Relaxation Dynamics and Magnetic Anisotropy in a Low‐Symmetry DyIII Complex

The magnetic behaviour of a Dy(LH)₃ complex (LH^? is the anion of 2‐hydroxy‐N′‐[(E)‐(2‐hydroxy‐3‐methoxyphenyl)methylidene]benzhydrazide) was analysed in depth from both theoretical and experimental points of view. Cantilever torque magnetometry indicated that the complex has Ising‐type anisotropy, and provided two possible directions for the easy axis of anisotropy due to the presence of two magnetically non‐equivalent molecules in the crystal. Ab initio calculations confirmed the strong Ising‐type anisotropy and disentangled the two possible orientations. The computed results obtained by using ab initio calculations were then used to rationalise the composite dynamic behaviour observed for both pure Dy^III phase and Y^III diluted phase, which showed two different relaxation channels in zero and non‐zero static magnetic fields. In particular, we showed that the relaxation behaviour at the higher temperature range can be correctly reproduced by using a master matrix approach, which suggests that Orbach relaxation is occurring through a second excited doublet.     

Characteristics and safety of nano-sized cellulose fibrils

A finely ground fibrillated cellulose was fractionated into separate size fractions. The characteristics of the smallest size fractions were studied, and the toxicity to humans was tested as part of a safety assessment. Morphological studies performed with state-of-the-art methods, such as scanning electron microscopy and atomic force microscopy, showed that the fraction obtained consisted of long thin fibrils but also larger fibril agglomerates, and spherical particles were present. The finest fraction did not show any sub-lethal effects as assessed by RNA inhibition test in vitro, nor were there any indications of genotoxicity as tested by the Ames test in vitro. Systemic effects tested in vivo with the nematode were also absent. No cytotoxic effects were seen in the highest tolerated dose test in vitro, but some indication of cytotoxicity was observed in the total protein content test in vitro at the highest sample concentration. The significance of this toxicity test result should be addressed in relation to the other toxicity tests, in which no toxicity was observed, with special emphasis on the in vivo test. Given this, the overall toxicity analyses support the conclusion that nano-scale cellulose fibrils can be considered to be safe towards humans. However, the reason for the positive cytotoxicity test result and, in addition, the effect of the biocide used in sample preservation on the toxicity tests need to be clarified before generalizing these results and declaring nanocellulose to be unambiguously safe.     

Highly Axial Magnetic Anisotropy in a N3O5 Dysprosium(III) Coordination Environment Generated by a Merocyanine Ligand

A spiropyran‐based switchable ligand isomerizes upon reaction with lanthanide(III) precursors to generate complexes with an unusual N₃O₅ coordination sphere. The air‐stable dysprosium(III) complex shows a hysteresis loop at 2 K and a very strong axial magnetic anisotropy generated by the merocyanine phenolate donor.     

Optical sensing of parameters crucial for Japanese woodblock print making

Traditional Japanese woodblock printing is a centuries old art form. This time-honoured form of art is at risk of extinction as a consequence of the increasing lack of availability of wild cherry trees, which are a traditionally used woodblock material. Solutions for this material problem have been investigated for several years, but none of the tested materials has been sufficient when compared with the watercolour print quality imprinted by wild cherry woodblocks. To contribute to overcoming this material problem, we have investigated the physical properties of heat-treated woodblock materials made from different wood species. The International Commission on Illumination (CIE) tristimulus values, the CIELAB coordinates, the total reflectance, and the gloss, as well as, the water contact angle from the woodblock surface is observed to have a strong relation to the surface treatment of a woodblock. The surface treatment of a woodblock, in turn, relates to its water delivery, which is the basis for watercolour printing.     

Adsorption of mercury on gold and silver surfaces

In order to study the adsorption mechanism of Hg on Au and Ag substrates, thin film Au(111) and Ag(111) substrates were exposed to gaseous metallic mercury, while the mercury concentration, substrate temperature, and exposure length were varied. The resulting changes in the surface morphology of the substrates were studied with scanning tunneling microscopy (STM). The amount of adsorbed Hg required to cause saturation, i.e. a decrease in the adsorption rate was found to be dependent on the mercury concentration and substrate temperature. The observations lead to the conclusion that the adsorption includes place exchange processes and concerted adsorption of more than one Hg atom in one process. The results show that the collection efficiency of single-crystalline surfaces is a function of both mercury concentration and temperature. Therefore, results from measurements performed at different conditions using single-crystalline surfaces may not be comparable. Received: 3 February 1999 / Revised: 7 June 1999 / Accepted: 9 June 1999     

A Selenium‐Nitrogen Chain with Selenium in Different Oxidation States

The reaction of tBuNH₂ with a mixture of SeCl₂ and SeOCl₂ in a 6:2:1 molar ratio produces the novel selenium‐nitrogen chain ClSeN(tBu)Se(O)Cl ( 4 ), in which the selenium atoms are in two different oxidation states, Se^II and Se^IV. The crystal structure of 4 is compared with that of the related Se^II/Se^II system ClSeN(tBu)SeCl ( 1 ) and differences are attributed to hyperconjugative effects. The energetics of the formation of 4 via two different routes are elucidated by PBE0/def2‐TZVPP calculations.     

1,3,5,7‐Tetraselena‐2,4,6,8(2,5)‐tetrathiophenaoctaphane

The novel title tetraselenacalix[4]arene, C₁₆H₈S₄Se₄ or [(C₄H₂S)Se]₄, has a centrosymmetric cyclic molecular structure with approximate C_2h molecular symmetry. The four thienyl rings are joined together by Se bridges and exhibit a syn–syn–anti–anti arrangement around the mol­ecule. The lattice consists of skewed stacks of mol­ecules, with chalcogen–chalcogen close contacts binding the stacks together, forming a two‐dimensional network of mol­ecules.     

URB754 has no effect on the hydrolysis or signaling capacity of 2-AG in the rat brain

Previous studies indicate that in brain tissue the endocannabinoid 2-AG is inactivated by monoglyceride lipase (MGL)-catalyzed hydrolysis, and a recent report has indicated that MGL activity could be specifically inhibited by URB754 . In the present study, URB754 failed to inhibit 2-AG hydrolysis in rat brain preparations. In addition, brain cryosections were employed to assess whether URB754 could facilitate the detection of 2-AG-stimulated G protein activity. Nevertheless, whereas pretreatment with PMSF readily allowed detection of 2-AG-stimulated G protein activity, URB754 was ineffective. In contrast to previous claims, brain FAAH activity was also resistant to URB754. Thus, in our hands URB754 was not able to block the endocannabinoid-hydrolyzing enzymes and cannot serve as a lead structure for future development of MGL-specific inhibitors.