No abstract

29Si {1H} cross-polarization (CP) magic-angle spinning (MAS) nuclear nagnetic resonance (NMR) is shown to be a valuable tool for detection and quantification of thaumasite in cementitious systems. A 29Si {1H} CPIMAS NMR method for quantitative analysis of thaumasite employing 1H and 29Si rotating-frame relaxation times TH1p and TSi1p and the 1H—29Si CP time TSiH is introduced. The method is illustrated by determination of the thaumasite content in five laboratory samples containing carbonates and sulphates from different sources. The use of 29Si{lH} CP/MAS rather than 29Si MAS NMR for the detection of thaumasite is shown to reduce the instrument time by up to a factor of IOOO because of the large difference in 1H and 29 spin-lattice relaxation times (TH1 and TSi1) and the 29Si intensity gain by CP for this mineral. The non-standard behaviour of the 1H and 29 spin-lattice relaxation processes observed for some samples is shown to follow a decay exponential in t with time t. 27Al MAS NMR is used to quantify ettringite for some of the samples. In contrast to previous proposals on the mechanism for the formation of thaumasite, it is demonstrated using 29Si{lH} CP/MAS and 27Al MAS NMR that considerable quantities of thaumasite can be produced in virtually aluminium-free materials. 13C {lH} CP/MAS NMR of pure thaumasite shows its potential in characterizing the carbonate anions in this mineral.

The properties of cement-based binders change dramatically when ultrafine particles are homogeneously placed in the spaces between densely packed cement grains, the increased density and the refinement of the pore structure of such binders result in considerable increases in properties such as compressive strength, impermeability and adherence to fibres and aggregates. It has been shown that such cement-based binders may be processed by simple techniques, and that the resulting materials may replace metals, ceramics and plastics.

Five cases of primary malignant lymphomas of the salivary glands are reported. Four lymphomas arose in the parotid gland and one in the submandibular gland. All were non-Hodgkin lymphomas. In 4 cases the lymphomas were of low-grade malignancy, viz. 2 immunocytomas and 2 centroblastic/centrocytic malignant lymphomas, and 1 was a T-immunoblastic malignant lymphoma of high-grade malignancy. Four patients with localized disease were treated with radiotherapy and 1 patient with disseminated disease was treated with chemotherapy. One patient died from a disease unrelated to the malignant lymphoma, and 4 patients were alive at 66-136 months after treatment.

Chondrosarcoma of the larynx is a rare neoplasm. The characteristic features of this tumor are described, and a case in a 69-year-old woman is reported. This case demonstrates the difficulties of histological classification. On the first biopsy specimen a benign chondroma was diagnosed. However, the microscopical features of the excised tumor were those of a chondrosarcoma. It is generally accepted that radiotherapy is of no value; surgical treatment by laryngectomy is advised. Some authors recommend a conservative attitude towards these tumors, which are of low malignancy, the growth slow and the risk of local or distant metastases slight.