Jet Deflection by a Quasi-Steady-State Side Wind in the Laboratory

We present experimental data on the steady state deflection of a highly supersonic jet by a side-wind in the laboratory. The use of a long interaction region enables internal shocks to fully cross the jet, leading to the development of significantly more structure in the jet than in previous work with a similar setup (Lebedev et al., 2004). The ability to control the length of the interaction region in the laboratory allows the switch between a regime representing a clumpy jet or wind and a regime similar to a slowly varying mass loss rate. The results indicate that multiple internal oblique shocks develop in the jet and the possible formation of a second working surface as the jet attempts to tunnel through the ambient medium.     

Radiative Shock Experiments At Luli

We present the set-up and the results of a supercritical radiative shock experiment performed with the LULI nanosecond laser facility. Using specific designed targets filled with xenon gaz at low pressure, the propagation of a strong shock with a radiative precursor is evidenced. The main measured quantities related to the shock (electronic density, propagation velocities, temperature, radial dimension) are presented and compared with various numerical simulations.     

Impact of India–Asia collision on SE Asia: The record in Borneo

Borneo occupies a central position in the Sundaland promontory of SE Asia. It has a complex Cenozoic geological history of sedimentation and deformation which began at about the same time that India is commonly suggested to have started to collide with Asia. Some tectonic reconstructions of east and SE Asia interpret a large SE Asian block with Borneo at its centre which has been rotated clockwise and displaced southwards along major strike–slip faults during the Cenozoic due to the indentation of Asia by India. However, the geological history of Borneo is not consistent with the island simply forming part of a large block extruded from Asia. The large clockwise rotations and displacements predicted by the indentor model for Borneo are incompatible with palaeomagnetic evidence and there is no evidence that the major strike–slip faults of the Asian mainland reach Borneo. Seismic tomography shows there is a deep high velocity anomaly in the lower mantle beneath SE Asia interpreted as subducted lithosphere but it can be explained just as well by alternative tectonic models as by the indentor model. Very great thicknesses of Cenozoic sediments are present in Borneo and circum-Borneo basins, and large amounts of sediment were transported to the Crocker turbidite fan of north Borneo from the Eocene to the Early Miocene, but all evidence indicates that these sediments were derived from local sources and not from distant sources in Asia elevated by India–Asia collision. The Cenozoic geological history of Borneo records subduction of the proto-South China Sea and Miocene collision after this ocean lithosphere was eliminated, and a variety of effects resulting from long-term subduction beneath SE Asia. There is little to indicate that India–Asia collision has influenced the Cenozoic geological record in Borneo.     

Formulation and Evaluation of IMS, an Interactive Three-Dimensional Tropospheric Chemical Transport Model 3. Comparison of Modelled C2–C5 Hydrocarbons with Surface Measurements

In part 3 of this series of papers on a new 3-D global troposphericchemical transport model, using an Integrated Modelling System (IMS), anevaluation of the model performance in simulating global distributions andseasonal variations for volatile organic compounds (VOCs) in the atmosphere,is presented. Comparisons of model OH concentrations with previous modelstudies show consistent modelled OH levels from the subtropics tomidlatitudes, while more discrepancies occur over the tropical lowlatitudes, with IMS predicting the highest levels of OH. The close agreementbetween modelled OH concentrations over midlatitudes, where high surfaceNO_xand VOC concentrations are also found, is indicative of the strongphotochemical coupling between NO_x, VOCs and O₃ overthese latitudes. IMSOH concentrations in the Northern Hemisphere (NH) midlatitudes during summerare generally lower than available measurements, implying that models ingeneral are underestimating OH levels at this location and time of year.Substantial differences between model OH concentrations over low latitudesclearly highlight areas of uncertainty between models. IMS OH concentrationsare the highest in general of the models compared, one possible reason isthat biogenic emissions of species such as isoprene and monoterpenes arehighest in IMS, leading to higher O₃ levels and hence higher OH.Generally, the IMS VOC concentrations show a similar seasonality to themeasurements at most locations. In general though, IMS tends to underestimatethe NH wintertime VOC maximum and overestimate the NH summertime VOCminimum. Such an overestimate in summer could be due to IMSunderestimating OH levels, or an overestimation of VOC emissions or possiblya problem with model transport, all of these possibilities are explored.Except for n-pentane, the model underprediction of a VOC maximum during theNH winter month strongly suggests a missing emission mechanism in the modelor an underestimate of an existing one. It is very likely that there is alack of time varying emission sources in the model to account for theseasonal change in emission behaviour such as increasing energy usage (e.g.,electricity and gas), road transportation, engine performance, and otheranthropogenic factors which show strong seasonal characteristics. Theanomalous overprediction of wintertime n-pentane compared with its closesummertime prediction with the measurements suggest that emissions in thiscase may be too high.     

Relating forestry interpreter preference to sensitometric parameters of black and white and normal color aerial films

The photointerpretation accuracy of forest inventory surveys are highly contingent on the sensitometric attributes of aerial films. The sensitometric characteristics of the products that interpreters prefer to work with was determined as a basis for future specifications of 70 mm large-scale photography. Seven black and white and two color films were compared, of which color-positive film was clearly preferred. Of greater significance were the comparison results between the black and white films. Panchromatic films with an average gradient of 0.9 to 1.2 and a density range of 1.0–1.2 were most preferred for forest photo interpretation. Within each black and white film, interpreters preferred the higher contrast images characterized by the higher average gradients. In general, interpreter preference decreased as the spectral sensitivity of the black and white films increased     

Small-Scale Retrospective Ground Water Monitoring Study for Simazine in Different Hydrogeological Settings

A ground water monitoring study was conducted for the triazine herbicide simazine at 11 sites in the United States. The study used carefully selected, small-scale sites (average size: about 33 acres) with documented product use and sensitive hydrogeological settings. The sites selected were Tulare County, California (two sites); Fresno County, California; Sussex County, Delaware; Hardee and Palm Beach counties, Florida; Winnebago County, Illinois; Jackson County, Indiana; Van Buren and Berrien counties, Michigan; and Jefferson County, West Virginia. These sites satisfied the following criteria: a history of simazine use, including the year prior to the start of the study; permeable soil and vadose zone; shallow depth to water; no restrictive soil layers above the water table; and gentle slopes not exceeding 2 percent. A variety of crop types, climates, and irrigation practices were included. Monitoring well clusters (shallow and deep) were installed at each site except in California and West Virginia, where only shallow wells were installed. Simazine was monitored at these sites at quarterly intervals for a two-year period during 1986–1988.
The results of the study showed that out of 153 samples analyzed, 45 samples showed simazine detections. A substantial majority of the detections (32 out of 45) occurred in Tulare, Fresno, and Jefferson counties. The detections in these areas were attributed to mechanisms other than leaching, such as drainage wells, karst areas, surface water recharge, or point source problems. An additional 11 detections in Van Buren County were apparently due to an unknown upgradient source. Only one detection (in Palm Beach County, Florida) near the screening level of 0.1 ppb was attributed to possible leaching. The results of this investigation support the hypothesis that simazine does not leach significantly under field use conditions.     

The behaviour of platinum group elements in the surficial environment at Ferguson Lake, N.W.T., Rottenstone Lake, Sask. and Sudbury, Ont., Canada

A multidisciplinary geochemical study of the distribution, dispersion, and glacial dispersal, of the pge and associated elements has been undertaken within soil, till, humus, vegetation and water at Ferguson Lake, Northwest Territories, Rottenstone Lake, Saskatchewan and Sudbury, Ontario.As the pge generally are present at low levels in surficial materials, development work on analytical techniques was an essential part of this study.At Ferguson Lake, the spatial distribution patterns of Au, Pt and Pd in till clearly indicate the exposed gossan zones, as expected, but also indicate a possible extension of the zone beneath a peat bog- and till-covered area. Down-ice dispersal of Au, Pt and Pd is limited to one to two hundred metres, in the <63 μm component of the till samples collected from frost boils. In vegetation the pge enrichment extends for several hundred metres down-ice and is best defined by Pd in birch twigs. Detectable, although extremely low, levels of Pt (2.8 ppt) and Pd (2.0 ppt) are present in waters in the vicinity of the gossanous zones at Ferguson Lake.At Rottenstone Lake, moderate to high concentrations of pge, Au, and base metals were found in ashed twigs of black spruce and the hmc of the tills for a distance of less than two hundred metres down-ice of the mineralization. Low Pd and Au concentrations were present in ashed spruce twigs about one kilometre down-ice of the mineralization, where only the hmc of the tills yielded anomalous concentrations of Pt and Au. There appears to be only limited dispersal of the pge and Au. These data indicate that only the hmc and the spruce twigs are of value in detecting Pt and Au in this area. Palladium presents a different picture, being detectable in only some of the soils, absent in the tills and hmc, yet appreciably enriched in the twig ash. The inference is that Pd is moving in solution and is being somewhat adsorbed in the soil but is much more significantly being taken up by the plant roots.At the Sudbury areas the pge, hosted in the Ni-Cu mineralization, are best reflected by elevated levels in the ashed humus of almost all elements examined. There is only minimal response in pge and Au to the mineralization from any of the fractions of the soil; whereas the <2 μm fraction of the B-horizon soil reflects the mineralization by elevated levels of As, Sb, Se, Cr, Co, Ni, Cu, Pb and Zn. Only hmc from the tills show elevated pge, Au and variable enhancement in As, Sb, Se and the base metals. The < 2 μm portion of the tills tends to be highest in As, Se, Cr and the base metals.This ongoing study shows that surficial materials and vegetation are effective in identifying areas of concealed pge mineralization. Various pathfinder elements, primarily Cu and Ni, but perhaps also As, Se, Sb and the other base metals, in the < 2 μm B-horizon soils and tills, may be informative in a preliminary evaluation of the pge potential of an area, prior to undertaking the more expensive precious-metal analyses. Humus and vegetation both appear extremely effective, and most cost efficient, and heavy-mineral concentrates (hmc) appear effective, for identifying areas with pge potential, whereas hmc from tills appear most effective for zeroing in on the site of the pge mineralization.