Erbium:YAG (2.94 mum) laser effects on dental tissues

Past trials with soft and calcified tissues have demonstrated that long pulse train (2.5 mus) Er:YAG (2.94 mum) laser may be used to ablate tooth structure of human teeth. Determination of physical and thermal damage to surrounding tissue during removal of enamel and dentin is a primary objective of this study. Extracted human teeth with thermal probes imbedded in the pulp chambers were submitted to cavity preparation using an Erbium YAG laser with water mist. Wavelength selection as well as use of a water mist during the procedure resulted in efficient tissue removal without significant surrounding damage. Ground sections and SEM sections of teeth showed little or no melting or ash formation in adjacent dentin and enamel and no visible change in the pulp chamber. The surfaces produced by laser ablation were rough and irregular with craters and grooves. Average temperature change in the pulp chamber monitored during tooth preparation was 2.2 degrees Centigrade. These findings suggest that constantly available water aids vaporization and microexplosions, increasing the efficiency of tooth structure removal, and aids in cooling of the tooth structures. The long pulse Er:YAG (2.94 mum) laser may be an effective method for tooth reduction applications when used with a water mist.     

Preparation and polymerization of some N-(dialkylaminoalkyl)acrylamides

A series of N-(dialkylaminoalkyl)acrylamides was synthesized by reductive amination of N-(1,1-dimethyl-3-oxobutyl)acrylamide (diacetone acrylamide) and by the reaction of either an alkenylamine or an amino alcohol with acrylonitrile. These monomers homopolymerize and copolymerize readily to form high molecular weight products. The solubility of the monomers and their homopolymers in water ranges from soluble to insoluble at room temperature. The insoluble materials can be quaternized readily to produce water-soluble products. The solubility of the homopolymers in water decreases with increasing temperature. Glass transition and decomposition temperatures of the homopolymers are reported.     

Contribution to the quantitative x-ray analysis of individual submicrometre particles: Asbestos fibres

Summary A procedure for the analysis of individual asbestos fibres in the submicrometre diameter range, based on the ratio method of thin film analysis, is presented. The reliability of this method has been tested in a study of identification of asbestos fibres. The systematic and statistical errors were investigated.

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Beitrag zur quantitativen Röntgenmikroanalyse einzelner Submikrometerteilchen: Asbestfasern

Zusammenfassung Es wurde versucht, eine Quantifizierungsmethode analog der Verhältnismethode zur Analyse dünner Schichten für die Analyse von Asbestfasern mit Durchmessern im Submikrometerbereich zu entwickeln. Die Zuverlässigkeit der Methode wurde mit einem Anwendungsbeispiel überprüft, und alle systematischen und statistischen Fehler wurden dargelegt.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Liquid chromatographic determination of sulindac and metabolites in serum

An improved liquid chromatographic procedure is described for the quantitative determination of sulindac, sulindac sulfone, and sulindac sulfide from serum. The procedure makes use of acetonitrile extraction of the compounds of interest from acidified serum samples. Under these conditions extraction efficiencies in the 85 percent range are obtained for each of the compounds. The liquid chromatographic separation of the compounds of interest and the internal standard (indomethacin) is accomplished in an isocratic elution procedure using a nitrile (CN) stationary phase. The HPLC separation procedure is completed in less than 10 minutes, giving excellent resolution and peak shape.     

ON THE CONVERGENCE OF THE PARABOLIC APPROXIMATION OF A CONSERVATION LAW IN SEVERAL SPACE DIMENSIONS

1.IntrodnctionWegiveaproofofthestrongconvergenceinofthesolutionoftheparabolicapproximationtowardstheentropicsolutiontothescalarconservationlawwhereuo(RN),udenotessomeapproximationofuosuchthatandthefluxfsatisfiesTheconvergenceoftheapproximatesolutions...     

Differential inhibition of postnatal brain,spinal cord and body growth by a growth hormone antagonist

Background  

Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH.     

Methane–oxygen detonation characteristics at elevated pre-detonation pressures

The detonation characteristics of methane–oxygen mixtures at pre-detonation pressures of 101–1,013 kPa were investigated in a detonation tube. Both pure methane–oxygen mixtures and mixtures with argon dilution were explored. Measurements made include cell sizes via soot foil, wave speed via high speed ion probes / pressure transducers, and temperature / H₂O molar concentration profiles via 100 kHz absorption spectroscopy. Measured cell widths agreed with predicted cell widths based on a ZND length correlation. In addition, the power law fit of cell width with pre-detonation pressure agreed with previous data at less than 101 kPa. Measured detonation wave speeds agreed within 3% of Chapmen-Jouguet for all cases. H₂O molar density and temperature were successfully captured up to 507 kPa. However, above 507 kPa pre-detonation pressure, low signal to noise ratio and poor spectral fits at the extreme conditions of the von Neumann spike resulted in unacceptable uncertainty. These results provide a unique dataset to validate kinetics models and high-fidelity computation fluid dynamics codes for methane-oxygen detonations at elevated pre-detonation pressures relevant to rotating detonation rocket engines.     

C-terminal processing of yeast Spt7 occurs in the absence of functional SAGA complex

Background  

Spt7 is an integral component of the multi-subunit SAGA complex that is required for the expression of ~10% of yeast genes. Two forms of Spt7 have been identified, the second of which is truncated at its C-terminus and found in the SAGA-like (SLIK) complex.     

Investigation of the structure of detonation waves in a non-premixed hydrogen–air rotating detonation engine using mid-infrared imaging

The structure of detonation waves propagating through the annular channel of an optically accessible non-premixed rotating detonation engine (RDE) are investigated using mid-infrared imaging. The RDE is operated on hydrogen–air mixtures for a range of air mass flow rates and equivalence ratios. Instantaneous images of the radiation intensity from water vapor are acquired using a mid-infrared camera and a band-pass filter (2.890?±?0.033?µm). The instantaneous mid-infrared images reveal the stochastic nature of the detonation wave structure, position and angle of oblique and reflected shock waves, presence of shear layer separating products from the previous and current cycles, and extent of mixing between the reactants and products in the reactant fill zone in front of the detonation wave. The images show negligible signal directly in front of the detonation waves suggesting that there is minimal mixing between the reactants and products from the previous cycle ahead of the detonation wave for most operating conditions. The mid-infrared images provide insights useful for improving fundamental understanding of the detonation structure in RDEs and benchmark data for evaluating modeling and simulation results of RDEs.     

Solvent isotope effects on interfacial protein electron transfer in crystals and electrode films

D(2)O-grown crystals of yeast zinc porphyrin substituted cytochrome c peroxidase (ZnCcP) in complex with yeast iso-1-cytochrome c (yCc) diffract to higher resolution (1.7 A) and pack differently than H(2)O-grown crystals (2.4-3.0 A). Two ZnCcP's bind the same yCc (porphyrin-to-porphyrin separations of 19 and 29 A), with one ZnCcP interacting through the same interface found in the H(2)O crystals. The triplet excited-state of at least one of the two unique ZnCcP's is quenched by electron transfer (ET) to Fe(III)yCc (k(e) = 220 s(-1)). Measurement of thermal recombination ET between Fe(II)yCc and ZnCcP+ in the D(2)O-treated crystals has both slow and fast components that differ by 2 orders of magnitude (k(eb)(1) = 2200 s(-1), k(eb)(2) = 30 s(-1)). Back ET in H(2)O-grown crystals is too fast for observation, but soaking H(2)O-grown crystals in D(2)O for hours generates slower back ET, with kinetics similar to those of the D(2)O-grown crystals (k(eb)(1) = 7000 s(-1), k(eb)(2) = 100 s(-1)). Protein-film voltammetry of yCc adsorbed to mixed alkanethiol monolayers on gold electrodes shows slower ET for D(2)O-grown yCc films than for H(2)O-grown films (k(H) = 800 s(-1); k(D) = 540 s(-1) at 20 degrees C). Soaking H(2)O- or D(2)O-grown films in the counter solvent produces an immediate inverse isotope effect that diminishes over hours until the ET rate reaches that found in the counter solvent. Thus, D(2)O substitution perturbs interactions and ET between yCc and either CcP or electrode films. The effects derive from slow exchanging protons or solvent molecules that in the crystal produce only small structural changes.