Microwave-Hydrothermal Processing of BiFeO3 and CsAl2PO6

Microwave-hydrothermal (M-H) processing was compared with conventional-hydrothermal (C-H) processing in the crystallization of BiFeO₃ and CsAl₂PO₆ phases. The presence of the microwave field led to accelerated kinetics of the crystallization of both these phases as detected by powder X-ray diffraction. The acceleration of reaction rates under microwave field is expected to lead to energy savings during ceramic processing.     

Mutant K-ras oncogenes in colon cancers Do not predict Patient's chemotherapy response or survival

One half of human colon cancers bear mutant c-K-ras oncogenes. Mutant K-ras oncogenes are associated with shortened survival in non-small cell lung cancers, and, in cell line models, with resistance to cis-platinum and to ionizing radiation. This study examines whether mutant K-ras alleles in colon cancer alter patients' response to chemotherapy or survival. We studied 37 patients who received chemotherapy with 5-fluorouracil and leucovorin, Exon 1 of the c-K-ras gene was PCR amplified from DNA extracted from paraffin-embedded tumor blocks. The presence of mutant or wild-type c-K-ras alleles was determined by dideoxy sequencing of the PCR-amplified c-K-ras DNA. c-K-ras mutations at codons 12 or 13 were present in 19 and absent in 18 cases. Responses to chemotherapy were equally likely in patients with either wild-type or mutant c-K-ras, occurring in 28% of patients with wild-type ras and 32% of patients with mutant ras (P = 0.8). Survival was also indistinguishable among both groups. Median survival from diagnosis was 35 months for ras wild-type patients and 31 months for ras mutant patients (P = 0.96). Median survival from starting chemotherapy was 14 months for ras wild-type patients and 17 months for ras mutant patients (P = 0.26). Patients with colon cancers bearing either wild-type or mutant c-K-ras alleles are indistinguishable in overall survival and are equally likely to respond to 5-fluorouracil-based chemotherapy.     

Epitaxial Crystallization of Seeded Albite Glass

Glasses that are extremely difficult to crystallize are generally avoided in making glass-ceramics. It is now possible to crystallize such glasses epitaxially using isostructural seeds. The role of solid-state epitaxy in the crystallization of such albite (NaAlSi₃O₈) glass to glass-ceramic was investigated. The glass was seeded with extremely fine ZrO₂ (nonisostructural) and albite (isostructural) seed crystals. X-ray diffraction results indicated that the albite-seeded glass, heat-treated at 1000°C for 100 h, epitaxially crystallized to albite, while the ZrO₂ and unseeded glasses did not crystallize in identical heat-treatment conditions. In addition, the albite-seeded glass, heat-treated at 905°C for 10 d, crystallized mostly to albite, whereas the ZrO₂ and unseeded glasses at the same conditions contained only a small amount (<5 wt%) of nepheline (NaAlSiO₄). The microstructure of the epitaxially grown glass-ceramics showed that extremely fine crystals (∼0.2 μm thickness) were formed around the seed.     

Laser-Induced Calcite—Aragonite Transition

High-pressure phases of CaCO₃, namely aragonite, calcite II, and possibly calcite III, were synthesized in air by exposing 10- to 20-μm-size particles of CaCO₃ (calcite I phase) to a CO₂ laser radiation at short pulse lengths (≤0.1 ms). The process, therefore, has the same effect as exposing the particles to at least several hundred megapascals pressure. Processing at higher pulse lengths resulted in the decomposition of CaCO₃ to CaO and CO₂. The extent of decomposition increased with increasing pulse length.     

Diphasic ceramic composites via a sol-gel method

A sol-gel process is described for the preparation of diphasic composite materials. The method involves the growth of extremely fine crystalline or non-crystalline materials inside a pre-made gel structure (of SiO₂) by soaking the gel in metal nitrate solution and subsequent precipitation of the metal with the selected anions (using mineral acids) followed by a densification step.     

Effect of oxygen on structural properties of quenched Ge-Te melts

By the deliberate addition of oxygen (up to 1.0 at. % in the form of GeO₂), its effect on the structure and properties of quenched Ge-Te glasses was studied. The glass-forming region of the water-quenched melts is narrowed by the addition of oxygen impurity. Replica electron micrographs of the glasses show apparent coarsening of the microstructure by such an oxygen addition, whereas the crystallization behaviour of the splat-cooled melts studied by DTA did not change significantly with this oxygen addition. Morphological features of GeTe crystallites in the glass + crystal portion observed in the oxygen-containing melts are described. However, in cases when either the melts were splat-cooled in an oxidizing atmosphere, or the DTA runs were made in air, a two-stage crystallization reaction was observed on DTA thermograms. Reactivity of the melts with SiO₂ glass vials is enhanced by the existence of the impurity oxygen.