Ordnung muss sein: heteroelement order and disorder in polyoxovanadates.

The first mixed antimonato-germanato polyoxovanadates were synthesized using two different strategies, highlighting the critical role of the precursors. Following the traditional route using multiple single sources as precursors the polyanions [V15Sb2Ge4O42(OH)4(H2O)]6- (1) and [V15Sb3Ge3O42(OH)3(H2O)]6- (2) are obtained, which display disorder of their Sb/Ge positions, indicating that clusters of different compositions are in equilibrium in solution. In contrast, if the water-soluble single-source precursor {Ni(en)3}3[V15Sb6O42(H2O)]·ca. 15H2O is reacted with GeO2, {Ni(en)3}3[V15Sb3Ge3O42(OH)3(H2O)]·≈9H2O (3) forms, in which Sb and Ge occupy distinct positions that might have been formed via partial substitution reactions in the {V15Sb6} precursor.

In situ ligand exchange-mediated 0D/1D transformation of a polyoxovanadate.

The antimonato-polyoxovanadate {NiII(en)3}3[VSbO42(H2O)]·ca.15H2O was utilized as a synthon for the solvothermal in situ generation of the new compound {NiII(phen)3}2[{NiII(en)2}VSbO42(H2O)]·19H2O, a rearrangement induced by ligand metathesis. While in the precursor structure cations and anions are isolated, the solid-state structure of the product is characterized by 1D chains consisting of alternating [V15Sb6O42(H2O)]6- cluster shells and [Ni(en)2]2+ units covalently linked to neighboring clusters via terminal oxygen atoms. Water clusters composed of sixteen hydrogen-bonded H2O molecules are located in void spaces of the structure. The magnetic properties indicate weak antiferromagnetic interactions of the bridging Ni2+ center and adjacent polyoxovanadate anions, as well as small magnetic anisotropy of the individual Ni2+ centers.

Utilization of mixtures of aromatic N-donor ligands of different coordination ability for the solvothermal synthesis of thiostannate containing molecules.

Utilization of mixtures of differently coordinating aromatic N-donor ligands leads to the formation of the two new compounds {[Ni(phen)2]2Sn2S6}·4,4'-bipy·½H2O I and {[Ni(phen)2]2Sn2S6}·2,2'-bipy II that could be prepared under solvothermal conditions (4,4'-bipy = 4,4'-bipyridine, C10H8N2; phen = 1,10-phenanthroline, C12H8N2; 2,2'-bipy = 2,2'-bipyridine, C10H8N2). In the structures of both compounds Ni-S bond formation is observed which is highly unusual when only bidentate N-donor ligands are applied in the reaction mixture. The detailed analysis of the crystal structure indicates that the presence of 4,4'-bipy and 2,2'-bipy molecules are essential for the stabilization of the arrangement of the constituents. The main structural motif {[Ni(phen)2]2Sn2S6} is arranged generating off center parallel stacking of the phen ligands. The empty spaces between the {[Ni(phen)2]2Sn2S6} moieties are occupied by either 2,2'-bipy (I) or 4,4'-bipy (II) molecules which are oriented towards the phen ligands to form intermolecular π-π interactions.

Thermoelectric efficiency of (1 - x)(GeTe) x(Bi2Se0.2Te2.8) and implementation into highly performing thermoelectric power generators.

Here we report for the first time on a complete simulation assisted "material to module" development of a high performance thermoelectric generator (TEG) based on the combination of a phase change material and established thermoelectrics yielding the compositions (1 - x)(GeTe) x(Bi(2)Se(0.2)Te(2.8)). For the generator design our approach for benchmarking thermoelectric materials is demonstrated which is not restricted to the determination of the intrinsically imprecise ZT value but includes the implementation of the material into a TEG. This approach is enabling a much more reliable benchmarking of thermoelectric materials for TEG application. Furthermore we analyzed the microstructure and performance close to in-operandi conditions for two different compositions in order to demonstrate the sensitivity of the material against processing and thermal cycling. For x = 0.038 the microstructure of the as-prepared material remains unchanged, consequently, excellent and stable thermoelectric performance as prerequisites for TEG production was obtained. For x = 0.063 we observed strain phenomena for the pristine state which are released by the formation of planar defects after thermal cycling. Consequently the thermoelectric performance degrades significantly. These findings highlight a complication for deriving the correlation of microstructure and properties of thermoelectric materials in general.

Electronic structure and magnetic properties of Mn1-xCrxSb alloys.

The electronic structure and magnetic properties of Mn1-xCrxSb alloys were investigated for the full concentration range. The stability of the concentration-dependent magnetic structure of the alloys were analysed on the basis of spin-spiral calculations as well as using the Monte Carlo (MC) simulations based on the Heisenberg model with the exchange coupling parameters calculated from first-principles. A leading contribution to the canted magnetic structure in Mn1-xCrxSb is the competition of the direct Cr-Cr and Mn-Mn exchange interactions having opposite signs. Furthermore, a strong impact of long-distance RKKY-type interactions is demonstrated. MC simulations at finite temperature were used to obtain the magnetic phase diagram for Mn1-xCrxSb alloys, which is in reasonable agreement with the experimental data.

Antimonato polyoxovanadate based three-dimensional framework exhibiting ferromagnetic exchange interactions: synthesis, structural characterization, and magnetic investigation of {[Fe(C6H14N2)2]3[V15Sb6O42(H2O)]}·8H2O.

The new polyoxovanadate {[Fe(C6H14N2)2]3[V15Sb6O42(H2O)]}·8H2O (1) was obtained under solvothermal conditions using the amine that acts at the same time as the ligand, solvent, and reducing agent. The central structural motif of 1, [V15Sb6O42(H2O)](6-), is related to the {V18O42}-archetype cluster by replacing three VO5 square pyramids with three O2Sb-O-SbO2 moieties. Every [V15Sb6O42(H2O)](6-) cluster anion is expanded by six FeN4O2 octahedra, thus generating a rare three-dimensional network with differently sized pores hosting the crystal water molecules. In 1, two [V15Sb6O42(H2O)](6-) cluster anions with different orientations coexist. According to bond-valence-sum calculations, the anionic cluster can be formulated as [V(IV)15Sb(III)6O42(H2O)](6-), i.e., in line with the valence states of all other known {V15Sb6} clusters. The optical band gap of 1 was determined as 2.47 eV. Investigation of the magnetic behavior indicates dominating ferromagnetic exchange interactions between the V(4+) centers of the cluster and the Fe(2+) d(6) cations.

Magnetic properties of CrSb compounds with zinc-blende and wurtzite structures.

The electronic structure and magnetic properties of Cr-Sb compounds with zinc-blende and wurtzite structure have been studied by means of the Korringa-Kohn-Rostoker (KKR) band structure method. The occurrence of a half-metallic behavior has been investigated for the bulk systems as a function of lattice parameter, as well as for thin films deposited on different substrates. In the latter case the influence of the surface and interface on the electronic structure is discussed in addition. To study magnetic order in the bulk and within the films, exchange coupling parameters have been calculated from first principles. They have been used for subsequent Monte Carlo simulations, based on a classical Heisenberg Hamiltonian, to obtain the Curie temperature.

Structural and magnetic properties of CrSb compounds: NiAs structure.

The structural and magnetic properties of CrSb compounds with NiAs structure have been studied by means of the Korringa-Kohn-Rostoker (KKR) band structure method. An analysis of the structural and magnetic stability has been performed on the basis of total energy calculations for various magnetic states. The magnetic properties at finite temperature have been investigated by means of Monte Carlo simulations on the basis of a classical Heisenberg Hamiltonian and the exchange coupling parameters calculated from first principles. This approach allowed us to determine the critical temperature in good agreement with experiment.

Finite-temperature magnetism of CrTe and CrSe.

An investigation on the electronic and magnetic properties of NiAs-type CrTe and CrSe has been performed for ferromagnetic, antiferromagnetic and non-collinear spin configurations, using the spin-polarized relativistic KKR (Korringa-Kohn-Rostoker) band structure method. Calculated exchange coupling parameters, as well as the total energy calculated as a function of the tilt angle of magnetic moments, indicate the presence of a non-collinear spin structure in CrTe and CrSe. The existence of a non-collinear spin structure is also shown by Monte Carlo (MC) simulations used for studies on the temperature dependent magnetization. The results are compared with available results in the literature and are in satisfactory agreement with the experimental results.

Syntheses and X-ray diffraction, photochemical, and optical characterization of Cu2SixSn1-xS3 (0.4 < or = x < or = 0.6) for photovoltaic applications.

The study of the pseudobinary system Cu(2)SnS(3-)Cu(2)SiS(3) shows that a solid solution (Cu(2)Si(x)Sn(1-x)S(3)) exists in the range 0.4 < or = Si/(Sn+Si) < or = 0.6. Based on diffuse reflectance and photoelectrochemical measurements these compounds show potential as absorber materials for photovoltaic devices. The compounds were prepared at 850 degrees C from copper sulfide, silicon, tin, and sulfur and were analyzed with single-crystal (for x approximately 0.40) and powder diffraction techniques. Optical band gaps of 1.25, 1.35, and 1.45 eV were observed for the three compositions x = 0.39, 0.48, and 0.61; cathodic photocurrent occurring is significant.

Effects of monomethyltin and dimethyltin compounds on heterologously expressed neuronal ion channels (Xenopus oocytes) and synaptic transmission (hippocampal slices).

The aim of this study was to investigate the effects of monomethyltin trichloride (MMT) and dimethyltin dichloride (DMT) on various neuronal ion channels heterologously expressed in Xenopus oocytes and on synaptic transmission in hippocampal slices of young (14-21 days old) and adult (2-4 months old) rats. The Xenopus oocyte expression system was chosen to allow direct assessment of the effects of MMT and DMT both on glutamate receptors sensitive to AMPA and NMDA and on various voltage-operated potassium and sodium channels. Hippocampal slices were used to analyze the effects of MMT and DMT on synaptic potentials generated by the important excitatory Schaffer collateral-CA1 synapse. In general, MMT and DMT were found to have no effect either on voltage-operated sodium and potassium channels or on the metabotropic glutamate receptor but they did differentially affect the functions of ionotropic glutamate receptors and glutamatergic synaptic transmission. MMT (100 microM) significantly reduced NMDA-mediated ion currents by up to 32%, but had no effect on ion currents through AMPA receptors. In slices of adult rats, MMT had no effect on the amplitudes of evoked fEPSPs and brought about a 35% reduction in the LTP amplitudes. In contrast, in slices of young rats MMT evoked a reversible 30% increase in the amplitudes of fEPSPs but had no effect on LTP induction. DMT (100 microM) reduced ion currents through NMDA-receptor ion channels by up to 29% and those through AMPA-receptor ion channels by up to 7%. In hippocampal slices 100 microM DMT reduced the amplitudes of fEPSPs (adults: 50%; young rats: 70%) and LTP (adults: 40%; young rats: 55%). Neither of the organotins affected the paired-pulse facilitation at this synapse, indicating that the organotins exert their effects at the postsynaptic site. The action of MMT and DMT may contribute to the organotin-induced impairment of behavior patterns in connection with learning and memory.

Template-assisted solvothermal synthesis of five copper(I)-thioantimonate(III) composites: crystal structures and optical and thermal properties of (C6N2H18)0.5Cu2SbS3, (C4N3H15)0.5Cu2SbS3, (C8N4H22)0.5Cu2SbS3, (C4N3H14)Cu3Sb2S5, and (C6)N4H20)0.5Cu3Sb2S5.

The novel copper(I)-thioantimonates(III) (C(6)N(2)H(18))(0.5)Cu(2)SbS(3) (I) (C(6)N(2)H(16) = 1,6-diaminohexane), (C(4)N(3)H(15))(0.5)Cu(2)SbS(3) (II) (C(4)N(3)H(13) = diethylenetriamine), (C(8)N(4)H(22))(0.5)Cu(2)SbS(3) (III) (C(8)N(4)H(20) = 1,4-bis(2-aminoethyl)piperazine), (C(4)N(3)H(14))Cu(3)Sb(2)S(5) (IV) (C(4)N(3)H(13) = diethylenetriamine), and (C(6)N(4)H(20))(0.5)Cu(3)Sb(2)S(5) (V) (C(6)N(4)H(18) = triethylenetetramine) were synthesized under solvothermal conditions reacting Sb, Cu, and S with the amines. The compounds I-III belong to the RCu(2)SbS(3) structure family (R = amine) and are built up of trigonal SbS(3) pyramids and two CuS(3) moieties forming 6-membered (6 MR) and 10-membered (10 MR) rings. The rings are condensed yielding single layers which are joined into [Cu(2)SbS(3)](-) double layers via Cu-S bonds. The organic ions are located between the anionic layers, and the shortest interlayer distances are 7.8 Angstroms (I), 7.4 Angstroms (II), and 8.8 Angstroms (III). The structure of the novel inorganic-organic hybrid compound IV contains one SbS(3) group, one SbS(4) unit, two CuS(3) triangles, and one CuS(4) tetrahedron. These units are joined into four-membered (4 MR) and six-membered rings (6 MR) forming a hitherto unknown strong undulated layered (Cu(3)Sb(2)S(5))(-) anion. Anions and cations are arranged in a sandwichlike manner with an interlayer distance of 6.184 A. The new composite V contains an anion with the same chemical composition as compound IV, but the structure exhibits a unique and different network topology which is constructed by two SbS(3) pyramids, two CuS(3) triangles, and one CuS(4) tetrahedron. These units are joined into 6 MR which may be described as an inorganic graphene-like layer or as a 6(3) net. Two such layers are connected via Cu-S bonds into the final double layer. The interlayer distance amounts to 6.44 Angstroms. All compounds decompose in a more or less complex manner when heated in an inert atmosphere.

RbCu2VS4.

The reaction of Cu and V in a Rb(2)S(5) melt yields black crystals of rubidium dicopper vanadium tetrasulfide, RbCu(2)VS(4). The structure is comprised of [Cu(2)VS(4)](-) layers within the (010) plane which are separated by Rb(+) cations. The layers consist of a network of edge- and corner-sharing [VS(4)] and [CuS(4)] tetrahedra parallel to (010). The optical band gap was determined as 1.45 eV.

Raloxifene and estrogen inhibit neointimal thickening after balloon injury in the carotid artery of male and ovariectomized female rats.

The effects of raloxifene and 17alpha-ethinyl estradiol (EE2) on intimal thickening in response to balloon injury were tested in male and ovariectomized female rats. In male rats, oral raloxifene and EE2, administered either by gavage or in the diet, inhibited arterial intimal thickening in response to balloon injury to a maximum of approximately 60 and 50%, respectively. The effect of oral raloxifene to decrease cholesterol was observed at doses (> or = 3 mg/kg/day) higher than those required to inhibit intimal thickening (> or = 0.03 mg/kg/day). Coadministration of the estrogen receptor antagonist, ICI 182,780 (5 mg/kg/day, s.c.), blocked the inhibition of balloon injury by raloxifene and EE2. Direct adventitial delivery of raloxifene (0.03 mg/kg/day) and EE2 (0.001 mg/kg/day) to the vascular wall inhibited intimal thickening by 63 and 53%, respectively. In ovariectomized female rats, oral raloxifene (0.01-3.0 mg/kg/day) and EE2 (0.08 mg/kg/day) inhibited intimal thickening to a maximum of 32 and 60%, respectively. Together, these data suggest that raloxifene and EE2, inhibit balloon arterial injury in the rat through direct effects on the vascular wall that involve the estrogen receptor and are at least partially independent of serum cholesterol.

Bis

The title double salt, [Ni(C(2)H(8)N(2))(3)](2)(SbS(4))(NO(3)), was crystallized under solvothermal conditions. Hydrogen bonds between the SbS(4)(3-) anions (at four sites) and the [Ni(en)(3)](2+) (en = ethylenediamine) cations (at two sites) form a three-dimensional network. The NO(3)(-) anion is disordered over four sites. The cation lies on a twofold rotation axis and the SbS(4)(3-) anion on a -4 axis.

Effects of LY295427, a low-density lipoprotein (LDL) receptor up-regulator, on LDL receptor gene transcription and cholesterol metabolism in normal and hypercholesterolemic hamsters.

The action of LY295427 [(3alpha,4alpha, 5alpha)-4-(2-propenylcholestan-3-ol)], a compound that derepresses low-density lipoprotein receptor (LDL-R) expression in a cell-based model, was examined in hamsters. It was found that the compound does not have an effect in normal chow-fed hamsters, in which LDL-R levels are not repressed, but exerts a marked hypocholesterolemic effect (>70% decrease) in cholesterol-coconut oil-fed hamsters, in which LDL-R is repressed. In this model, there is a dose-response for cholesterol lowering with an approximate ED50 value of 40 mg/kg/day and an inverse relationship between serum cholesterol and serum LY295427 levels. LDL-R mRNA is increased (2-fold) and liver cholesterol ester content is decreased (>90%). Unlike the 3-hydroxy-3-methylglutarylcoenzyme A reductase inhibitor lovastatin, the decreased serum cholesterol is confined to the non-high-density lipoprotein fraction. Furthermore, LY295427 does not affect cholesterol biosynthesis, and it does not have a significant effect on cholesterol absorption. These data suggest that LY295427 acts in the hypercholesterolemic hamster by derepressing LDL-R transcription, thereby enhancing cholesterol clearance from the blood. The results with LY295427 suggest that compounds that act to increase LDL-R may represent a novel approach in the pharmacotherapy for hypercholesterolemia.

Hypocholesterolemic activity of raloxifene (LY139481): pharmacological characterization as a selective estrogen receptor modulator.

After once-daily oral dosing in ovariectomized rats, raloxifene (LY139481) hydrochloride produced dose- and time-dependent reductions in serum cholesterol and high-density lipoprotein-cholesterol. Paired-feeding studies demonstrated that effects of raloxifene on serum lipids were not secondary to effects on food consumption. Maximal reductions in serum cholesterol occurred within 4 days of raloxifene administration or sooner, depending on the administered dose. The ED50 for 50% reduction in serum cholesterol by raloxifene was 0.13 +/- 0.04 mg/kg/day (mean +/- S.E.M., n = 17); maximal cholesterol reduction by raloxifene (68%) was significantly less than that produced by estrogen (17 alpha-ethinylestradiol; 89%) after 4 to 7 days of daily dosing. Dose-response curves for cholesterol lowering by raloxifene were generated in the presence of varying doses of 17 alpha-ethinylestradiol; two-way analysis of variance revealed significant interactions between estrogen and raloxifene with respect to cholesterol lowering (P < .001). Furthermore, a high dose of raloxifene (10 mg/kg/day) prevented further reduction of serum cholesterol by estrogen (1-100 micrograms/kg/ day) beyond that produced by raloxifene alone. For a series of closely related structural analogs of raloxifene, log(ED50) values for cholesterol lowering were highly correlated with log(relative binding affinity) for the estrogen receptor (r = 0.93; P < .0001). Thus, cholesterol lowering by raloxifene in ovariectomized rats is mediated primarily via partial agonist effects at estrogen receptors. Taken together with previous observations in uterine tissue of estrogen antagonism by raloxifene in the absence of significant agonism, the present findings support the classification of raloxifene as a selective estrogen receptor modulator.

Quantitative aspects of the desorption of copper from the silicon (100) surface.

The desorption of copper from copper contaminated Si(100) samples has been investigated by thermal desorption spectroscopy (TDS). The samples have been contaminated with aqueous CuSO(4)/EDTA solutions. The amount of copper deposited on the Si surface was in the monolayer region as determined by means of ratio-tracer experiments. The copper is adsorbed on the sample surface in two different states, which could be resolved by TDS. By means of STM and XPS measurements it was possible to assign these two desorption peaks to the desorption of copper from carbon deposits, which had already been present before the contamination process, and to the desorption of copper from the bare Si surface.

Synthesis and biological evaluation of a new series of sterols as potential hypocholesterolemic agents.

A new series of sterols was synthesized and tested in a CHO cell-based LDL receptor/luciferase (LDLR/Luc) assay to investigate the capability of derepressing the transcription of LDL receptor promoter in the presence of 25-hydroxycholesterol. The effect of various substitutions on antagonizing the repressing effect mediated by 25-hydroxycholesterol was also studied in terms of regio- and stereochemistry, lipophilicity, steric bulk, and pi-electron density. Except 12, compounds active in the primary LDLR/Luc assay were not active in the secondary simian virus 40/luciferase (SV40/Luc) assay, demonstrating the specificity of their in vitro activity. Eight active compounds of various structural types were selected and screened in a [1-14C-acetate]cholesterol biosynthesis inhibition assay; none has shown any interference with the cholesterol biosynthesis in CHO cells. In hypercholesterolemic hamsters, generally, compounds that were active in vitro were active in vivo and vice versa, with the exception of three in vitro inactive compounds: 3 beta-ols 3a' and 3c' as well as 3-ketone 2a. Experimental results from the livers of hamsters revealed that the in vivo conversion of 3a' or 2a to 3a has in part contributed to the observed in vivo activity, and it is also anticipated that 3c' may similarly be converted to 3c in hamsters.

Inhibition of cholesteryl ester transfer protein in normocholesterolemic and hypercholesterolemic hamsters: effects on HDL subspecies, quantity, and apolipoprotein distribution.

The effects of cholesteryl ester transfer protein (CETP) inhibition on the serum lipoprotein profile in both normocholesterolemic and hypercholesterolemic hamsters has been determined following subcutaneous injection of 12.5 mg/kg of the CETP neutralizing monoclonal antibody, TP2. Inhibition of CETP activity was greater than 60% and resulted in a 30-40% increase in high density lipoprotein (HDL) in both normal and hypercholesterolemic animals. These HDL effects were observed 1 day post-injection, were maximal by 4 days, and returned to control values by 14 days. Inhibition of CETP activity resulted in a decrease in both low density lipoprotein (LDL) and very low density lipoprotein (VLDL) cholesterol concomitant with HDL increase, and in hypercholesterolemic animals resulted in increased total serum cholesterol. In addition to the quantitative differences in LDL and HDL, there were significant increases in the size of the HDL, a shift to smaller LDL particles, and changes in apolipoprotein (apo) composition as evaluated by FPLC and Western blot analysis. Large apoA-I-poor and apoE-containing HDL became prevalent in hypercholesterolemic hamsters after CETP inhibition. In addition, the size of the CETP-containing HDL particles increased with inhibition of transfer activity. While these effects were apparent in normocholesterolemic animals, the changes in apolipoprotein distribution and HDL subspecies as detected on native gels were more significant in the hypercholesterolemic animals. The changes in the HDL profile and apolipoprotein distribution after CETP inhibition in hamsters were similar to those reported in CETP-deficient Japanese subjects, suggesting the utility of the hypercholesterolemic hamster as an in vivo model for the understanding of the lipoprotein changes associated with CETP inhibition.