Search

The first density functional theory based calculations of NMR shielding parameters for a transition metal nucleus is presented using periodic boundary conditions. It is demonstrated that principal components of the shielding tensors should be considered for the correlation between calculated and experimental results.

We report an initial magnetic study of highly crystalline nanoparticles of the layered-kagome compound BaCo3(VO4)2(OH)2. Quasi-spherical nanoparticles with size in the range of 9–25 nm were elaborated for the first time via a new synthetic route at ambient pressure. Rietveld refinement of X-ray diffraction data, vibrational spectroscopies and high-resolution scanning transmission electron microscopy indicates that the rhombohedral crystal structure of BaCo3(VO4)2(OH)2 is not modified by nanostructuring. Magnetisation measurements are consistent with high-spin Co2+ ions for which unquenched orbital angular momentum is present. Temperature-dependent magnetic susceptibility shows no apparent magnetic ordering or spin freezing down to 2 K and suggests finite-size or surface effects at low temperatures. [ABSTRACT FROM AUTHOR]

An optical study is presented of a series of In(As,P)/InP quantum wells grown using gas source molecular beam epitaxy.

Calorimetry, reflectivity and magnetism techniques were used for analyzing the transition temperature modifications with tungsten substitution. Findings reveal a significant increase in the temperature transition in a parallel way for the heating and cooling mode on substitution of molybdenum for tungsten.

A series of triazole fluoride weberites (M1−x2+Mx3+)M3+F5(Htaz)1−x(taz)x is obtained by hydrothermal synthesis. All phases are found to be isostructural to ZnAlF5(Htaz) by powder X-ray diffraction. Weberite structures are prone to induce the magnetic frustration of antiferromagnetic interactions originating from the cationic topology of HTB layers. The (nD) magnetic properties of (0D) Co–Ga, (1D) Zn–Fe, (3D) Fe–Ga, Mn–Fe, Co–Fe and Co–V couples are thus reported. Co2+ or Fe2+ magnetic anisotropy induces a negative magnetisation below TN and compensation temperatures for Mn–Fe and Co–Fe couples. All iron 3D magnetic phases exhibit high Néel temperatures, between 81 K and 102 K, and large ☋ϑP/TN☋ ratios, signalling strong magnetic frustration. Their cation site occupancies and the deduced (de)protonation states of the amine are accurately determined by 57Fe Mössbauer spectrometry. In addition, this spectroscopy evidences a subtle effect of the atmosphere that surrounds the samples: the magnetic ordering temperatures TN decrease significantly when the samples are cooled under vacuum with respect to samples that are cooled at ambient pressure. This novel phenomenon, which is highlighted for all studied (3D) triazole iron weberites, is reversible, and thus provides promising perspectives for understanding the underlying mechanism. [ABSTRACT FROM AUTHOR]

The hyperfine structure of the low-temperature Mössbauer spectra of dopant 119Sn4+ ions (0.4 at. %) in a fine crystalline MnO sample, characterized by X-ray diffraction and magnetic measurements, has been studied. The 119Sn spectra show that tin is distributed over positions with an inhomogeneous cationic environment. The appearance of such positions is explained by the local compensation for the excess charge of Sn4+ by manganese vacancies V Mn and segregation of defects resulting in precipitation of MnSnO3 clusters. The non-uniform distribution of Sn4+ and the related dependence of the number of broken magnetic bonds on the local tin concentration are responsible for the fluctuation of the T N values, which is “perceived” by 119Sn in different MnO crystallites. The 119Sn spectra exclude the possibility that tin enters into the composition of superpara-magnetic particles. [ABSTRACT FROM AUTHOR]

As valpromide is a prodrug of valproic acid (valproate), the clinical presentation of overdoses with either valpromide or valproate sodium is generally considered similar. Whereas plasma peak levels and signs of central nervous system depression occur within a few hours after the acute ingestion of regular-release forms of valproate sodium, delayed toxicity and time to peak levels following valpromide ingestion can be seen as shown by the three reported cases. They were initially considered as mild because patients presented with no or only moderate symptoms and serum valproate levels were below or at therapeutic levels on admission more than 3 hours post-ingestion in two of the three patients. Serum valproate levels were not monitored until marked deterioration more than 10 hours after ingestion. At the time of deterioration, serum valproate was at toxic level in the three reported cases. Therefore, large intake of valpromide should be closely monitored because no or moderate symptoms together with low plasma levels in the first few hours after ingestion do not exclude a subsequent severe intoxication. Despite the usual favourable outcome and the poor correlation between plasma levels and toxic symptoms, patients should not be discharged until plasma levels are documented to remain at low levels for at least 10 hours after the ingestion of valpromide and the patient asymptomatic. [ABSTRACT FROM AUTHOR]

The association between paracetamol overdose and prolonged prothrombin time due to hepatic failure is well recognized. However, little is known of the possibility that paracetamol overdose can prolong the prothrombin time without overt hepatic failure. The few data from the literature suggest this is either due to a reduction in the functional levels of the vitamin K-dependent clotting factors by elevated doses of paracetamol, or a consequence of the administration of the antidote N-acetylcystein. The three reported cases provide further evidence that paracetamol overdose can be associated with a prolongation in the prothrombin time without overt hepatic failure. Even though the prothrombin time provides useful prognosis information, decisions regarding the management of these patients should not solely be based on this endpoint to avoid misinterpretation of the accuracy and the severity of liver failure. [ABSTRACT FROM AUTHOR]

We make a new proposal to describe the very low temperature susceptibility of the doped Haldane gap compound Y2BaNi1-xZnxO5. We propose a new mean field model relevant for this compound. The ground state of this mean field model is unconventional because antiferromagnetism coexists with random dimers. We present new susceptibility experiments at very low temperature. We obtain a Curie-Weiss susceptibility χ( T ) ∼ C /(Θ + T ) as expected for antiferromagnetic correlations but we do not obtain a direct signature of antiferromagnetic long range order. We explain how to obtain the “impurity” susceptibility ( T ) by subtracting the Haldane gap contribution to the total susceptibility. In the temperature range [1 K, 300 K] the experimental data are well fitted by T ( T ) = C imp 1 + T imp / T . In the temperature range [100 mK, 1 K] the experimental data are well fitted by T ( T ) = A ln( T / T c ), where T c increases with x. This fit suggests the existence of a finite Néel temperature which is however too small to be probed directly in our experiments. We also obtain a maximum in the temperature dependence of the ac-susceptibility ( T ) which suggests the existence of antiferromagnetic correlations at very low temperature. [ABSTRACT FROM AUTHOR]

Summary: Severe but regressive toxic liver damage was observed in a 30-week pregnant woman due to acetaminophen poisoning. A cesarean section was performed 1 week later for suspected chorioamniotitis and the patient gave birth to an infant who only experienced complications of preterm birth. The lack of fetal liver damage following acute maternal paracetamol poisoning seems to be the rule, as shown by a review of the literature. [ABSTRACT FROM AUTHOR]