Experimental stream acidification — the influence of sediment and streambed vegetation

An acidification experiment was conducted on a small stream in the Loch Ard area of central Scotland. The stream was chosen because of its large, flow related, variation in pH (5.9-4.0). Two acid additions were made to approximately pH 3.5–3.7. The results indicated a strong correlation between labile aluminium and hydrogen, and a noticeable hysteresis in the response of calcium and hydrogen. It is hypothesised that divalent cation response is a result of ion-exchange mechanisms involving the streambed vegetation, with aluminium release resulting primarily from exchange reactions with streambed sediment stores. Data from a program of stream spot sampling have been analysed in an attempt to elucidate the contribution of different sources of aluminium under different flow conditions. Streambed sources of aluminium contribute significantly under low flow conditions; however, at high flow, additional sources of aluminium must contribute to match observed streamwater chemistry.     

Glacio-periglacial landforms within the Susquehanna Great Bend area of New York and Pennsylvania

Previous attention has been called to the morphology of the glaciated Appalachian Plateau, including periglacial phenomena (Coates, 1970; Conners, 1969). This paper deals with an unusually well-developed hierarchy of small landforms in the Great Bend area of the Susquehanna River. Essential properties of these features include: (1) concentration in N-S valleys, (2) till composition, (3) concavo-convex form, sometimes ending in a hill on the valley floor, (4) alternation with steep, truncated bedrock spurs, (5) a col in the interfluve at their head. These characteristics could be explained by the following sequence of events. A prior fluvial landscape was eroded with tributary streams forming lateral valleys that head in cols along the divides. The main stream flowed south between interlocking spurs. Ice then widened the valley, leaving truncated spurs and a straightened stream. Deposition of locally derived till filled tributary valleys, similar to till shadows (Coates, 1966). In periglacial conditions, while nivation was widening the tributary valley heads, solifluction in the unstable till was forming the concavo-convexities that alternate with the truncated bedrock spurs. The hierarchy of forms range from minor convexities to small hills on the main valley floor. Thus, the features are primarily of periglacial origin, but owe their development and position to prior subaerial and glacial events. The cycle may have occurred during more than a single glacial episode. The recession of bedrock spurs and the valley floor convexity of the till features have caused a reversal in stream sinuosity of the main valley.     

Lunar baselines and libration from differential Vlbi observations of alseps

Differential very-long-baseline interferometric observations of signals from Apollo Lunar Surface Experiment Package telemetry transmitters will yield the relative projected positions of the transmitters with uncertainty of only 1-3 m, set mainly by uncertainty of the lunar ephemeris. Noise and systematic instrumental errors which in the past affected similar observations have been reduced to the equivalent of a few centimeters on the lunar surface by the development of a new type of differential receiver. Continued observations should yield a determination of the motion of the Moon about its center of mass with uncertainty less than 1 s of selenocentric arc. Improvements (by other means) in our knowledge of the Moon's orbital motion would allow a further order-of-magnitude refinement in the libration and relative position results obtainable by differential VLBI.Communication presented at the conference on Lunar Dynamics and Observational Coordinate Systems held January 15–17, 1973 at the Lunar Science Institute, Houston, Tex. U.S.A.     

SIX METEORITES FROM KANSAS: PETROGRAPHIC OBSERVATIONS AND RARE GASES

Electron microprobe analyses and petrographic observations demonstrate that Almelo Township (L6), Beeler (LL6), Kalvesta (H4), Phillips County (L6), and Yocemento (L5) are typical ordinary chondrites. Selden has abnormally iron-rich silicates and nickel-rich metal, and it may have been a lower petrologic type that has been shocked to an LL5. Shielding corrected exposure ages range from 0.80 m.y. (Kalvesta) to 47.0 m.y. (Yocemento).     

Conservation and community in the new South Africa: A case study of the Mahushe Shongwe Game Reserve

The idealization of natural landscapes and peoples during colonialism, coupled with the popularity of sustainable development in the postcolonial era, has contributed to the expansion of conservation planning throughout the African continent. Concerns surrounding the promotion of national and international conservation agendas at the expense of local livelihood needs have generated interest in community conservation projects that attempt to include local participation and knowledge in natural resource management. The early excitement associated with community conservation has waned in light of recent assessments that it has been unsuccessful in meeting its ecological and social goals. This parallels other research that suggests communities are understood in generic or homogenous ways that influence how these initiatives are understood. Using a case study of the Mahushe Shongwe Game Reserve, this paper evaluates how rural households access environmental and economic resources to produce livelihoods, and how these access patterns impact their views of the project. It is argued that there are significant livelihood variations within the community that shape the ways households engage with, and benefit from, conservation planning. Rather than strictly viewing Mahushe Shongwe as a constraint to environmental resource access or site for limited employment, community members identify a number of benefits from its existence including education and development opportunities. Additionally, transformations in governance systems in the region impact community views of the project since younger residents are less likely to engage with the Matsamo Tribal Authority, which participates in managing the reserve. The consequence is that conservation has various impacts and meanings within a specific community that remain tied to the livelihood and governance systems being renegotiated in the post-apartheid era.     

PSR J1012+5307: younger than it looks?

Lorimer et al. have recently reported that the spin-down age (∼7 × 10⁹ yr) of the low-mass binary pulsar PSR J1012+5307 is much higher than the cooling age (3 × 10⁸ yr) of its white dwarf companion. The proposed solutions for this discrepancy are outlined and discussed. In particular, the revised cooling age estimate proposed by Alberts et al. agrees with data from other low-mass binary pulsar systems if a transition to the 'classical' cooling regime occurs between ∼0.14 and ∼0.28 M_⊙. If this transition is excluded, PSR J1012+5307 seems to have finished its accretion phase far from the spin-up line.     

Diverse paths: the elderly British in Tuscany

"This paper investigates the life, migration and retirement experiences of elderly British residents of Tuscany and its adjacent districts.... Many pathways have led the elderly British to Tuscany; only a minority have simply migrated from the UK on retirement.... Key themes explored include class background, reasons for migration to Tuscany, previous connections to Italy, post-retirement behaviour, integration and future plans. The findings challenge some commonly-held ?expectations' about the nature of retirement migration."