A comparison of six deconvolution techniques Madden, F N; Godfrey, K R; Chappell, M J ...
Journal of pharmacokinetics and biopharmaceutics,
06/1996, Letnik:
24, Številka:
3
Journal Article
We present results for the comparison of six deconvolution techniques. The methods we consider are based on Fourier transforms, system identification, constrained optimization, the use of cubic ...spline basis functions, maximum entropy, and a genetic algorithm. We compare the performance of these techniques by applying them to simulated noisy data, in order to extract an input function when the unit impulse response is known. The simulated data are generated by convolving the known impulse response with each of five different input functions, and then adding noise of constant coefficient of variation. Each algorithm was tested on 500 data sets, and we define error measures in order to compare the performance of the different methods.
Provider: Czech digital library/Česká digitální knihovna - Institution: National Medical Library/Národní lékařská knihovna - Data provided by Europeana Collections- Jaromír Křemen, J. Bláha, P. ...Kopecký, L. Bošanská, E. Kotrlíková, T. Roubíček, K. Anderlová, Štěpán Svačina, M. Matias, J. Rulíšek, R. Hovorka, M. Haluzík- Lit.: 26- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
Among the nitrated and oxygenated polycyclic aromatic hydrocarbons (NPAHs and OPAHs) are some of the most hazardous substances to public health, mainly because of their carcinogenicity and oxidative ...potential. Despite these concerns, the concentrations and fate of NPAHs and OPAHs in the atmospheric environment are largely unknown. Ambient air concentrations of 18 NPAHs, 5 quinones, and 5 other OPAHs were determined at two urban and one regional background sites in central Europe. At one of the urban sites, the total (gas and particulate) concentrations of Σ10OPAHs were 10.0 ± 9.2 ng/m3 in winter and 3.5 ± 1.6 ng/m3 in summer. The gradient to the regional background site exceeded 1 order of magnitude. Σ18NPAH concentrations were typically 1 order of magnitude lower than OPAHs. Among OPAHs, 9-fluorenone and (9,10)-anthraquinone were the most abundant species, accompanied by benzanthrone in winter. (9,10)-Anthraquinone represented two-thirds of quinones. We found that a large fraction of the target substance particulate mass was carried by submicrometer particles. The derived inhalation bioaccessibility in the PM10 size fraction is found to be ≈5% of the total ambient concentration of OPAHs and up to ≈2% for NPAHs. For 9-fluorenone and (9,10)-anthraquinone, up to 86 and 18%, respectively, were found at the rural site. Our results indicate that water solubility could function as a limiting factor for bioaccessibility of inhaled particulate NPAHs and OPAHs, without considerable effect of surfactant lipids and proteins in the lung lining fluid.
Optically active linear polyimides and hyperbranched poly (amic acid–imide) were prepared by using procedures varying in particular in the maximum temperature employed in their synthesis. The two ...types of linear polyimides were based on 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 1,2‐diaminocylohexane enantiomers or 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 2,2′‐diamino‐1,1′‐binaphthalene enantiomers. The amine‐terminated hyperbranched poly (amic acid–imide) was prepared from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 4,4′,4″‐triaminotriphenylmethane, and its end groups were modified with the chiral selectors N‐acetyl‐D‐phenylalanine or N‐acetyl‐L‐phenylalanine. The final structure of the products was analyzed by IR spectroscopy, and their optical activity was evaluated and confirmed by polarimetry or circular dichroism.
(Modified) polyimides based on enantiomeric low‐molecular‐weight compunds were prepared. The optical activity was transferred from these building blocks into the final polymer structures. The reaction temperatures up to 230°C do not contribute to racemization markedly. These polyimides are potentially suited for the use as enantioselective membranes.
Linear polyimides based on both of the 2,2´-diamino-1,1´-binaphthalene enantiomers and their racemic mixture were synthesized and characterized. A two-step synthetic route, consisting of the ...preparation of the polyimide precursor followed by its thermal imidization at temperatures not exceeding 200°C, was employed. The products were analyzed by FTIR and 1H NMR spectroscopy. All of the tested materials were nearly fully imidized after 25 h. The final polyimides possess high glass transition temperatures, are thermo-oxidatively stable and are soluble in common organic solvents as 1-methyl-2-pyrrolidone, tetrahydrofuran and chloroform; additionally, those prepared from the enantiomers show optical activity. The values of specific optical rotations for the polymers were higher than those for the corresponding monomers. However, the directions of their optical rotations were identical. Due to their rather low molar masses, the final polyimides form brittle self-standing films. Thin layers of these products on porous polyimide substrates were made under forming composite membranes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Nitrated monoaromatic hydrocarbons (NMAHs) are ubiquitous in the environment and an important part of atmospheric humic-like substances (HULIS) and brown carbon. They are ecotoxic and with ...underresearched toxic potential for humans. NMAHs were determined in size-segregated ambient particulate matter collected at two urban sites in central Europe, Ostrava and Kladno, Czech Republic. The average sums of 12 NMAHs (Σ
12
NMAH) measured in winter PM
10
samples from Ostrava and Kladno were 102 and 93 ng m
−3
, respectively, and 8.8 ng m
−3
in summer PM
10
samples from Ostrava. The concentrations in winter corresponded to 6.3–7.3% and 2.6–3.1% of HULIS-C and water-soluble organic carbon (WSOC), respectively. Nitrocatechols represented 67–93%, 61–73% and 28–96% of NMAHs in PM
10
samples collected in winter and summer at Ostrava and in winter at Kladno, respectively. The mass size distribution of the targeted substance classes peaked in the submicrometre size fractions (PM
1
), often in the PM
0.5
size fraction especially in summer. The bioaccessible fraction of NMAHs was determined by leaching PM
3
samples in two simulated lung fluids, Gamble’s solution and artificial lysosomal fluid (ALF). More than half of NMAH mass is found bioaccessible, almost complete for nitrosalicylic acids. The bioaccessible fraction was generally higher when using ALF (mimics the chemical environment created by macrophage activity, pH 4.5) than Gamble’s solution (pH 7.4). Bioaccessibility may be negligible for lipophilic substances (i.e. log
K
OW
> 4.5).
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