1,336 research outputs found
Surface water sanitation and biomass production in a large constructed wetland in the Netherlands
In Western-Europe, agricultural practices have contributed to environmental problems such as eutrophication of surface and ground water, flooding, drought and desiccation of surrounding natural habitats. Solutions that reduce the impact of these problems are urgently needed. Common reed (Phragmites australis) is capable of sanitizing surface water and may function as green energy source because of its high productivity. Here, the results of an experiment in a constructed wetland in the Netherlands are presented where two different sanitation treatments were compared. Depending on the residence time and volume per unit area, reed is capable to reduce the total amount of nitrogen in the water with average efficiencies from 32 to 47% and the total amount of phosphorous with 27â45%. Although biomass production still varies largely between different parts of the constructed wetland, a rapid increase in biomass was observed since planting. Constructed wetlands with reed provide opportunities to improve water quality and reed produces enough biomass to serve as green energy source. Moreover, these wetlands also function as a flood water reservoir and are possibly advantageous for biodiversity. The optimal moment of reed harvesting depends on the goal of the owner. This moment should be chosen wisely, as it may have consequences for reed filter regeneration, biomass production, biodiversity, methane emission and water sanitation efficiency
Scanning Imaging Absorption Spectrometer for Atmospheric Chartography carbon monoxide total columns: Statistical evaluation and comparison with chemistry transport model results
This paper presents a detailed statistical analysis of one year (September 2003 to August 2004) of global Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) carbon monoxide (CO) total column retrievals from the Iterative Maximum Likelihood Method (IMLM) algorithm, version 6.3. SCIAMACHY provides the first solar reflectance measurements of CO and is uniquely sensitive down to the boundary layer. SCIAMACHY measurements and chemistry transport model (CTM) results are compared and jointly evaluated. Significant improvements in agreement occur, especially close to biomass burning emission regions, when the new Global Fire Emissions Database version 2 (GFEDv2) is used with the CTM. Globally, the seasonal variation of the model is very similar to that of the SCIAMACHY measurements. For certain locations, significant differences were found, which are likely related to modeling errors due to CO emission uncertainties. Statistical analysis shows that differences between single SCIAMACHY CO total column measurements and corresponding model results are primarily explained by random instrument noise errors. This strongly suggests that the random instrument noise errors are a good diagnostic for the precision of the measurements. The analysis also indicates that noise in single SCIAMACHY CO measurements is generally greater than actual variations in total columns. It is thus required to average SCIAMACHY data over larger temporal and spatial scales to obtain valuable information. Analyses of monthly averaged SCIAMACHY measurements over 3° Ă 2° geographical regions indicates that they are of sufficient accuracy to reveal valuable information about spatial and temporal variations in CO columns and provide an important tool for model validation. A large spatial and temporal variation in instrument noise errors exists which shows a close correspondence with the spatial distribution of surface albedo and cloud cover. This large spatial variability is important for the use of monthly and annual mean SCIAMACHY CO total column measurements. The smallest instrument noise errors of monthly mean 3° Ă 2° SCIAMACHY CO total columns measurements are 0.01 Ă 1018 molecules/cm2 for high surface albedo areas over the Sahara. Errors in SCIAMACHY CO total column retrievals due to errors other than instrument noise, like cloud cover, calibration, retrieval uncertainties and averaging kernels are estimated to be about 0.05â0.1 Ă 1018 molecules/cm2 in total. The bias found between model and observations is around 0.05â0.1 1018 molecules/cm2 (or about 5%) which also includes model errors. This thus provides a best estimate of the currently achievable measurement accuracy for SCIAMACHY CO monthly mean averages
Adhesion force imaging in air and liquid by adhesion mode atomic force microscopy
A new imaging mode for the atomic force microscope(AFM), yielding images mapping the adhesion force between tip and sample, is introduced. The adhesion mode AFM takes a force curve at each pixel by ramping a piezoactuator, moving the siliconânitride tip up and down towards the sample. During the retrace the tip leaves the sample with an adhesion dip showing up in the force curve. Adhesion force images mapping parameters describing this adhesion dip, such as peak value, width, and area, are acquired onâline together with the sample topography. Imaging in air gives information on the differences in hydrophobicity of sample features. While imaging a mercaptopentadecaneâgold layer on glass in demineralized water, the adhesion force could be modulated by adding phosphate buffered saline
Association Between Clinical Pathways Leading to Medical Management and Prognosis in Patients With NSTEACS.
: A large proportion of patients with non-ST-segment elevation acute coronary syndrome (NSTEACS) are initially selected for medical management (MM) and do not undergo coronary revascularization during or immediately after the index event. The aim of this study was to explore the clinical pathways leading to MM in NSTEACS patients and their influence on prognosis. : Patient characteristics, pathways leading to MM, and 2-year outcomes were recorded in a prospective cohort of 5591 NSTEACS patients enrolled in 555 hospitals in 20 countries across Europe and Latin America. Cox models were used to assess the impact of hospital management on postdischarge mortality. : Medical management was the selected strategy in 2306 (41.2%) patients, of whom 669 (29%) had significant coronary artery disease (CAD), 451 (19.6%) had nonsignificant disease, and 1186 (51.4%) did not undergo coronary angiography. Medically managed patients were older and had higher risk features than revascularized patients. Two-year mortality was higher in medically managed patients than in revascularized patients (11.0% vs 4.4%; P < .001), with higher mortality rates in patients who did not undergo angiography (14.6%) and in those with significant CAD (9.3%). Risk-adjusted mortality was highest for patients who did not undergo angiography (HR = 1.81; 95%CI, 1.23-2.65), or were not revascularized in the presence of significant CAD (HR = 1.90; 95%CI, 1.23-2.95) compared with revascularized patients. : Medically managed NSTEACS patients represent a heterogeneous population with distinct risk profiles and outcomes. These differences should be considered when designing future studies in this population.<br/
HI Narrow Line Absorption in Dark Clouds
We have used the Arecibo telescope to carry out an survey of 31 dark clouds
in the Taurus/Perseus region for narrow absorption features in HI (
21cm) and OH (1667 and 1665 MHz) emission. We detected HI narrow
self--absorption (HINSA) in 77% of the clouds that we observed. HINSA and OH
emission, observed simultaneously are remarkably well correlated. Spectrally,
they have the same nonthermal line width and the same line centroid velocity.
Spatially, they both peak at the optically--selected central position of each
cloud, and both fall off toward the cloud edges. Sources with clear HINSA
feature have also been observed in transitions of CO, \13co, \c18o, and CI.
HINSA exhibits better correlation with molecular tracers than with CI.
The line width of the absorption feature, together with analyses of the
relevant radiative transfer provide upper limits to the kinetic temperature of
the gas producing the HINSA. Some sources must have a temperature close to or
lower than 10 K. The correlation of column densities and line widths of HINSA
with those characteristics of molecular tracers suggest that a significant
fraction of the atomic hydrogen is located in the cold, well--shielded portions
of molecular clouds, and is mixed with the molecular gas.
The average number density ratio [HI]/[\h2] is . The
inferred HI density appears consistent with but is slightly higher than the
value expected in steady state equilibrium between formation of HI via cosmic
ray destruction of H and destruction via formation of H on grain
surfaces. The distribution and abundance of atomic hydrogen in molecular clouds
is a critical test of dark cloud chemistry and structure, including the issues
of grain surface reaction rates, PDRs, circulation, and turbulent diffusion.Comment: 40 pages, 10 figures, accepted by Ap
Performance of the Two Aerogel Cherenkov Detectors of the JLab Hall A Hadron Spectrometer
We report on the design and commissioning of two silica aerogel Cherenkov
detectors with different refractive indices. In particular, extraordinary
performance in terms of the number of detected photoelectrons was achieved
through an appropriate choice of PMT type and reflector, along with some design
considerations. After four years of operation, the number of detected
photoelectrons was found to be noticeably reduced in both detectors as a result
of contamination, yellowing, of the aerogel material. Along with the details of
the set-up, we illustrate the characteristics of the detectors during different
time periods and the probable causes of the contamination. In particular we
show that the replacement of the contaminated aerogel and parts of the
reflecting material has almost restored the initial performance of the
detectors.Comment: 18 pages, 9 Figures, 4 Tables, 44 Reference
Integrated Filterbank for DESHIMA: A Submillimeter Imaging Spectrograph Based on Superconducting Resonators
An integrated filterbank (IFB) in combination with microwave kinetic
inductance detectors (MKIDs), both based on superconducting resonators, could
be used to make broadband submillimeter imaging spectrographs that are compact
and flexible. In order to investigate the possibility of adopting an IFB
configuration for DESHIMA (Delft SRON High-redshift Mapper), we study the basic
properties of a coplanar-waveguide-based IFB using electromagnetic simulation.
We show that a coupling efficiency greater than 1/2 can be achieved if
transmission losses are negligible. We arrive at a practical design for a 9
pixel x 920 color 3 dimensional imaging device that fits on a 4 inch wafer,
which instantaneously covers multiple submillimeter telluric windows with a
dispersion of f/df = 1000.Comment: 6 pages, 4 figures, submitted to LTD-14 / Journal of Low Temperature
Physic
HIFI spectroscopy of low-level water transitions in M82
We present observations of the rotational ortho-water ground transition, the
two lowest para-water transitions, and the ground transition of ionised
ortho-water in the archetypal starburst galaxy M82, performed with the HIFI
instrument on the Herschel Space Observatory. These observations are the first
detections of the para-H2O(111-000) (1113\,GHz) and ortho-H2O+(111-000)
(1115\,GHz) lines in an extragalactic source. All three water lines show
different spectral line profiles, underlining the need for high spectral
resolution in interpreting line formation processes. Using the line shape of
the para-H2O(111-000) and ortho-H2O+(111-000) absorption profile in conjunction
with high spatial resolution CO observations, we show that the (ionised) water
absorption arises from a ~2000 pc^2 region within the HIFI beam located about
~50 pc east of the dynamical centre of the galaxy. This region does not
coincide with any of the known line emission peaks that have been identified in
other molecular tracers, with the exception of HCO. Our data suggest that water
and ionised water within this region have high (up to 75%) area-covering
factors of the underlying continuum. This indicates that water is not
associated with small, dense cores within the ISM of M82 but arises from a more
widespread diffuse gas component.Comment: 5 pages, 4 figures. Accepted for publication in A&
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