Simulation model for shapiro time delay and light deflection experiments

The time delay experiment proposed by I.I. Shapiro in 1964 and conducted in the seventies was the most precise experiment of general relativity until that time. Further experimentation has improved the accuracy level of both the time delay and the light deflection experiments. A simulation model is proposed that involves only a simple mass and time transformation factor involving velocity of light. The light deflection and the time delay experiments are numerically simulated using this model that does not use the general relativistic equations. The computed values presented in this paper compare well with recent levels of accuracy of their respective experimental results.     

The reactions of tellurium tetrahalides with triphenylphosphine under ambient conditions

The reactions of tellurium tetrahalides and triphenylphosphine in tetrahydrofuran have been carried out under ambient conditions and afford [(Ph(3)PO)(2)H](2)[Te(2)X(10)] [X = Cl (1), Br (2)] and [(Ph(3)PO)(3)(OH(3)])(2)[TeI(6)] (4). The X-ray structures of 1 and 2 show that they are isostructural and contain discrete [Te(2)X(10)](2-) anions exhibiting octahedral coordination around both tellurium atoms with one shared edge and [Ph(3)POH...OPPh(3)](+) cations that show strong hydrogen bonds (the O...O distances are 2.399 and 2.404 A for 1 and 2, respectively). The compound 4 is built up with discrete octahedral hexaiodotellurate anions and [(Ph(3)PO)(3)(OH(3))](+) cations. The reaction of TeBr(4) and PPh(3) also results in the formation of formally zwitterionic Ph(3)PO(CH(2))(4)TeBr(4) (3). This reaction involves an unprecedented THF ring opening in which the oxygen atom becomes bonded to the phosphorus atom of triphenylphosphine and the carbon atom at the other end of the five-atomic chain becomes bonded to the tellurium atom of TeBr(4). The ring opening of the solvent THF is also taking place in the reaction involving tellurium tetraiodide, as indicated by the formation of C(4)H(8)TeI(2) (5). The reaction may initially lead to Ph(3)PI(2) that reacts with THF yielding Ph(3)PO and ICH(2)(CH(2))(2)CH(2)I. The latter species reacts with elemental tellurium producing 5. Depending on the conditions upon crystallization, two polymorphs of C(4)H(8)TeI(2) (5a and 5b) are observed. While the molecular structures of the two forms are virtually identical, their packing and intermolecular contacts are different. Two further minor products (6a and 6b) were isolated in the reaction of TeI(4) and PPh(3): Both are formally 1:1 adducts of 5 and TeI(4), but they differ considerably in their structures. 6a can be formulated as [C(4)H(8)TeI(+)](2)[Te(2)I(10)(2-)] and 6b as [C(4)H(8)TeI(+)](2)(TeI(3)(+))(2)(I(-))(4). The latter compound exhibits framework similar to that of the tetramers in gamma- and delta-TeI(4).     

A monomeric selenium(IV) diimide and a dimeric seleninylamine

The selenium(IV) diimide AdN=Se=NAd (Ad = 1-adamantyl) adopts a monomeric structure with a Z,E configuration in the solid state whereas the seleninylamine OSe(mu-NBut)2SeO crystallizes as the cis-dimer.     

MM-PBSA free energy analysis of endo-1,4-xylanase II (XynII)-substrate complexes: binding of the reactive sugar in a skew boat and chair conformation

The binding of xylotetraose in different conformations to the active site of endo-1,4-beta-xylanase II (XynII) from Trichoderma reesei was studied using molecular dynamics (MD) simulations and free energy analyses employing the MM-PBSA (Molecular Mechanics-Poisson-Boltzmann Surface Area) method. MD simulations of 1 ns were done for the substrate xylotetraose having the reactive sugar, which is bound in the -1 subsite of XynII in the 4C1 (chair) and 2So (skew boat) ground state conformations, and for the transition state of the XynII catalysed hydrolysis of the beta-glycosidic linkage. According to the simulations and free energy analysis, XynII binds the substrate with the -1 sugar in the 2So conformation 59.8 kJ mol(-1) tighter than the substrate with the sugar in the 4C1 conformation. The reactive 2So conformation resembles closely the reaction transition state and has the breaking glycosidic bond in a pseudo-axial orientation ready for facile bond cleavage. The transition state was calculated to be bound 77.1 kJ mol(-1) tighter than the 4C1 ground state conformation. The molecular mechanical interaction energy between the enzyme and the reactive pyranoside unit at the -1 subsite was 75.7 kJ mol(-1) more favorable for the binding of the 2So conformation than the 2C1 conformation, explaining the clearly tighter binding of the reactive structure The results of this study indicate that in the Michaelis complex XynII, a member of the family 11 xylanase, the substrate is bound in a skew boat conformation and in the catalytic reaction, the -1 sugar proceeds from the 4C1 conformation through 2So to the transition state with the -1 sugar in the 2,5B conformation.     

Applicability of microwave induced plasma optical emission spectrometry (MIP-OES) for continuous monitoring of mercury in flue gases

The applicability of microwave-induced plasma optical emission spectrometry (MIP-OES) for continuous monitoring of the environmentally hazardous element mercury in flue gases has been studied. Microwave induced plasmas have been sustained using both a TM₀₁₀ cavity (Beenakker resonator) and a so-called Surfatron. The analytical figures of merit for mercury in argon and helium discharges with both types of low-power micro-wave discharges have been examined. To determine mercury in artificial stack gases non-mixed argon/nitrogen discharges have been tested using a tangential flow torch design which allows to introduce a metal-loaded nitrogen gas flow as external gas and argon as internal gas. The addition of main flue gas components such as water vapour (concentration <6 g/m³), oxygen (<4% v/v) and carbon dioxide (<15% v/v) decrease the mercury line intensities to a considerable extent. Trace gases (CO, HCl, SO₂, NO) in concentrations typical to waste incineration processes have been found to have no effect on the mercury and the argon line intensities. The detection limit of mercury in nitrogen is 8 g/m³ using the TM₀₁₀ MIP and 10 g/m³ using the Surfatron. As such low detection limits are below the emission limit values of present-day environmental legislation MIP-OES is useful for on-line monitoring of mercury.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Chronopotentiometry in fused lithium chloride-potassium chloride

Previous work in the application of chronopotentiometry in aqueous and fused salt media has been reviewed. This investigation describes the application of this principle to the reduction of cadmium, cobalt, lead and thallium ions in a fused eutectic mixture of potassium, chloride and lithium. chloride at 450°C. Platinum microelectrodes of different areas and geometry were used. The transition time was limited to the order of 0.2 to 0.7 sec using oscillographic recording.It was found that so long as the dimensions of the electrode were considerably greater than the thickness of the diffusion, layer, linear diffusion theory was obeyed. The transition time constants for cadmium, cobalt, lead and thallium ions were found to be 0.83± 0.02, 0.90 ± 0.03, 0.95 ± 0.04, and 0.59 ± 0.02.10³ amp cm sec$\text{1}\text{2}$ per mole, respectively. The diffusion coefficients of these ions were calculated to be 2.08, 2.42, 2.18 and 3.88.IO^-5 cm² sec^-1, respectively.     

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.     

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.     

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.     

Cobalt complexes of a selenium diimide and a tellurium diimide dimer

[CoCl₂{N,N′-Te₂(N^tBu)₄}] (1) was obtained in good yields by the reaction of equimolar amounts of (^tBu)NTe(μ-N^tBu)₂TeN(^tBu) and CoCl₂ in toluene under an argon atmosphere. The crystal structure of 1·CH₂Cl₂ showed that the dimeric tellurium diimide ligand is N,N′-chelated to cobalt. The related reaction of Se(N^tBu)₂ and CoCl₂ affords a green product tentatively identified as a 1:1 adduct [CoCl₂{N,N′-Se(N^tBu)₂}] (CHN analysis). However, recrystallization from thf produces the ion-separated complex [Co₂(μ-Cl)₃{N,N′-Se(N^tBu)₂}₂(thf)₂][CoCl₃{NH₂(^tBu)}]·1½thf (2·1½thf), in which the monomeric selenium diimide ligand is N,N′-chelated to cobalt in the cation. A pathway for the formation of 2 from [CoCl₂{N,N′-Se(N^tBu)₂}] in thf is proposed.