Reinhard Kaindl

Design and synthesis of a novel cationic thiolated polymer

The purpose of this study was to design and characterize a novel cationic thiolated polymer. In this regard a hydroxyethylcellulose-cysteamine conjugate (HEC-cysteamine) was synthesized. Oxidative ring opening with periodate and reductive amination with cysteamine were performed in order to immobilize free thiol groups to HEC. The resulting HEC-cysteamine displayed 2035 ± 162 μmol immobilized free thiol groups and 185 ± 64 μmol disulfide bonds per gram of polymer being soluble in both acidic and basic conditions. Unlike the unmodified HEC, in case of HEC-cysteamine, a three-fold increase in the viscosity was observed when equal volumes of the polymer were mixed with mucin solution. Tablets based on HEC-cysteamine remained attached on freshly excised porcine mucosa for 8 0h and displayed increased disintegration time of 2h. Swelling behavior of HEC-cysteamine tablets in 0.1M phosphate buffer pH 6.8 indicated swelling ratio of 19 within 8h. In contrast, tablets comprising unmodified HEC detached from the mucosa within few seconds and immediately disintegrated. In addition, they did not exhibit swelling behavior. The transport of rhodamine 123 across freshly excised rat intestine enhanced by a value of approximately 1.6-fold (p-value = 0.0024) in the presence of 0.5% (m/v) HEC-cysteamine as compared to buffer control. Result from cytotoxicity test of HEC-cysteamine applied to Caco-2 cells in concentration of 0.5% (m/v) revealed 82.4 ± 4.60% cell viability. According to these results, HEC-cysteamine seems to be a promising polymer for various pharmaceutical applications especially for intestinal drug delivery.

Intermediate states on the way to edge-sharing BO4 tetrahedra in M6B22O39·H2O (M=Fe, Co).

The new borates Fe(II)(6)B(22)O(39)·H(2)O (colourless) and Co(II)(6)B(22)O(39)·H(2)O (dichroic: red/bluish) were synthesised under the high-pressure/high-temperature conditions of 6 GPa and 880 °C (Fe)/950 °C (Co) in a Walker-type multi-anvil apparatus. The compounds crystallise in the orthorhombic space group Pmn2(1) (Z=2) with the lattice parameters a=771.9(2), b=823.4(2), c=1768.0(4) pm, V=1.1237(4) nm(3), R(1)=0.0476, wR(2)=0.0902 (all data) for Fe(6)B(22)O(39)·H(2)O and a=770.1(2), b=817.6(2), c=1746.9(4) pm, V=1.0999(4) nm(3), R(1)=0.0513, wR(2)=0.0939 (all data) for Co(6)B(22)O(39)·H(2)O. The new structure type of M(6)B(22)O(39)·H(2)O (M=Fe, Co) is built up from corner-sharing BO(4) tetrahedra and BO(3) groups, the latter being distorted and close to BO(4) tetrahedra if additional oxygen atoms of the neighbouring BO(4) tetrahedra are considered in the coordination sphere. This situation can be regarded as an intermediate state in the formation of edge-sharing tetrahedra. The structure consists of corrugated multiple layers interconnected by BO(3)/BO(4) groups to form Z-shaped channels. Inside these channels, iron and cobalt show octahedral (M1, M3, M4, M5) and strongly distorted tetrahedral (M2, M6) coordination by oxygen atoms. Co(II)(6)B(22)O(39)·H(2)O is dichroic and the low symmetry of the chromophore [Co(II)O(4)] is reflected by the polarised absorption spectra (Δ(t)=4650 cm(-1), B=878 cm(-1)).

Incommensurate structure of Ca2Al2O5 at high temperatures – structure investigation and Raman spectroscopy

A high-temperature X-ray diffraction study revealed that brownmillerite-type Ca(2)Al(2)O(5) transforms to an incommensurately modulated structure at elevated temperatures. Single crystals of Ca(2)Al(2)O(5) were synthesized in an end-loaded piston cylinder press at 2.5 GPa and 1273 K. The diffraction pattern observed at 1090 (10) K by in situ single-crystal diffraction experiments can be indexed by an I-centred orthorhombic cell and a modulation wavevector of q = 0.595 (1)c(*). A (3 + 1)-dimensional model in superspace group Imma(00gamma)s00 was used to refine the modulated structure. The structure is assembled from two building units: (i) layers of corner-sharing [AlO(6)] octahedra, stacked along b alternate with (ii) layers of zweier single chains of [AlO(4)] tetrahedra running along a. The modulated structure arises from an aperiodic sequence of two different configurations of the chains within the tetrahedral layers. The modulated high-temperature phase of Ca(2)Al(2)O(5) is isotypic to the modulated high-temperature modification of Ca(2)Fe(2)O(5). A large hysteresis was found in the phase-transition temperature. On heating, the transition occurs at ca 1075 (10) K; on cooling, satellite reflections can be observed down to 975 (10) K. The characterization of Ca(2)Al(2)O(5) is completed by Raman spectroscopy, including a partial interpretation of the spectra.

Synthesis, Crystal Structure, and Vibrational Spectroscopy of K2Ca4Si8O21—An Unusual Single-Layer Silicate Containing Q2 and Q3 Units

Single crystals of the previously unknown potassium calcium silicate K2Ca4Si8O21 (1) have been grown from a nonstochiometric melt as well as using a KCl flux. The compound is triclinic with the following basic crystallographic data: space group P, a = 6.8052(3) A, b = 7.1049(3) A, c = 11.2132(5) A, alpha = 96.680(4)degrees, beta = 105.280(4) degrees, gamma = 109.259(4)degrees, Z = 1, V = 481.28(4) A3. The crystal structure was solved by direct methods based on a single-crystal diffraction data set collected at ambient conditions. From a structural point of view, K2Ca4Si8O21 belongs to the group of single-layer silicates. The layers parallel to (001) are characterized by a complex arrangement of 6-, 8-, 10-, and 12-membered tetrahedral rings. The sheets can be built from the condensation of loop-branched fnfer single chains running parallel to [100], i.e., the crystallochemical formula can be written as K2Ca4{lB,5, 1(infinity)2}[Si8O21]. Compound 1 is the first example of a loop-branched layer silicate containing secondary (Q2) as well as tertiary (Q3) tetrahedra. Linkage between the layers is provided by calcium and potassium cations, which are distributed among a total of three crystallographically independent nontetrahedral sites. Alternatively, the structure can be described as a heteropolyhedral framework, based on SiO4 tetrahedra and CaO6 octahedra. The irregularly coordinated K-cations in turn are incorporated in tunnels of the network running parallel to [110]. The structural investigations have been completed by Raman spectroscopy. The allocation of the bands to certain vibrational species has been aided by density functional theory (DFT) calculations.

Quantum-mechanical calculations of the Raman spectra of Mg- and Fe-cordierite

Abstract Quantum-mechanical calculations with a hybrid HF/DFT Hamiltonian (B3LYP) model yielded the Raman-active vibrational modes of the Mg- and Fe-cordierite structure. Maximum and mean deviation between experimentally derived bands and calculated modes of synthetic Mg- and natural Fe-rich cordierite are ±19 and 7 cm-1. Most of the observed bands could be related to specific vibrational modes of tetrahedral and octahedral sites of the cordierite structure, although the large number of Ramanactive modes (87) prevents a complete assignment. Atomic motions in cordierite are compared with those of the structurally similar mineral beryl. The calculations enable more accurate interpretation of the Raman spectra with respect to structural changes of cordierite, in particular Al-Si ordering and Mg-Fe exchange.

Oxidation and diffusion processes during annealing of AlCrVN hard coatings

V-alloyed AlCrN hard coatings were deposited by reactive arc evaporation in an industrial-sized deposition system and subsequently annealed in ambient air at temperatures ranging from 550to700°C in order to study the formation mechanisms of the desired lubricious oxides. The oxidized samples were investigated by means of secondary ion mass spectrometry depth profiling, x-ray diffraction, Raman spectroscopy, and analytical transmission electron microscopy. Vanadium diffusion in the oxidized part of the coating leads to the formation of a V-rich top layer containing AlVO4 and the desired lubricious oxide V2O5 followed by a V-depleted inner oxide layer consisting of a mixed or nanocrystalline (Al,Cr,V)2O3 on top of the intact AlCrVN coating.

A semi-quantitative technique for determination of CO2 in cordierite by Raman spectroscopy in thin sections

Confocal micro-Raman spectroscopic measurements at high spatial resolution of about 5 μm 3 were performed to determine the CO 2 contents of natural cordierite. Nine cordierite single-crystals with known CO 2 concentrations, previously determined by colorimetric titration, were studied to obtain a calibration curve for this method. Measurements were also performed to quantify the CO 2 content of cordierite porphyroblasts in a thin section of a granulite-facies metapelite from Kosseldorf, Sauwald Area, Southern Bohemian Massif, Upper Austria. Fifteen points along a traverse through a large (560 μm) single crystal revealed low CO 2 contents of 0.14 ± 0.11 wt.% CO 2 . These results provide some constraints on the activity of CO 2 [a(CO 2 )] during granulite-facies metamorphism, only if fluid-saturated conditions prevailed or independent H 2 O measurements were made.

A Murine Model of Phosphate Nephropathy

We established a murine model of phosphate nephropathy with secondary hyperparathyroidism. db/db mice, which develop obesity and type 2 diabetes mellitus, were uninephrectomized at the age of 6 weeks and were fed either standard chow or a phosphorus-rich diet during the next 8 weeks. Thereafter, renal cryosections showed abundant tubular casts with a strong histochemical von Kossa reaction in all db/db mice on the phosphorus-rich diet but none in the controls. X-ray diffraction and Raman spectroscopy proved that these tubular casts consist mostly of hydroxyapatite Ca₅(PO₄)₃(OH). These intraluminal precipitations were located in distal tubuli and collecting ducts and were associated with degenerative tubular changes and peritubular infiltration of T cells and macrophages. In line, kidneys of db/db mice on the phosphorus-rich diet displayed significantly increased mRNA expression of the T(H)1 cytokines interferon γ, IL-6, and tumor necrosis factor α. In addition, mice developed signs of secondary hyperparathyroidism as shown by elevated serum phosphate, decreased serum calcium, and increased parathyroid hormone, osteopontin, and fibroblast growth factor 23 levels. db/db mice on the phosphorus-rich diet also presented with significantly lower body weight, lower homeostasis model assessment of insulin resistance index, and hypertrophic cardiomyopathy. Thus, we provide a murine model of phosphate nephropathy and secondary hyperparathyroidism, which can be used for future pharmacologic and pathophysiologic studies to analyze the effect of hyperphosphatemia on renal, metabolic, and cardiovascular phenotypes.

The chemical composition of tetrahedrite-tennantite ores from the prehistoric and historic Schwaz and Brixlegg mining areas (North Tyrol, Austria)

The copper ore occurrences from Schwaz and Brixlegg were mined both in prehistoric and historic times. The ores occur as discordant veins, strata-bound bodies and breccias in the Devonian Schwaz Dolomite of the Northern Greywacke Zone. The ore mineral assemblage is characterized by more or less monomineralic Fe-Zn-Hg-bearing tetrahedrite-tennantite. Especially in the Groskogel mining area in Brixlegg, barite is associated with the tetrahedrite-tennantite ores. To characterize the compositional variations of tetrahedrite-tennantite a comprehensive electron microprobe investigation involving the analysis of 21 elements was conducted. The mining areas of Schwaz and Brixlegg can be distinguished by their chemical and mineralogical compositions. Whereas fahlore from Schwaz is a strongly zoned Fe-Zn tetrahedrite-tennantite solid solution (10.4 % to 59.8 % tennantite component, 21.8–71.8 % Zn end-member) with high Hg (≤5.56 wt%) and low Ag (≤0.80 wt%) concentrations, fahlore from Brixlegg, also strongly zoned, is generally richer in Zn (47.8–97.1 % Zn end-member) and poorer in Hg ( ≤2.11 wt%) with comparable low Ag concentrations. The mineralogical differences are basically due to the tetrahedrite-tennantite breakdown textures in ores from Brixlegg leading to the assemblage enargite/luzonite-famatinite + sphalerite + pyrite + stibnite + chalcostibite, or fahlore (second generation) + enargite/luzonite-famatinite +sphalerite +pyrite +stibnite +chalcostibite and fahlore (second generation) +sphalerite +pyrite +stibnite + chalcostibite. The following model reactions explaining these reaction assemblages can be proposed: Cu 10 Fe 2 Sb 4 S 13 + Cu 10 Fe 2 As 4 S 13 + 13 / 4 S 2 → 1 / 2 Cu 10 Fe 2 Sb 4 S 13 + 1 / 4 Cu 10 Fe 2 As 4 S 13 + 3 Cu 3 AsS 4 + Cu 4 SbS 4 + 1 / 2 CuSbS 2 + 1 / 4 Sb 2 S 3 + 5 / 2 FeS 2 Cu 10 Fe 2 Sb 4 S 13 + Cu 10 Fe 2 As 4 S 13 + 5 S 2 → 3 Cu 3 AsS 4 + 2 Cu 3 SbS 4 + 2 CuSbS 2 + 4 FeS 2 Cu 10 Zn 2 Sb 4 S 13 + Cu 10 Zn 2 As 4 S 13 + 2 S 2 → 1 / 2 Cu 10 Zn 2 Sb 4 S 13 + 1 / 4 Cu 10 Zn 2 As 4 S 13 + 3 Cu 3 AsS 4 + Cu 3 SbS 4 + 1 / 2 CuSbS 2 + 1 / 4 Sb 2 S 3 + 5 / 2 ZnS Cu 10 Zn 2 Sb 4 S 13 + Cu 10 Zn 2 As 4 S 13 + 3 S 2 → 4 Cu 3 AsS 4 + 2 Cu 3 SbS 4 + 2 CuSbS 2 + 4 ZnS Thermodynamic modelling of these breakdown reaction textures shows that either local-scale variations in sulphur fugacity , f S 2 , and/or decreasing temperature , T , result in the breakdown of the fahlores. The presented chemical and mineralogical data were subsequently compared to ore-fragments, copper slags and raw copper from mining archaeological excavations at the Kiechlberg Early Bronze Age copper smelting site near Innsbruck (Tirol, Austria). Excavated ore fragments contain tetrahedrite-tennantite with similar Fe-Zn-Hg concentrations and breakdown textures as described from the Brixlegg mining district. Several raw copper fragments also yielded similar high Sb-, As- and Ag-concentrations. These observations indicate 1) the use of fahlore-copper smelting and 2) local-scale import of copper-ore from Brixlegg.

Experimental determinations and quantum-chemical calculations of the vibrational spectra of β-ZnB4O7 and β-CaB4O7.

The two oxoborates β-ZnB4O7 and β-CaB4O7 were synthesized and investigated by FTIR- and Raman spectroscopy and ab initio quantum chemical calculations. Maximum and mean deviations between experimentally determined bands and calculated modes ranged between 15-36 cm(-1) and 5-7 cm(-1), respectively, allowing band assignments to vibrational modes in most cases. The complex network structures with tetrahedral BO4 and planar OB3 groups are mirrored by the spectra and numerous vibrational modes, not assignable by standard borates classification schemes. It was confirmed that OB3 units, despite similar force constants and geometry, do not absorb in the same range as BO3 units. Bands in the high wavenumber range are rather caused by B-O-(Zn/Ca), O-B-O, B-O-B, and B-O stretching and bending vibrations. The experimental observation of inactive or Raman-active modes in the absorption spectra indicates defects or structural distortions in both compounds.