CoSm(SeO3)2Cl,CuGd(SeO3)2Cl,MnSm(SeO3)2Cl,CuGd2(SeO3)4 und CuSm2(SeO3)4: Übergangsmetallhaltige Selenite von Samarium und Gadolinum

CoSm(SeO₃)₂Cl, CuGd(SeO₃)₂Cl, MnSm(SeO₃)₂Cl, CuGd₂(SeO₃)₄ and CuSm₂(SeO₃)₄: Transition Metal containing Selenites of Samarium and Gadolinum The reaction of CoCl₂, Sm₂O₃, and SeO₂ in evacuated silica ampoules lead to blue single crystals of CoSm(SeO₃)₂Cl (triclinic, , Z = 4, a = 712.3(1), b = 889.5(2), c = 1216.2(2) pm, α = 72.25(1)°, β = 71.27(1)°, γ = 72.08(1)°, R_all = 0.0586). If MnCl₂ is used in the reaction light pink single crystals of MnSm(SeO₃)₂Cl (triclinic, , Z = 2, a = 700.8(2), b = 724.1(2), c = 803.4(2) pm, α = 86.90(3)°, β = 71.57(3)°, γ = 64.33(3)°, R_all = 0.0875) are obtained. Green single crystals of CuGd₂(SeO₃)₂Cl (triclinic, , Z = 4, a = 704.3(4), b = 909.6(4), c = 1201.0(7) pm, α = 70.84(4)°, β = 73.01(4)°, γ = 70.69(4)°, R_all = 0.0450) form analogously in the reaction of CuCl₂ and Gd₂O₃ with SeO₂. CoSm(SeO₃)₂Cl contains [CoO₄Cl₂] octahedra, which are connected via one edge and one vertex to infinite chains. The Mn²⁺ ions in MnSm(SeO₃)₂Cl are also octahedrally coordinated by four oxygen and two chlorine ligands. The linkage of the polyhedra to chains occurs exclusively via edges. Both, the cobalt and the manganese compound show the Sm³⁺ ions in eight and ninefold coordination of oxygen atoms and chloride ions. In CuGd(SeO₃)₂Cl the Cu²⁺ ions are coordinated by three oxygen atoms and one Cl^— ion in a distorted square planar manner. One further Cl^— and one further oxygen ligand complete the [CuO₃Cl] units yielding significantly elongated octahedra. The latter are again connected to chains via two common edges. For the Gd³⁺ ions coordination numbers of ?8 + 1”? and nine were found. Single crystals of the deep blue selenites CuM₂(SeO₃)₄ (M = Sm/Gd, monoclinic, P2₁/c, a = 1050.4(3)/1051.0(2), b = 696.6(2)/693.5(1), c = 822.5(2)/818.5(2) pm, β = 110.48(2)°/110.53(2)°, R_all = 0.0341/0.0531) can be obtained from reactions of the oxides Sm₂O₃ and Gd₂O₃, respectively, with CuO and SeO₂. The crystal structure contains square planar [CuO₄] groups and irregular [MO₉] polyhedra.     

Interior Layers for Second-Order Singular Equations

Our aim in this article is to study singularly perturbed problems which display boundary layers in the interior of the domain. These interior boundary layers which supplement the usual boundary layers at the boundary, are generated by discontinuities in the data. Second-order linear elliptic one-dimensional and multi-dimensional problems are considered in this article.     

Host–guest system of etodolac in native and modified β-cyclodextrins: preparation and physicochemical characterization

Etodolac, being a practically insoluble candidate, exhibits certain toxic effects and a limited bioavailability. Upon chronic use, it causes gastro-intestinal injury and increases the risk of ulcer complications. The approach of this study was to improve the physicochemical properties of the drug utilizing complexation phenomenon with β-, methyl-β- and hydroxypropyl-β-cyclodextrins, which may enhance the aqueous solubility and dissolution rate of etodolac, in an effort to increase oral bioavailability. In certain instances, this approach can be used to increase drug solubility, improve organoleptic properties and maximize the gastrointestinal tolerance by reducing drug irritation after oral administration. Differential UV measurements as well as continuous variation plots revealed the formation of equimolar complex with hydroxypropyl-β-cyclodextrin and 1:2 complexes with β-cyclodextrin and its methyl derivative. Differential scanning calorimetry (DSC), X-ray and FT-IR measurements were applied to prove inclusion complex formation and characterize the complexes. These results lend support to the idea that solubilization of etodolac is mainly related to inclusion complex formation and to a lesser extent to cyclodextrin aggregates. Understanding the factors that influence the performance of etodolac, will allow us to state that molecular encapsulation of the drug and other modifications with appropriate hydroxylation or methylation of parent β-cyclodextrin is able to overcome its problems and facilitate safe and efficient delivery of the drug.     

AC electrical properties study and equivalent circuit of a monovalent-mixed pyrophosphate

NaAgPbP₂O₇ was prepared with a solid-state reaction. The electrical properties were investigated by using impedance measurements in the frequency range from 200 Hz to 5 MHz with the TEGAM 3550 ALF automatic bridge monitored by a microcomputer between 581 K and 703 K. The Z′ and Z″ versus frequency plots are well fitted to an equivalent circuit model. The conductivity data obey the universal power law. The conductivity in the material is due to the hopping of monovalent ions parallel to (001) plane.     

How the cross-sectional discontinuity between ear canal and probe affects the ear canal length estimation

Many ear canal probes both deliver and measure sound via narrow tubes. This study investigates the effect of the cross-sectional discontinuity at the interface between ear canal models and the connecting tubes of a commercially available otoacoustic emission probe on the "acoustically" estimated cavity lengths. Rigid cavities having the same length but different diameters were produced, and modeled by the finite element method. Cavities with a diameter larger than 8 mm had acoustic lengths that considerably overestimated the real geometry. A length correction was derived, which, in most applications, compensates for the measurement errors emerging from the discontinuity effects.     

Nd5(AsO3)4Cl3: The First Oxo‐Arsenate(III)‐Chloride of the Lanthanides

Single crystals of Nd₅(AsO₃)₄Cl₃ (monoclinic, P2/n, Z = 2, a = 1026.0(1), b = 543.35(3), c = 1400.2(1) pm, β = 93.48(1)°) were obtained from the reaction of Nd₂O₃, As₂O₃ and NaCl in a sealed silica ampoule. In the crystal structure the Nd³⁺ ions are linked by AsO₃^3? groups into layers that alternate with layers of Cl^? ions. Two of the three crystallographically different Nd³⁺ ions are coordinated by eight oxygen atoms, the third one has four oxygen and four chlorine atoms as neighbours.     

Otoacoustic emission retrograde standing waves caused by eartip foams

Travelling the retrograde path from the inner ear towards the entrance of the ear canal, otoacoustic emissions (OAE) are apt to be affected by the impedance of the eartip foam. Therefore, the purpose of this study was to determine the complex reflection coefficient at the surface of eartip foam specimens. This was carried out by means of a conventional impedance tube. Measurements were performed with a closed end as well as with an open end behind the eartip foam, the latter configuration being considered as a more realistic analogy to the in-situ performance of eartips. For both configurations of the impedance tube, a high reflection coefficient of the foam was measured, representing an acoustically rigid boundary. Retrograde OAE standing waves are, hence, anticipated when modelling the path taken by the OAE signals. These retrograde standing waves would result in an OAE node near the tympanic membrane at the quarter-wavelength frequencies of the ear canal, rendering the measurements inaccurate at that location. Recording OAEs at the entrance of the ear canal is thus preferable. Moreover, the compression of the foam eartips, evaluated using a specially designed foam specimen, proved to have no significant effect on the reflection coefficient.