Thermoelasticity of ice explains widespread damage in dripstone caves during glacial periods.

Damage to speleothems is a common phenomenon in mid-latitude caves, and multiple causes have been proposed. Here we report on one of such type of damage, namely stalagmites that are broken and partially sheared near their base but are still in upright position. Such stalagmites occur in the Obir Caves (Austria) associated with cryogenic cave carbonates, demonstrating the former presence of cave ice. 230Th dating suggests damage to the speleothems during the Last Glacial Maximum. Numerical modelling combined with laboratory measurements demonstrates that internal deformation within a cave ice body cannot fracture stalagmites, even on a steep slope. Instead, temperature changes lead to thermoelastic stresses within an ice body that reach values equaling to and exceeding the tensile strength of even large stalagmites. Differences in thermal expansion coefficients cause a sharp vertical jump in stress between the stalagmite and the surrounding ice body, and the ice lifts the stalagmite as it expands with increasing temperature. This study refutes the previously accepted model that flow of ice breaks stalagmites, and suggests a link between glacial climate variability and corresponding cooling and warming cycles in the subsurface that weaken and eventually fracture stalagmites due to the opposing thermoelastic properties of calcite and ice.

La3 B6 O13 (OH): The First Acentric High-Pressure Borate Displaying Edge-Sharing BO4 Tetrahedra.

La3 B6 O13 (OH) was obtained by a high-pressure/high-temperature experiment at 6 GPa and 1673 K. The compound crystallizes in the space group P21 (no. 4) with the lattice parameters a=4.785(2), b=12.880(4), c=7.433(3) Å, and ß=90.36(10)°, and is built up of corner- as well as edge-sharing BO4 tetrahedra. It represents the first acentric high-pressure borate containing these B2 O6 entities. The compound develops borate layers of "sechser"-rings with the La3+ cations positioned between the layers. Single-crystal and powder X-ray diffraction, vibrational and MAS NMR spectroscopy, second-harmonic generation (SHG) and thermoanalytical measurements, as well as computational methods were used to affirm the proposed structure and the B2 O6 entities.

Synthesis and Characterization of the Tin Iodide Borate Sn3[B3O7]I.

The tin iodide borate Sn3[B3O7]I was synthesized via a hydrothermal synthesis and crystallizes in the centrosymmetric space group Pbca (no. 61) possessing lattice parameters of a = 1071.8(3), b = 852.3(2), and c = 2016.8(5) pm and Z = 8. Characteristic for the structure are infinite chains along the b axis, built up of three membered B3O8 rings consisting of one BO3 unit and two corner-sharing BO4 tetrahedra. The three tin cations are oriented differently: one cation is located layer-like between the infinite chains, and the other two cations show an orientation in a row with the infinite chain. In this structure, only one of the three tin cations exhibits a coordination to the halogen anion. The new centrosymmetric tin iodide borate Sn3[B3O7]I was investigated by single-crystal diffraction, vibrational spectroscopy, powder X-ray diffraction data, thermogravimetry, differential scanning calorimetry, and DFT calculations.

Synthesis and Characterization of the First Tin Fluoride Borate Sn3 [B3 O7 ]F with Second Harmonic Generation Response.

The new non-centrosymmetric tin fluoride borate Sn3 [B3 O7 ]F was synthesized hydrothermally, and was characterized by single-crystal and powder X-ray diffraction, vibrational spectroscopy, DFT calculations, second harmonic generation (SHG) measurements, thermogravimetry, and differential scanning calorimetry. Its SHG response is about 12 times that of quartz. The compound crystallizes in the non-centrosymmetric orthorhombic space group Pna21 with lattice parameters a=922.4(2), b=769.8(4), and c=1221.9(6) pm (Z=4). Characteristic for the structure are isolated B3 O7 moieties, consisting of two corner-sharing BO3 units and one BO4 tetrahedron. These occupy half of the octahedral voids of a slightly distorted hexagonal closest packing of Sn2+ atoms, with [SnF]+ units in the other half of the octahedral voids. Sn3 [B3 O7 ]F is transparent over a wide spectral range with a UV cut-off edge at about 263 nm.

In vitro characterization of insulin containing thiomeric microparticles as nasal drug delivery system.

This study focused on a novel two step preparation method for the generation of insulin containing thiomer microparticles. The first step utilized the interpolymer complexation between poly(vinyl pyrrolidone) (PVP) and poly(acrylic acid) (PAA) or poly(acrylic acid)-cysteine (PAA-Cys), respectively, in the presence of insulin. Thereafter lyophilized coprecipitates were micronized via air jet mill. Particles were evaluated regarding size, morphology, insulin release and the effect on ciliary beat frequency of human nasal epithelial cells in vitro. Results displayed mean particle sizes of 2.6±1.6µm and 2.8±1.7µm for PAA/PVP/insulin and PAA-Cys/PVP/insulin microparticles, respectively, in a range where volitional impaction of particles on nasal epithelium takes place. Multi unit dosage forms showed in addition release for the incorporated insulin and nasal safety as to results of ciliary beat frequency studies (CBF). The introduced jet milled microparticles might in conclusion display a safe nasal insulin drug delivery system leading to improved absorption.