Characterization and properties of novel gallium-doped calcium phosphate ceramics

Addition of a gallium (Ga) precursor in the typical reaction protocols used for the preparation of β-tricalcium phosphate (β-TCP) led to novel Ga-doped β-TCP ceramics with rhombohedral structures (R3c space group). From the refinement of their X-ray diffraction patterns, it was found that the incorporation of Ga in the β-TCP network occurs by substitution of one of the five calcium (Ca) sites, while occupation of another Ca site decreases in inverse proportion to the Ga content in the structure. The Ga local environment and the modification of the phosphorus environments due to the Ga/Ca substitution in Ga-doped β-TCP compounds are probed using (31)P and (71)Ga magic-angle spinning NMR. A decrease of the unit cell volume is observed with increasing Ga content, together with improved mechanical properties. Indeed, the compressive strength of these new bioceramics is enhanced in direct proportion of the Ga content, up to a 2.6-fold increase as compared to pure β-TCP.     

The world viewed from outside

Simple models of the cosmos are given by space-forms of a stretched 3-sphere. The isometric embedding of these manifolds into higher-dimensional Euclidean spaces is an unsolved problem that has yielded some partial solutions of bizarre beauty.     

Colachrom,a command language for chromatographic data processing

A command language for the interactive computer processing of chromatograms is described. Report data files, resulting from a peak evaluation program, are processed with single-line commands. Reference peaks for quantitative evaluation or for retention index calculations can be specified, compound names or response factors be assigned, etc. Customer-specific reports can be generated. Several commands operate on the unreduced digitized chromatograms, e.g., repeat peak evaluation with modified peak search parameters or with a user-corrected baseline. Commands can be combined into procedures for semi-automatic processing of series of chromatograms. Various forms of interactive graphical presentations supplement the command language.     

A centralized,hierarchically structured computer system for chemical research and analytical instrumentation

An hierarchically structured, centralized compute system, replacing an obsolete central DECsystem-10, can be used for all the computational tasks in chemical research, as well as for real-time data acquisition and evaluation for numerous analytical instruments, required in a large Institute. In this hierarchical system, the real-time tasks are done by local minicomputer satellites that are tailored to special requirements in the laboratories. All higher level data processing and data storage demands are covered by the central system, consisting of two VAX11/780 computers, to which all satellites as well as all user terminals are connected. The design criteria are described as well as some of the software packages developed for this system.