Publications by authors named "Szczepanik P"

The concept of entropy is not uniquely relevant to the statistical mechanics but, among others, it can play pivotal role in the analysis of a time series, particularly the stock market data. In this area, sudden events are especially interesting as they describe abrupt data changes with potentially long-lasting effects. Here, we investigate the impact of such events on the entropy of financial time series.

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We report a new synthetic strategy for the flexible preparation of forskolin-like molecules. The approach is different from the previously published works and employs a convergent assembly of the tricyclic labdane-type core from pre-functionalized cyclic building blocks. Stereoselective Michael addition enabled the fragment coupling with excellent control over three newly created contiguous stereocenters, all-carbon quaternary centers included.

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Knowledge about horses from early medieval (10th-13th c.) Poland has been largely based on historical and archaeological data. Archaeozoological information has only been used to a limited extent.

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A large-scale synthesis of known Ru olefin metathesis catalyst VII featuring an unsymmetrical N-heterocyclic carbene (NHC) ligand with one 2,5-diisopropylphenyl (DIPP) and one thiophenylmethylene N-substituent is reported. The optimised procedure does not require column chromatography in any step and allows for preparation of up to 0.5 kg batches of the catalyst from simple precursors.

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This work is the first report when multiharmonic analysis (MHA) was applied for electron paramagnetic resonance imaging (EPRI) for in vivo applications. Phantom studies were performed for established methodology, and in vivo imaging was conduct as a proof-of-concept. Phantom studies showed at least six times improvement of the signal - to - noise (S/N) ratio.

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A new method for fast 2D Electron Paramagnetic Resonance Imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradient, whose orientation is changed at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples.

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A new method for fast spectral-spatial electron paramagnetic resonance imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradients, whose amplitude is modulated at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples.

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The rich fossil fauna in the Middle Jurassic claystones that crop out in the Krakow-Czestochowa Upland is extensively replaced by sulfide minerals, mainly pyrite. Sphalerite (ZnS) is rare and restricted to the internal casts of gastropods, often together with framboidal and euhedral pyrite and calcite. Scanning electron microscopy-energy dispersive spectrometer study was undertaken to explain this curious association.

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The proposed cholic precursor, 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-[3H]cholestan-26-oic acid, and [14C]cholesterol were infused intravenously at a constant rate into two dogs for 25 days. If the specific activities of trihydroxy[3H]cholestanoic acid and [3H]cholic acid will be equal after an isotopic steady-state is achieved. The specific activities of [14C]deoxycholic acid (formed from [14C]cholic acid) isolated in the stool of these two dogs were equal the last four days of the infusion indicating that labeled deoxycholic acid (and presumably labeled cholic acid) was in an isotopic steady-state.

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Changes in bile saturation and biliary bile acid composition in patients with gallstones who received chenodeoxycholic ("chenic") acid, cholic acid, or placebo were measured. Chenodeoxycholic induced bile desaturation; this effect was attributable solely to a decrease in the proportion of cholesterol. By gas chromatography, chenodeoxycholic acid increased substantially in the biliary bile acids of patients receiving it, and by mass spectrometry, no unusual bile acids were detected in appreciable amounts.

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The stationary phase Poly S-179 has been found to offer distinct advantages over the previously reported SP-525 for the gas-liquid chromatographic separation of bile acid methyl ester acetates. Relative retention times of these bile acid derivatives are compared on the two phases.

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The effect of deoxycholate ingestion, 750 mg per day, on bile acid kinetics, biliary bile acid composition, and biliary lipid secretion was studied in 7 healthy volunteers. Bile acid kinetics were measured by isotope dilution, and hourly outputs of bile acid, cholesterol, and phospholipid were quantitated by a duodenal perfusion technique during a 24-hr period which included three liquid meals and an overnight fast. Biliary bile acid composition was assessed by coupled gas chromatography-mass spectrometry.

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The gas-liquid chromatographic retention times on 0.5% SP-525 for 48 bile acids and related compounds as their methyl ester acetate derivatives are given. Ion tables for electron impact spectra have been compiled that permit direct access to ion structures for any given ion mass.

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The formation of bile acids in man is thought to involve a series of reactions in which the initial steps are the same for both cholic acid and chenodeoxycholic acid. The point of bifurcation of the pathway is postulated to occur after the formation of 7alpha-hydroxy-4-cholesten-3-one. To test the hypothesis that the entire synthesis of both bile acids proceeds through this intermediate we studied the metabolism of labeled 7alpha-hydroxy-4-cholesten-3-one in eight normal subjects with an intact enterohepatic circulation.

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Chenodeoxycholic acid labeled with 2H in the 11 and positions was prepared by catalytic reduction of delta 11-12 unsaturated derivatives of cholic acid. To validate the use of this stable isotope for the determination of bile acid kinetics by isotope dilution, it was administered to seven normal male volunteers simultaneously with [24-14C]chenodeoxycholic acid. Bile was collected at regular intervals over the following 5 days, and the chenodeoxycholic acid pool size and fractional turnover rate were determined from the specific activity decay curve for 14C and from the isotopic abundance curve for 2H.

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Studies were carried out in a family in which two children with cholestasis due to intrahepatic bile duct anomalies were shown to have increased amounts of the cholic acid precursor, 3alpha, 7alpha, 12alpha-trihydorxy-5beta-cholestan-26-oic acid (THCA). The metabolism of THCA was studied in one of these patients after an intravenous injection of (3H)THCA, and the cause of the increased amounts of THCA in this condition was found to be due to a metabolic defect in the conversion of this compound into cholic acid. A small amount of (3H)cholic acid was also identified after (3H)THCA administration, confirming that this metabolic defect was incomplete.

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Bile salt synthesis and bile salt pool size were determined by isotope dilution in two groups of healthy premature infants, utilizing nonradioactive deuterium-labeled bile salts. All 9 infants were between 32 and 36 weeks of gestation; however, in one group (4 infants), the mothers had received either dexamethasone or phenobarbital prior to delivery. The total bile salt pool averaged 20 mg for the infants of untreated mothers and 79 mg for the infants of treated mothers; similarly, the bile salt synthesis of 8 mg per day in the untreated group was increased to 27 mg per day for the treated group.

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