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1.
Dr M. J. Wooller D. L. Swain K. J. Ficken A. D. Q. Agnew F. A. Street-Perrott G. Eglinton 《第四纪科学杂志》2003,18(1):3-15
Woody, subalpine shrubs and grasses currently surround Lake Rutundu, Mount Kenya. Multiple proxies, including carbon isotopes, pollen and grass cuticles, from a 755‐cm‐long core were used to reconstruct the vegetation over the past 38 300 calendar years. Stable carbon‐isotope ratios of total organic carbon and terrestrial biomarkers from the lake sediments imply that the proportion of terrestrial plants using the C4 photosynthetic pathway was greater during the Late Pleistocene than in the Holocene. Pollen data show that grasses were a major constituent of the vegetation throughout the Late Pleistocene and Holocene. The proportion of grass pollen relative to the pollen from other plants was greatest at the last glacial maximum (LGM). Grass cuticles confirm evidence that C4 grass taxa were present at the LGM and that the majority followed the cold‐tolerant NADP‐MEC4 subpathway. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
Seasonal evolution of surface mixed layer in the Northern Arabian Sea (NAS) between 17° N–20.5° N and 59° E-69° E was observed
by using Argo float daily data for about 9 months, from April 2002 through December 2002. Results showed that during April
- May mixed layer shoaled due to light winds, clear sky and intense solar insolation. Sea surface temperature (SST) rose by
2.3 °C and ocean gained an average of 99.8 Wm−2. Mixed layer reached maximum depth of about 71 m during June - September owing to strong winds and cloudy skies. Ocean gained
abnormally low ∼18 Wm−2 and SST dropped by 3.4 °C. During the inter monsoon period, October, mixed layer shoaled and maintained a depth of 20 to
30 m. November - December was accompanied by moderate winds, dropping of SST by 1.5 °C and ocean lost an average of 52.5 Wm−2. Mixed layer deepened gradually reaching a maximum of 62 m in December. Analysis of surface fluxes and winds suggested that
winds and fluxes are the dominating factors causing deepening of mixed layer during summer and winter monsoon periods respectively.
Relatively high correlation between MLD, net heat flux and wind speed revealed that short term variability of MLD coincided
well with short term variability of surface forcing. 相似文献
3.
4.
Norbert Schwarzenbeck Ron Erley Belinda S. Mc Swain Peter A. Wilderer Robert L. Irvine 《洁净——土壤、空气、水》2004,32(1):16-24
Aerobic granular sludge was successfully cultivated in a sequencing batch reactor (SBR) treating wastewater from the malting process with a high content of particulate organic matter. At an organic loading rate of 3.2 kg/(m3 d) CODtotal and an influent particle concentration of 0.95 g/L MLSS an average removal of 50% in CODtotal and 80% in CODdissolved could be achieved. A comparison of granular and flocculent sludge grown under the same operating conditions showed no significant difference in removal efficiency although granules exhibited a higher metabolic activity in terms of specific oxygen uptake rate (rO2, X). Two distinct mechanisms of particle removal were observed for granular sludge: during initial granule formation, particles were incorporated into the biofilm matrix. For mature granules, a high level of protozoa growth on the granule surface accounted for the ability to remove particulate COD. Combined evaluation of the development in MLSS content and sludge bed settling rate (i.e., mean derivative of the normalized sludge volume) was found to be an adequate method for monitoring the characteristic settling properties of a granulizing sludge bed. By means of this method, a distinct substrate gradient out of several operating conditions was concluded to have the biggest impact on the formation of aerobic granular sludge. 相似文献
5.
Robert L. Brathwaite Hugh J. Cargill Anthony B. Christie Andrew Swain 《Mineralium Deposita》2001,36(1):1-12
Vein distributions in line samples from four epithermal Au–Ag deposits of the Hauraki Goldfield were logged and quantified
by vein spacing, vein density, vein thickness and percentage of vein extension. One deposit is hosted in andesite lavas (Martha
Hill), one in andesite lavas and dacite porphyry, dacitic tuffs and pyroclastic breccias (Golden Cross), and two in rhyolite
lavas and rhyolitic tuffs with minor andesite lavas or andesite dikes (Ohui and Wharekirauponga). The vein systems in these
deposits form fault-controlled arrays of extensional veins. Vein spacing distributions are non-fractal over two to three orders
of magnitude (1 mm to 5 m), and therefore fractal dimension statistics are not applicable. The coefficient of variation (Cv) of vein spacing was used as a measure of the degree of vein clustering. Rock type has a marked influence on vein spacing
distributions, with veining in rhyolite lava having lower average thickness and percentage extension, but a generally higher
degree of vein clustering compared with veining in andesite lava in the same deposit. Vein spacing distributions in well-jointed
lithologies, mainly andesite lava, have Cv values (0.8–1.2) that are indicative of anticlustered to weakly clustered patterns, particularly in the vein stockwork of
the upper part of the Golden Cross deposit. These Cv values are consistent with field observations that joints are a major control on vein spacing. In the poorly jointed dacitic
and rhyolitic rocks, the veins are weakly to strongly clustered as shown by higher Cv values (1.2–2.4), and are commonly associated with normal faults. Overall, andesite lava and dacite porphyry and pyroclastics
host thicker and more persistent veins than rhyolite lava and tuff. These larger veins contain significant volumes of high-grade
gold mineralisation. The higher chemical reactivity to hydrothermal fluids of andesite and dacite compared with rhyolite may
have aided propagation and thickening of the veins in andesite-hosted deposits. Within an individual epithermal deposit, location
close to thick veins, representing major fluid conduits, commonly overrides the effect of different lithologies. Sites that
are deeper and located within or adjacent to major vein structures have higher average vein thickness, percentage extension
and degree of vein clustering. Systematic collection and analysis of vein spacing, thickness and density data can be used
to define trends that are useful in the exploration of gold-bearing epithermal vein deposits.
Received: 25 August 1998 / Accepted: 23 December 1999 相似文献
6.
Wolf Tietze Gerhard Kortum W. R. Mead T. K. Poiker C. Paddick George Kish A. Njøs H. Mensching V. Haarmann Uzo M. Igbozurike M. M. Yoshino Mushtaqur Rahman Lage Wahlström J. Connell Kazimierz Dziewonski Wayland R. Swain J. Humlum G. W. Lüttig Haruko Kishimoto Mai Britt E. Mørk 《GeoJournal》1982,6(3):270-280
7.
Anthropogenic aerosols in the lower troposphere increase the absorption and scattering of solar radiation by air and clouds,
causing a warmer atmosphere and a cooler surface. It is suspected that these effects contribute to slow down the hydrological
cycle. We conducted a series of numerical experiments using a limited area atmospheric model to understand the impacts of
aerosol radiative forcing on the rainfall process. Experiments with different radiative conditions under an idealized setting
revealed that increasing atmospheric forcing and decreasing surface forcing of radiation causes reductions in rainfall. There
was no relationship of top of the atmosphere forcing to the rainfall yield. The model was then used to simulate a domain covering
southern part of Sri Lanka, over for the period from November 2002 to July 2003. For a given radiative forcing, instances
with lower rainfall yields showed larger fractional reductions in rainfall. The trends in seasonal rainfall observed over
the site in past 30 years in a different study confirms this finding. We conclude that the negative impact of increase of
anthropogenic aerosols on rainfall would be more severe on regions and seasons with lower rainfall yields. The consequences
of this problem on the industries that critically depend on well-distributed rainfall like non-irrigated agriculture and on
the general livelihood of societies in low-rain areas can be serious. 相似文献
8.
Albert M. Swain 《Quaternary Research》1978,10(1):55-68
A 2000-year accumulation of varved sediments from Hell's Kitchen Lake in north-central Wisconsin was analyzed for pollen, charcoal, and seeds. The varves provided an accurate time scale for the study. The pollen record indicates changes on two different time scales. Short-term changes lasting several decades appear to be superimposed on long-term changes lasting several centuries. The short-term changes are related to individual fires, and the long-term changes result from increases or decreases in the frequency of these perturbations. From 2000 to 1150 years ago the average interval between fires was about 100 years, and from 1150 to 120 years ago the interval increased to about 140 years. Evidence from pollen, seeds, and charcoal at Hell's Kitchen Lake suggests that at least two “moist” intervals occurred during the past 2000 years, one between 2000 and 1700 years ago and the other between 600 and 100 years ago. A third but minor “moist” period occurred about 1150 to 850 years ago. A pollen and seed diagram shows that these intervals are characterized by increased percentages of white pine pollen, hemlock pollen, and yellow birch seeds, and by decreased levels of charcoal. The “dry” interval of 1700 to 1150 years ago is characterized by increased percentages of paper birch seeds, oak pollen, and aspen pollen, along with high levels of charcoal. The times of climatic change indicated at Hell's Kitchen Lake are nearly synchronous with those based on studies of tree rings, soils, glacial activity, and other pollen studies from various regions of North America, but the direction of these inferred changes is not always the same. This result suggests that the long-wave pattern of the general circulation has been variable during the past 2000 years. 相似文献
9.
10.
This study investigates the potential for incorporating the elastic mechanisms found in fish propulsive systems into mechanical systems for the development of underwater propulsion. Physical and kinematic information associated with the steady swimming of the bonito and other scombrid species was used for the design. Several electroactive materials were examined for simulating muscle behavior and their relative suitability was compared. A dynamic analysis method adapted for muscle, which is a work-loop technique, would provide valuable information. However, the lack of such information on engineering materials made any direct comparison between the biological and mechanical systems difficult. Based on available information, nickel-titanium shape memory alloy (SMA) was better suited to produce relatively slow and powerful steady swimming of scombrid species. The simplified geometry of muscular systems and axial tendons was adapted. These arrangements alleviate the limited strain of the SMA by trading force for distance and provide an effective force transmission pathways to the backbone. 相似文献