[Alumina reinforced porcelain jacket crown].
Aluminum oxides provide one of the most useful sources of high-strength and high-modulus crystals. New types of high alumina content glasses may replace feldspathic porcelains. Esthetics compare favorably.
Research in dental practice: a 'SWOT' analysis.
Most dental treatment, in most countries, is carried out in general dental practice. There is therefore a potential wealth of research material, although clinical evaluations have generally been carried out on hospital-based patients. Many types of research, such as clinical evaluations and assessments of new materials, may be appropriate to dental practice. Principal problems are that dental practices are established to treat patients efficiently and to provide an income for the staff of the practice. Time spent on research therefore cannot be used for patient treatment, so there are cost implications. Critics of practice-based research have commented on the lack of calibration of operative diagnoses and other variables; however, this variability is the stuff of dental practice, the real-world situation. Many of the difficulties in carrying out research in dental practice may be overcome. For the enlightened, it may be possible to turn observations based on the volume of treatment carried out in practice into robust, clinically related and relevant research projects based in the real world of dental practice.
l-Phenylalanine dehydrogenase from Brevibacterium sp. for production of l-phenylalanine by reductive amination of phenylpyruvate
SummaryFor production of l-phenylalanine the reductive amination of phenylpyruvate, catalyzed by phenylalanine-dehydrogenase was examined. To reach high levels and a sufficient stability of the inducible intracellular enzyme, growth conditions of Brevibacterium sp. are optimized. For continuous production of l-phenylalanine in an enzyme membrane reactor, the kinetic parameters of the partially purified enzyme are determined.In continuous production a space time yield of 37.4 g l-Phe l-1 d-1 can be reached.By means of the measured kinetic parameters and simultaneous calculation of the mass balances of all reaction components the behaviour of the reactor can be simulated. For certain conditions the multi-enzyme-system shows multiple steady-states.