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231.
C. L. Schiller S. Locquiao Timothy J. Johnson G.W. Harris 《Journal of Atmospheric Chemistry》2001,40(3):275-293
Ambient gas phase nitrous acid (HONO) has been measured by Tunable Diode Laser Absorption Spectroscopy with sub-ppbv detection limits. An R-branch line in the 1263.4 cm–1 3 band was found tobe free of interference and suitable for ambient HONO measurements. Nitrous acid was measured during the night and early morning at an urban site in Toronto, Canada, during the summer of 1998. Average mixing ratios, integrated over 30 minutes, ranged from below the minimum detection limit of 300 pptv to 1.9 ppbv, with the highest concentrations observed during the early morning hours. During the night of 19 June 1998, the concentration of HONO increased by as much as 0.5 ppbv/hr. The usual decrease in HONO after sunrise was delayed by a few hours, possibly due to a combination of an increase in the production rate of HONO with rush hour, and attenuation of the early morning light by high NO2 within the aerosol fog/haze. 相似文献
232.
Tamara T. Helfer Michael W. Regan Michele D. Thornley Tony Wong Kartik Sheth Stuart N. Vogel Douglas C.-J. Bock LEO Blitz Andy Harris 《Astrophysics and Space Science》2001,276(2-4):1131-1139
BIMA SONG is a systematic imaging study of the 3 mm CO J = 1 → 0molecular emission within the centres and discs of 44 nearby spiral galaxies on size scales of a few hundred parsecs
(6-9"). The overall goal of the survey is to study the role of molecular gas in the evolution of spiral galaxies. To this
end, BIMA SONG addresses 1) the distribution and physical conditions of the molecular gas in galactic discs and its relation
to star formation, 2) the effects of a stellar bar on the kinematics of molecular gas, including the possible inflow of gas
along a bar, and 3) the distribution and role of molecular gas in the central few hundred parsecs of active and quiescent
galaxies. The source list includes all (except M33and M31) 44 galaxies of Hubble types Sa–Sd, with declinations δ >−20°, visual magnitudes B < 11.0, velocities v
hel <2000 km s-1, and inclinations i < 70°. Beyond the specific scientific questions we will address, this survey will provide a unique database for astronomers who
study galaxies at all wavelengths.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
233.
Bacterial mitigation of pollutants in acid drainage using decomposable plant material and sludge 总被引:2,自引:0,他引:2
Effects of a clay-lime spiked sewage sludge and fresh decomposable ryegrass on the mitigation of an acid drainage were studied
in the laboratory. Treatments (dry ameliorant weight/leachate ratio) were: (1) sludge (air-dried) at rates of 0, 8, 16 and
24%, (2) ryegrass at 0, 1, 1.5 and 2% (dry weight), (3) sludge (at the above-mentioned rates) and 1.5% ryegrass mixture. Measurements
of mitigation (according to the criteria of changes in pH, Fe, S, Al and heavy metals) made every 10th day for 100 days showed
ryegrass/sludge combination the most effective while sustaining mitigation longest, with or without the influence of sulphate-reducing
bacteria (SRB). Sulphate and Fe in the acid drainage decreased in the order: sludge+ryegrass>sludge>ryegrass by 180, 40, 19;
and 96, 83 and 54% respectively, compared with controls. An 11-fold decrease in soluble Al was caused by the highest rate
of the combined sludge-ryegrass treatment but Al was doubled by the sludge-only treatment, and only minimally affected (2%
reduction) by the ryegrass-only treatment. For the sludge plus ryegrass treatments at the highest rate of application, pH
levels increased significantly, from 2.3 to >7 units and within 20 days of SRB activation, the concentration of Co, Cu, Mn,
Ni and Zn decreased 3-, 15-, 90-, 3- and 50-fold respectively.
Received: 30 March 1999 · Accepted: 31 January 2000 相似文献
234.
Thomas Stachel Gerhard P. Brey Jeff W. Harris 《Contributions to Mineralogy and Petrology》2000,140(1):1-15
Peridotitic inclusions in alluvial diamonds from the Kankan region of Guinea in West Africa are mainly of lherzolitic paragenesis.
Nevertheless, extreme Cr2O3 contents (max. 17 wt%) in some of the exclusively lherzolitic garnets document that the diamond source experienced a previous
stage of melt extraction in the spinel stability field. This initial depletion was followed by at least two metasomatic stages:
(1) enrichment of LREE and Sr and (2) introduction mainly of MREE–HREE and other HFSE (Ti, Y, Zr, Hf). The Ti- and HFSE-poor
character of stage (1) points towards a CHO-rich fluid or carbonatitic melt, the high HFSE in stage (2) favour silicate melts
as enriching agent. Eclogitic inclusions are derived from a large depth interval ranging from the lithosphere through the
asthenosphere into the transition zone. The occurrence of negative Eu anomalies in garnet and clinopyroxene from both lithosphere
and transition zone suggests a possible relationship to subducted oceanic crust. Lithospheric eclogitic inclusions are derived
from heterogeneous sources, that may broadly be divided into a low-Ca group with LREE depleted trace element patterns and
a high-Ca group representing a source with negative LREE–HREE slope that is moderately enriched in incompatible elements relative
to primitive mantle. High-Ca inclusions of majoritic paragenesis are significantly more enriched in incompatible elements,
such as in Sr and LREE. Calculated whole rock compositions require metasomatic enrichment even if a derivation from MORB is
assumed.
Received: 26 January 2000 / Accepted: 18 May 2000 相似文献
235.
236.
J. Aiken N. Rees S. Hooker P. Holligan A. Bale D. Robins G. Moore R. Harris D. Pilgrim 《Progress in Oceanography》2000,45(3-4)
The Atlantic Meridional Transect programme uses the twice-annual passage of the RRS James Clark Ross between the UK and the Falkland Islands, before and after the Antarctic research programme in the Austral Summer (see Aiken, J., & Bale, A. J. (2000). An introduction to the Atlantic Meridional Transect (AMT) Programme. Progress in Oceanography, this issue). This paper examines the scientific rationale for a spatially-extensive time and space series programme and reviews the relevant physical and biological oceanography of the Atlantic Ocean. The main scientific observations from the research programme are reported. These are set in the context of historical and contemporary observations pertinent to the principal objectives of the cruise, notably the satellite remotely sensed observations of ocean properties. The extent to which the programme goals have been realised by the research to date is assessed and discussed. New bio-optical signatures, which can be related to productivity parameters, have been derived. These can be used to interpret remotely sensed observations of ocean colour in terms of productivity and production processes such as the air/sea exchange of biogenic gases, which relate to the issues of climate change and the sustainability of marine ecosystems. 相似文献
237.
238.
Binbin Lu Martin Charlton Paul Harris A. Stewart Fotheringham 《International journal of geographical information science》2014,28(4):660-681
Geographically weighted regression (GWR) is an important local technique for exploring spatial heterogeneity in data relationships. In fitting with Tobler’s first law of geography, each local regression of GWR is estimated with data whose influence decays with distance, distances that are commonly defined as straight line or Euclidean. However, the complexity of our real world ensures that the scope of possible distance metrics is far larger than the traditional Euclidean choice. Thus in this article, the GWR model is investigated by applying it with alternative, non-Euclidean distance (non-ED) metrics. Here we use as a case study, a London house price data set coupled with hedonic independent variables, where GWR models are calibrated with Euclidean distance (ED), road network distance and travel time metrics. The results indicate that GWR calibrated with a non-Euclidean metric can not only improve model fit, but also provide additional and useful insights into the nature of varying relationships within the house price data set. 相似文献
239.
Climate model errors, feedbacks and forcings: a comparison of perturbed physics and multi-model ensembles 总被引:4,自引:4,他引:0
Matthew Collins Ben B. B. Booth B. Bhaskaran Glen R. Harris James M. Murphy David M. H. Sexton Mark J. Webb 《Climate Dynamics》2011,36(9-10):1737-1766
Ensembles of climate model simulations are required for input into probabilistic assessments of the risk of future climate change in which uncertainties are quantified. Here we document and compare aspects of climate model ensembles from the multi-model archive and from perturbed physics ensembles generated using the third version of the Hadley Centre climate model (HadCM3). Model-error characteristics derived from time-averaged two-dimensional fields of observed climate variables indicate that the perturbed physics approach is capable of sampling a relatively wide range of different mean climate states, consistent with simple estimates of observational uncertainty and comparable to the range of mean states sampled by the multi-model ensemble. The perturbed physics approach is also capable of sampling a relatively wide range of climate forcings and climate feedbacks under enhanced levels of greenhouse gases, again comparable with the multi-model ensemble. By examining correlations between global time-averaged measures of model error and global measures of climate change feedback strengths, we conclude that there are no simple emergent relationships between climate model errors and the magnitude of future global temperature change. Algorithms for quantifying uncertainty require the use of complex multivariate metrics for constraining projections. 相似文献
240.
Samer K. Abi Kaed Bey Douglas P. Connelly François-Eric Legiret Andy J. K. Harris Matthew C. Mowlem 《Ocean Dynamics》2011,61(10):1555-1565
In this work, we describe a high-resolution fluorometric shipboard analyser and an improved method to determine NH4+ in oligotrophic seawater. The limit of detection is <5 nM, calculated with 95% confidence level using the weighted regression
line applied to the standard addition method using real samples prepared with low nutrient seawater from the Atlantic. The
results are summarised and cross-compared with spiked artificial seawater (ASW) and spiked Milli-Q water samples. The analyser
has a precision of ±1–4% with a high performance over a wide range from 5 nM to 25 μM. The methodology of NH4+ analysis is based on the fluorescent product formed between o-pthaldialdehyde and NH4+ in the presence of sulfite. Due to the high resolution of the developed system, we were able to study in depth the sensitivity
of the method to salinity, amines, amino acids and potential interferences from particles/algae. The method was found to be
sensitive to salinity variations, reducing the signal by up to 85% at 5 nM; this effect decreased at higher concentrations
of ammonium. It was noted that the interference from amines at low concentrations was negligible; however, at either high
amino acid or high amine concentrations, the signal was depressed. To test for the effect of particles on the system, the
system was tested with samples containing phytoplankton (Dunaliella primolecta) cells at different concentrations prepared with ASW to simulate the effect of a phytoplankton bloom. This experiment assessed
the potential impact of both particles and other potential fluorescence interferences from cells and/or ammonium leaching
from cells. This experiment showed that a phytoplankton bloom could potentially have an impact of up to 12% on the signal
of interest. Thus, we propose that this method is suitable for oligotrophic environments rather than coastal and eutrophic
environments. The reagent was found to be stable for 17 days and standards of 1 μM were stable for 6 days under laboratory
conditions. The developed analyser was successfully demonstrated in the North Atlantic Ocean, in an area of oligotrophic,
low NH4+ oceanic waters. 相似文献