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Biomedical subjects

N Piślewski

Publications and source records attributed to N Piślewski.

13 recordsLinked to original sources
PubMed1999

Proton magnetic resonance microimaging of human trabecular bone.

Proton magnetic resonance (1H magnetic resonance imaging (MRI)) images of human trabecular bone were acquired and discussed for two samples with different porosity. Three-dimensional 3D Spin Echo (3D SE) and Multi-Slice Multi-Echo (MSME) pulse sequences were examined. A very high slice resolution of (38 microm)2 was achieved (MSME). The intensity histograms were found useful for the characterization of the bone porosity. A spatial distribution of the spin-spin relaxation time T2 was monitored with the MSME pulse program. The work demonstrates the great potential of the proton MRI technique in the study of the trabecular bone morphology.

Bone and Bones↗
PubMed1998

1H NMR study of natural and partially deuterated ammonium hexachlorotellurate.

The proton spin-lattice relaxation times in natural and partially deuterated ammonium hexachlorotellurate have been measured. At high temperature (above 50 K) the relaxation curve reveals the classical, hindered reorientation of the ammonium ion with the same activation energy for all studied samples Ea = 5.6 kJ/mol. Below 50 K, the minima which appear in the T1 temperature dependencies are related to the level-crossing. The tunnelling splitting of the ground torsional level in isotopic pure ammonium hexachlorotellurate is equal to 55 MHz and increases with increasing deuteron concentration, due to the phase transitions occurring in partially deuterated crystal. The lowest temperature minimum in isotopic pure (NH4)2TeCl6 can be interpreted as a result of the rigid ammonium ion's reorientation about the threefold crystallographic axis. The limited jumps of NH4+ are characterised by the angle delta = 4 degrees between the NH bond and [111] direction.

Cold Temperature↗
PubMed1997

A nuclear magnetic resonance study of molecular motion in solid tris (n-propylammonium) enneachlorodiantimonate (III) (n-C3H7NH3)3Sb2Cl9.

Proton magnetic resonance second moment and spin-lattice relaxation time were carried out on polycrystalline tris (n-propylammonium) enneachlorodiantimonate (III), (n-C3H7NH3)3Sb2Cl9, in the temperature range of 10-370 K. The second moment measurements show that the structure is not rigid on the NMR scale at 10 K, the lowest temperature studied, and that CH3 and NH3 groups execute rotations about C3 axis. The proton spin-lattice relaxation measurements reveal two minima due to the motions of the amino and methyl groups. Analysis of the relaxation data yields the activation energy barriers of 11.0 kJ mol(-1) and 5.8 kJ mol(-1), respectively, for the NH3 and CH3 groups' motion. NMR data confirm the phase transition at Tc = 232 K, known from different studies.

Magnetic Resonance Spectroscopy↗
PubMed1996

1H NMR studies of molecular dynamics in polycrystalline catecholamines.

The proton dynamics in phenylephrine hydrochloride, isoprenaline hydrochloride and norephedrine hydrochloride have been monitored by measuring the temperature dependence of the 1H spin-lattice relaxation times. The results are interpreted as due to C3-hindered reorientation of the NH3 and CH3 groups. The activation parameters have been determined.

Catecholamines↗
PubMed1995

Molecular motions in solid [N(CH3)2H2]3Sb2I9 studied by proton nuclear magnetic resonance spectroscopy.

Molecular motions and phase transition in [N(CH3)2H2]3Sb2I9 was studied by measuring the temperature dependencies of the proton spin-lattice relaxation times T1 and the second moment M2. The results are interpreted in terms of the C'3 reorientation of the methyl groups and the whole cationic reorientation about the C2 axis. The activation parameters for these motions have been determined. The phase transition has no influence on the M2 and the T1 values, thus suggesting that it is not directly connected to the motion of the cation but rather to the dynamics of the inorganic subsystem [Sb2I9]3-.

Antimony↗
PubMed1995

Nuclear magnetic resonance proton dynamics study of [N(CH3)2H2]3Bi2I9 at low temperature.

The phase transitions of dimethylammonium nonaiododibismuthate [N(CH3)2H2]3Bi2I9 were studied by investigating the temperature dependence of the line widths and proton spin-lattice relaxation times in the nuclear magnetic resonance spectrum. Two phase transitions appeared to be connected with motions of the cationic and CH3 group in the molecule, while the third one seemed to be connected with the dynamics of the Bi2I9 group.

Cold Temperature↗
PubMed1995

Proton dynamics in solid noradrenaline hydrochloride.

The temperature dependencies of the proton spin-lattice relaxation times and second moment of the 1H nuclear magnetic resonance line have been measured for noradrenaline hydrochloride. Two symmetric minima of T1 are observed. They can be explained in terms of reorientation of the ammonium groups and proton transfer in the hydrogen bond. The activation parameters have been determined.

Hydrogen Bonding↗
PubMed1994

Molecular motions and phase transitions in solid bis-n-propylammonium pentabromoantimonate.

The proton nuclear magnetic resonance (NMR) second moment and spin-lattice relaxation time for polycrystalline bis-n-propylammonium pentabromoantimonate (nPBA) have been measured from 70 to 290 K. The results are interpreted in terms of the CH3 and NH3 group reorientations for which the activation parameters have been determined. A structural phase transition evidenced at about 220 K is found in the polycrystalline sample of nPBA.

Antimony↗
PubMed1994

Proton dynamics in solid dopamine and noradrenaline hydrochloride.

Proton spin-lattice relaxation times (T1) have been measured as a function of temperature for the following catecholamines: dopamine hydrochloride and adrenaline hydrochloride. For both substances a single symmetric minimum of T1 is observed which can be explained as a result of NH3 (dopamine) and CH3 (adrenaline) reorientation around the three-fold axis of the C-N bond. The activation parameters have been determined.

Dopamine↗
PubMed1993

Molecular dynamics of the methylammonium cation in [CH3NH3]5Bi2Cl11.

The 1H relaxation times T1 of methylammonium in chlorobismuthate(III) were measured in the temperature range from 50 to 270 K with a SXP 4/100 Bruker pulse spectrometer at 55.2 MHz. It was found that the T1 temperature dependence has three minima. The individual relaxation rates of the three-proton groups can be described by the O'Reilly and Tsang formula. The results obtained from the fitting procedure, using the typical Woessner formula for complex compounds, allow to conclude that the low-temperature minimum is due to the relaxation of all CH3 groups and the other two minima are due to the relaxation of two and four NH3 groups, respectively. This assignment is based on the X-ray results showing that methylammonium cations are differently bonded in this crystal.

Cations↗
PubMed1985

A study of the freezing of water in human uterine muscle by proton magnetic resonance.

Human uterine muscle and its nuclear fractions have been studied by means of nuclear magnetic resonance at temperatures from 300 degrees K to 143 degrees K. Different proton populations have been detected above and below the freezing point. On this basis it is suggested that the freezing of water in uterine muscle starts at the cell nuclei.

Body Water↗