371 research outputs found
Utilisation des resultats de la recherche et du developpement publics en Belgique = Utilization of the results of public research and development in Belgium. EUR 11529 FR. Innovation and Technology Collection.
The effect of cadmium and lead pollution on growth and physiological parameters of field beans (Vicia faba)
ArticleResearch on the impact of soil contamination on crops is important as plants directly
take up heavy metals from the soil through the roots, so heavy metals can enter the food chain.
The aim of this study was to investigate the impact of cadmium (Cd) and lead (Pb) pollution on
growth and physiological parameters of field beans. Plants in the vegetation experiment were
grown under controlled conditions. Changes in growth and physiological parameters were studied
at five levels of Cd (0–25 mg L
-1
) and at 6 levels of Pb in substrate: from (0–1,000 mg L
-1
) at the
first day of the experiment, to (0–2,000 mg L
-1
) at the end of the experiment after gradual Pb
additions after every sample collecting day. Methods used for analysing the plant material: the
content of amino acid proline and photosynthetic pigments were determined by
spectrophotometry; chlorophyll a fluorescence parameters – using continuous excitation
chlorophyll fluorimeter. The fresh weight of plant above-ground parts and roots was detected.
The growth and development of field beans was slightly influenced by increasing amount of Cd
and Pb in substrate only at the end of the experiment. The highest Cd treatments (Cd20 and Cd25)
caused 2.5 and 1.3 times increased proline concentration in bean leaves. The chlorophyll a + b
content and chlorophyll a fluorescence parameter Fv/Fm changed differently throughout the
experiment. In general, during the experiment, there was a tendency for the content of proline in
leaves for Pb treatments to be increased compared to control. At the end of the experiment the
content of proline in field bean leaves of the highest Pb treatments (Pb600 + 100 + 400 + 500,
Pb800 + 100 + 400 + 500 and Pb 1,000 + 100 + 400 + 500) was 1.66, 1.44 and 1.55 times higher,
respectively, than that of the control plant leaves. The negative impact of exposure to Pb on
chlorophyll a + b, chlorophyll a fluorescence parameter PIndex and Fv/Fm in bean leaves was less
pronounced compared to Cd. The obtained results confirm that field beans until their flowering
stage can grow and develop in the presence of a large amount of Cd and Pb in substrate without
significant growth inhibition and detrimental impact on physiological parameters, if optimal
cultivation conditions are provided
BOLD Noise Assumptions in fMRI
This paper discusses the assumption of Gaussian noise in the
blood-oxygenation-dependent (BOLD) contrast for functional MRI
(fMRI). In principle, magnitudes in MRI images follow a Rice
distribution. We start by reviewing differences between Rician and
Gaussian noise. An analytic expression is derived for the null
(resting-state) distribution of the difference between two Rician
distributed images. This distribution is shown to be symmetric,
and an exact expression for its standard deviation is derived.
This distribution can be well approximated by a Gaussian, with
very high precision for high SNR, and high precision for lower
SNR. Tests on simulated and real MR images show that subtracting
the time-series mean in fMRI yields asymmetrically distributed
temporal noise. Subtracting a resting-state time series from the
first results in symmetric and nearly Gaussian noise. This has
important consequences for fMRI analyses using standard
statistical tests
Effect of COVID vaccination on monthly migraine days:a longitudinal cohort study
BACKGROUND: This longitudinal cohort study aimed to investigate changes in migraine-related outcomes following COVID-19 infection and vaccination. METHODS: We identified 547 clinically diagnosed migraine patients from the Leiden Headache Center who kept a headache E-diary during the COVID-19 pandemic (February 2020 to August 2022). We sent a questionnaire to register their COVID-19 infection and/or vaccination dates. After applying inclusion criteria, n = 59 participants could be included in the infection analysis and n = 147 could be included in the vaccination analysis. Primary outcome was the change in monthly migraine days (MMD) between 1 month prior and 1 month post COVID-19 infection or vaccination. Secondary outcome variables were change in monthly headache days (MHD) and monthly acute medication days (MAMD). RESULTS:Vaccination against COVID-19 was associated with an increase in MMD (1.06; 95% confidence interval [CI] = 0.57-1.55; p < 0.001), MHD (1.52; 95% CI = 0.91-2.14; p < 0.001) and MAMD (0.72; 95% CI = 0.33-1.12; p < 0.001) in the first month post-vaccination. COVID-19 infection solely increased the number of MAMD (1.11; 95% CI = 0.10-1.62; p < 0.027), but no statistically significant differences in MMD or MHD were observed. CONCLUSIONS: Our findings imply that vaccination against COVID-19 is associated with an increase in migraine, indicating a possible role of inflammatory mediators in migraine pathophysiology.</p
Multichannel interference mitigation methods in radio astronomy
Radio-astronomical observations are increasingly corrupted by RF
interference, and online detection and filtering algorithms are becoming
essential. To facilitate the introduction of such techniques into radio
astronomy, we formulate the astronomical problem in an array signal processing
language, and give an introduction to some elementary algorithms from that
field. We consider two topics in detail: interference detection by rank
estimation of short-term covariance matrices, and spatial filtering by subspace
estimation and projection. We discuss experimental data collected at the
Westerbork radio telescope, and illustrate the effectiveness of the space-time
detection and blanking process on the recovery of a 3C48 absorption line in the
presence of GSM mobile telephony interference.Comment: 39 pages, 18 figures.Enhanced figures can be downloaded from
http://cas.et.tudelft.nl/~leshem/postscripts/leshem/figs34567.ps.gz To appear
in Astrophysical Journal Supplements serie
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