts/10⁶). Callitriche-containing ponds were particularly favoured, and with terrestrial habitat there was a requirement for a scrub or woodland component.     

Sulfate in lakes of eastern Canada: Calculated yields compared with measured wet and dry deposition

Sulfate yields in eastern Canada, calculated as lake concentration times runoff, are presented on an approximately west to east axis, and are compared with wet deposition data from CANSAP (Canadian Network for Sampling Precipitation) and APN (Air Pollution Network) data on dry deposition. The agreement is very good, and shows clearly that dry deposition is greatest near the center of the continental pollution plume and is less important in remote areas. The good agreement also indicates that most of the sulfate in these lakes is from atmospheric deposition and that there is little retention of sulfate in their watersheds.