Publications by authors named "Pavel Svehla"

10 Publications

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Thermal thickening of nitrified liquid phase of digestate for production of concentrated complex fertiliser and high-quality technological water.

J Environ Manage 2020 Dec 27;276:111250. Epub 2020 Aug 27.

Department of Agro-Environmental Chemistry and Plant Nutrition, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Kamycka 129, Prague, 165 21, Czech Republic. Electronic address:

Large production of liquid phase of digestate (LPD) characterised by low dry matter content increases the costs of LPD storage and transportation. Additionally, significant nitrogen losses result from LPD handling. The operation of biogas plants also requires large amounts of technological water, a scarce resource. The method of LPD nitrification and subsequent thermal thickening as a promising alternative treatment able to overcome those problems was investigated. The properties of thermally thickened nitrified LPD and of the distillate derived from vacuum evaporation of nitrified LPD were examined. The results show that over 99.9% of nitrogen was accumulated in thickened nitrified LPD. Total nitrogen (TN) concentration in thickened LPD ranged from 12 to 18 g/L depending on the distillate/thickened LPD volume ratio applied. The thickened LPD was also richer in other nutrients, which indicates its possible use as a concentrated complex fertiliser. TN concentration and conductivity in the distillate did not exceed 6 mg/L and 0.03 mS/m respectively, suggesting that the distillate may be useful as alternative source of technological water. It was concluded that the system consisting of nitrification and subsequent thermal thickening of nitrified LPD yields final products exhibiting significantly superior properties compared to thermal thickening of raw LPD, without requiring any additional chemical agents. The quality of these products is comparable to those obtained through advanced membrane processes.
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http://dx.doi.org/10.1016/j.jenvman.2020.111250DOI Listing
December 2020

Intracellular manganese enhanced MRI signals reflect the frequency of action potentials in Aplysia neurons.

J Neurosci Methods 2018 02 14;295:121-128. Epub 2017 Dec 14.

NeuroSpin, CEA Saclay, 91191 Gif-sur-Yvette, France. Electronic address:

Background: Manganese-enhanced magnetic resonance imaging (MEMRI) is an increasingly popular alternative to standard functional MRI methods in animal studies. The contrast in MEMRI images is based on the accumulation of Mn ions inside neurons, and, since manganese can serve as calcium analogue, this accumulation reflects calcium dynamics providing versatile information about brain neuroarchitecture and functionality. However, despite its use as a functional imaging tool, the exact relationship between the MEMRI signal and neuronal activity remains elusive.

New Method: In order to better understand the mechanisms underlying Mn accumulation resulting in MEMRI signal enhancement we investigated single neuron responses of isolated Aplysia buccal ganglia subjected to chemical (dopamine) or electrical stimulation of an input nerve (oesophageal nerve). The elicited electrical activity that represents a fictive feeding was recorded with electrophysiological methods and the Mn uptake in individual neurons was evaluated with MEMRI at 17.2T.

Results & Comparison With Existing Method(s): We show a positive correlation between bursts of electrical activity and MEMRI signal intensity in identified neurons and demonstrate that the MEMRI signal reflects mainly fast and high membrane depolarization processes such as action potentials, and it is not sensitive to slow and small membrane depolarizations, such as post-synaptic potentials.
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http://dx.doi.org/10.1016/j.jneumeth.2017.12.008DOI Listing
February 2018

Quantitative DLA-based compressed sensing for T-weighted acquisitions.

J Magn Reson 2017 08 9;281:26-30. Epub 2017 May 9.

NeuroSpin, CEA Saclay, 91191 Gif-sur-Yvette, France; University Paris-Saclay, XI, 91450 Orsay, France. Electronic address:

High resolution Manganese Enhanced Magnetic Resonance Imaging (MEMRI), which uses manganese as a T contrast agent, has great potential for functional imaging of live neuronal tissue at single neuron scale. However, reaching high resolutions often requires long acquisition times which can lead to reduced image quality due to sample deterioration and hardware instability. Compressed Sensing (CS) techniques offer the opportunity to significantly reduce the imaging time. The purpose of this work is to test the feasibility of CS acquisitions based on Diffusion Limited Aggregation (DLA) sampling patterns for high resolution quantitative T-weighted imaging. Fully encoded and DLA-CS T-weighted images of Aplysia californica neural tissue were acquired on a 17.2T MRI system. The MR signal corresponding to single, identified neurons was quantified for both versions of the T weighted images. For a 50% undersampling, DLA-CS can accurately quantify signal intensities in T-weighted acquisitions leading to only 1.37% differences when compared to the fully encoded data, with minimal impact on image spatial resolution. In addition, we compared the conventional polynomial undersampling scheme with the DLA and showed that, for the data at hand, the latter performs better. Depending on the image signal to noise ratio, higher undersampling ratios can be used to further reduce the acquisition time in MEMRI based functional studies of living tissues.
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http://dx.doi.org/10.1016/j.jmr.2017.05.002DOI Listing
August 2017

Nitrification in a completely stirred tank reactor treating the liquid phase of digestate: The way towards rational use of nitrogen.

Waste Manag 2017 Jun 3;64:96-106. Epub 2017 Apr 3.

Department of Agro-Environmental Chemistry and Plant Nutrition, Czech University of Life Sciences Prague, Kamycka 129, Prague 165 21, Czech Republic.

The nitrification of the liquid phase of digestate (LPD) was conducted using a 5L completely stirred tank reactor (CSTR) in two independent periods (P1 - without pH control; P2 - with pH control). The possibility of minimizing nitrogen losses during the application of LPD to the soil as well as during long-term storage or thermal thickening of LPD using nitrification was discussed. Moreover, the feasibility of applying the nitrification of LPD to the production of electron acceptors for biological desulfurization of biogas was assessed. Despite an extremely high average concentration of ammonia and COD in LPD reaching 2470 and 9080mg/L, respectively, nitrification was confirmed immediately after the start-up of the CSTR. N-NO concentration reached 250mg/L only two days after the start of P1. On the other hand, P1 demonstrated that working without pH control is a risk because of the free nitrous acid (FNA) inhibition towards nitrite oxidizing bacteria (NOB) resulting in massive nitrite accumulation. Up to 30.9mg/L of FNA was present in the reactor during P1, where the NOB started to be inhibited even at 0.15mg/L of FNA. During P2, the control of pH at 7.0 resulted in nitrogen oxidation efficiency reaching 98.3±1.5% and the presence of N-NO among oxidized nitrogen 99.6±0.4%. The representation of volatile free ammonia within total nitrogen was reduced more than 1000 times comparing with raw LPD under these conditions. Thus, optimum characteristics of the tested system from the point of view of minimizing the nitrogen losses as well as production of electron acceptors for the desulfurization of biogas were gained in this phase of reactor operation. Based on the results of the experiments, potential improvements and modifications of the tested system were suggested.
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http://dx.doi.org/10.1016/j.wasman.2017.03.041DOI Listing
June 2017

Anaerobic digestion of grass: the effect of temperature applied during the storage of substrate on the methane production.

Environ Technol 2017 Jul 17;38(13-14):1716-1724. Epub 2016 Oct 17.

a Department of Agro-Environmental Chemistry and Plant Nutrition, Faculty of Agrobiology, Food and Natural Resources , Czech University of Life Sciences Prague , Prague - Suchdol , Czech Republic.

Within this research, biogas production, representation of methane in biogas and volatile solids (VSs) removal efficiency were compared using batch tests performed with the samples of intensively and extensively planted grasses originating from public areas. Before the batch tests, the samples were stored at different temperatures achievable on biogas plants applying trigeneration strategy (-18°C, +3°C, +18°C and +35°C). Specific methane production from intensively planted grasses was relatively high (0.33-0.41 m/kg VS) compared to extensively planted grasses (0.20-0.33 m/kg VS). VSs removal efficiency reached 59.8-68.8% for intensively planted grasses and 34.6-56.5% for extensively planted grasses. Freezing the intensively planted grasses at -18°C proved to be an effective thermal pretreatment leading to high biogas production (0.61 m/kg total solid (TS)), high representation of methane (64.0%) in biogas and good VSs removal efficiency (68.8%). The results of this research suggest that public areas or sport parks seem to be available, cheap and at the same time very effective feedstock for biogas production.
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http://dx.doi.org/10.1080/09593330.2016.1241305DOI Listing
July 2017

Properties of vermicompost aqueous extracts prepared under different conditions.

Environ Technol 2017 Jun 23;38(11):1428-1434. Epub 2016 Sep 23.

a Department of Agro-Environmental Chemistry and Plant Nutrition , Czech University of Life Sciences Prague , Prague , Czech Republic.

The aim of this work was to determine the influence of aeration and time of extraction on the agrochemical properties of aqueous extracts from vermicomposts made from horse manure (M) and apple pomace (P) waste. There were two extract treatments: stirring without aeration (S), and stirring with aeration (A) for 48 h. Aeration significantly increased the levels of electrical conductivity (EC) and the concentration of [Formula: see text], [Formula: see text], and macro-elements in the extracts. In the (A) treatment, the extraction efficiency of K and Mg increased twofold, and the extraction efficiency of Ca and P increased by one-third compared with the (S) treatment. Simultaneously, the extracts prepared under aeration were characteristic with a higher pH value compared with non-aerated variants. The EC and content of macro-elements in the extracts increased proportionally with time. Their highest growth was found within the first 6 h. After 48 h, the highest release of macro-elements into the extract was found in the case of the horse manure under stirring with aeration.
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http://dx.doi.org/10.1080/09593330.2016.1231225DOI Listing
June 2017

A New Class of Potent N-Methyl-D-Aspartate Receptor Inhibitors: Sulfated Neuroactive Steroids with Lipophilic D-Ring Modifications.

J Med Chem 2015 Aug 29;58(15):5950-66. Epub 2015 Jul 29.

‡Institute of Physiology, Academy of Sciences of the Czech Republic v.v.i., Videnska 1083, Prague 4, 14220, Czech Republic.

N-Methyl-D-aspartate receptors (NMDARs) are glutamate-gated ion channels that play a crucial role in excitatory synaptic transmission. However, the overactivation of NMDARs can lead to excitotoxic cell damage/death, and as such, they play a role in numerous neuropathological conditions. The activity of NMDARs is known to be influenced by a wide variety of allosteric modulators, including neurosteroids, which in turn makes them promising therapeutic targets. In this study, we describe a new class of neurosteroid analogues which possess structural modifications in the steroid D-ring region. These analogues were tested on recombinant GluN1/GluN2B receptors to evaluate the structure-activity relationship. Our results demonstrate that there is a strong correlation between this new structural feature and the in vitro activity, as all tested compounds were evaluated as more potent inhibitors of NMDA-induced currents (IC50 values varying from 90 nM to 5.4 μM) than the known endogeneous neurosteroid-pregnanolone sulfate (IC50 = 24.6 μM).
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http://dx.doi.org/10.1021/acs.jmedchem.5b00570DOI Listing
August 2015

The impact of influent total ammonium nitrogen concentration on nitrite-oxidizing bacteria inhibition in moving bed biofilm reactor.

Water Sci Technol 2014 ;69(6):1227-33

Department of Water Technology and Environmental Engineering, Institute of Chemical Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic E-mail:

The application of nitrification-denitrification over nitrite (nitritation-denitritation) with municipal (i.e. diluted and cold (or low-temperature)) wastewater can substantially improve the energy balance of municipal wastewater treatment plants. For the accumulation of nitrite, it is crucial to inhibit nitrite-oxidizing bacteria (NOB) with simultaneous proliferation of ammonium-oxidizing bacteria (AOB). The present study describes the effect of the influent total ammonium nitrogen (TAN) concentration on AOB and NOB activity in two moving bed biofilm reactors operated as sequencing batch reactors (SBR) at 15 °C (SBR I) and 21 °C (SBR II). The reactors were fed with diluted reject water containing 600, 300, 150 and 75 mg TAN L(-1). The only factor limiting NOB activity in these reactors was the high concentrations of free ammonia and/or free nitrous acid (FNA) during the SBR cycles. Nitrite accumulation was observed with influents containing 600, 300 and 150 mg TAN L(-1) in SBR I and 600 and 300 in SBR II. Once nitrate production established in the reactors, the increase of influent TAN concentration up to the original 600 mg TAN L(-1) did not limit NOB activity. This was due to the massive development of NOB clusters throughout the biofilm that were able to cope with faster formation of FNA. The results of the fluorescence in situ hybridization analysis preliminarily showed the stratification of bacteria in the biofilm.
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http://dx.doi.org/10.2166/wst.2013.757DOI Listing
May 2014

Effect of composting on the mobility of arsenic, chromium and nickel contained in kitchen and garden waste.

Bioresour Technol 2012 Dec 25;126:444-52. Epub 2011 Nov 25.

Department of Agro-Environmental Chemistry and Plant Nutrition, Czech University of Life Sciences Prague, Kamycka 129, 165 21 Prague 6, Czech Republic.

The study was focused on evaluation of possible changes in As, Cr, and Ni mobility and fractionation during composting of kitchen and garden waste. Fresh bio-waste taken up seasonally was thoroughly mixed with woodchips in the wet weight portion of 3:1 and the mixture was put into batch-wise aerated fermenters under 3 air flow rates. An increased drop in exchangeable Cr and Ni was found in kitchen and garden waste after 12 weeks of composting, respectively. The exchangeable content of As decreased only during kitchen waste composting. The order of fractions in the final compost was as follows: residual>oxidizable>exchangeable>reducible. The proportion of Cr and Ni in exchangeable fraction decreased after composting more than 3- and 4-fold, respectively. Results proved that an intensive composting process is a suitable method for immobilization of Cr and Ni, and for decreasing total As contained in household bio-waste.
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http://dx.doi.org/10.1016/j.biortech.2011.11.053DOI Listing
December 2012

Composition and parameters of household bio-waste in four seasons.

Waste Manag 2011 Jul 17;31(7):1450-60. Epub 2011 Mar 17.

Department of Agro-Environmental Chemistry and Plant Nutrition, Czech University of Life Sciences, Kamycka 129, Prague 165 21, Czech Republic.

Bio-waste makes up almost half portion of municipal solid waste. The characterization of household bio-waste is important in determining the most appropriate treatment method. The differences in composition and parameters of bio-waste derived from urban settlement (U-bio-waste) and family houses (F-bio-waste) during the four climate seasons are described in this paper. Twelve components and 20 parameters for bio-waste were evaluated. The composition of U-bio-waste was almost steady over those seasons, unlike F-bio-waste. U-bio-waste was comprised mainly (58.2%) of fruit and vegetable debris. F-bio-waste was primarily made up of seasonal garden components. The amount of variation among seasons in both type of bio-waste increased in sequence: basic parameters
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http://dx.doi.org/10.1016/j.wasman.2011.02.016DOI Listing
July 2011