Building laminate veneers and fixed bridges with polymer glass technology

A new type of material is being introduced to American dentistry. The material is a polymer glass, tested in Europe as Artglass. The material is purported to be equal to or better than porcelain for esthetic dentistry. The strength, color translucency, and color vitality allow minimal destruction of enamel for esthetics. An Artglass occlusal is less abrasive to enamel than porcelain and approximates gold. The characteristics of this material system introduces "minimal invasive dentistry" to routine dental repair and reconstruction. A case study of the senior author's reconstruction of his anterior teeth is presented.     

Effect of antacid on bioavailability of a sustained-release theophylline preparation

The effect of coadministration of an antacid on bioavailability of a sustained-release theophylline tablet preparation (Theo-Dur) was studied by crossover comparison in five young, healthy, nonsmoking volunteers. Water 90 ml, or "high potency" aluminum-magnesium hydroxide antacid (Mylanta II) 10 ml and water 80 ml were administered concurrently with sustained-release theophylline 600 mg. Eleven blood samples were collected over the next 24 hours. Serum was analyzed with high pressure liquid chromatography technique to determine theophylline concentration. Peak serum concentration (Cmax) and time to peak concentration (tmax) were determined, and area under the 24-hour serum concentration-time curve (AUC) was calculated by the trapezoidal rule for each subject at each study interval. The Student's paired t-test was used to compare Cmax, tmax, and AUC for both treatments. A uniform difference was found between groups in Cmax. Cmax was higher in subjects when treated with the antacid (10.45 +/- 3.03 vs. 8.30 +/- 2.90 micrograms/ml, p less than 0.05) than when given theophylline alone. The mean tmax for the two treatments did not differ (10.4 +/- 1.67 h-combination vs. 10.8 +/- 1.1 h-theophylline, p greater than 0.05). Likewise, mean AUC was unchanged by the coadministration of antacid (140.65 +/- 41.6 micrograms/ml.h--combination vs. 155.13 +/- 46.6 micrograms/h--theophylline, p greater than 0.05). The use of a high-potency antacid product did not decrease the extent of theophylline absorption from this sustained-release product, but did increase Cmax and, presumably, rate of absorption. High-potency aluminum-magnesium antacids can probably be used in combination with this sustained-release theophylline tablet without detriment to therapy.     

Changes in pheromone titer of oblique-banded leafroller,Choristoneura rosaceana,virgin females as a function of time of day,age, and temperature

Under a 16:8 hr light-dark photoperiod and 20C constant temperature, the titers of (Z)-11-tetradecenyl acetate (Z11–14:Ac), (E)-11-tetradecenyl acetate (E11–14:Ac) and (Z)-11-tetradecenol (Z11–14:OH) produced by different-agedChoristoneura rosaceana virgin females varied significantly during the scotophase, with the maximum titer occurring before the onset of calling in day-0 and day-3 females, while in day-5 females the titer remained constant throughout the calling period. There was a significant decrease in the titer of all pheromone components with age, explaining the lesser attractiveness of day-5 females relative to day-0 and day-3 females observed in the field. Under a cold thermocycle simulating condition during the second flight period in the fall, the titers of all pheromone components did not vary with time of day. There was a significant decrease in the amount ofZ11–14:Ac with age but no changes occurred in the minor components. Furthermore, for any given age tested, the amount of each component produced during the period of maximal calling activity remained relatively similar at the two temperature regimes. However, as with the expression of calling behavior, pheromone production was initiated earlier at cooler than at warmer temperatures. At both temperature regimes, female age and time of day influenced the ratio of each pheromone component. These results are discussed in relation to the hypothesis that by calling earlier, less attractive older females may increase their probability of mating.     

Oral-contraceptive-induced hypertension after adrenalectomy and hypophysectomy

The cause of oral-contraceptive-induced hypertension in certain susceptible subjects is obscure. We describe a woman who was receiving replacement doses of fludrocortisone acetate after adrenalectomy and hypophysectomy who developed high blood pressure while ingesting an estrogen-containing oral contraceptive. Renin substrate level was increased, but renin activity was suppressed and unresponsive to tilting. The patient developed a markedly exaggerated natriuresis when infused with saline. Both blood pressure and her responses to infused sodium and tilting normalized after discontinuance of the oral contraceptive medication. In this adrenalectomized patient, the estrogenic component of the pill acting synergistically with a fixed ("nonsuppressible") replacement dose of mineralocorticoid seems to have caused a volume-related hypertension.     

Growth of conformal single-walled carbon nanotube films from Mo/Fe/Al2O3 deposited by electron beam evaporation

We discuss growth of high-quality carbon nanotube (CNT) films on bare and microstructured silicon substrates by atmospheric pressure thermal chemical vapor deposition (CVD), from a Mo/Fe/Al₂O₃ catalyst film deposited by entirely electron beam evaporation. High-density films having a tangled morphology and a Raman G/D ratio of at least 20 are grown over a temperature range of 750-900 °C. H₂ is necessary for CNT growth from this catalyst in a CH₄ environment, and at 875 °C the highest yield is obtained from a mixture of 10%/90% H₂/CH₄. We demonstrate for the first time that physical deposition of the catalyst film enables growth of uniform and conformal CNT films on a variety of silicon microstructures, including vertical sidewalls fabricated by reactive ion etching and angled surfaces fabricated by anisotropic wet etching. Our results confirm that adding Mo to Fe promotes high-yield SWNT growth in H₂/CH₄; however, Mo/Fe/Al₂O₃ gives poor-quality multi-walled CNTs (MWNTs) in H₂/C₂H₄. An exceptional yield of vertically-aligned MWNTs grows from only Fe/Al₂O₃ in H₂/C₂H₄. These results emphasize the synergy between the catalyst and gas activity in determining the morphology, yield, and quality of CNTs grown by CVD, and enable direct growth of CNT films in micromachined systems for a variety of applications.     

Hourly simulations of the microwave brightness temperature of seasonal snow in Quebec, Canada, using a coupled snow evolution-emission model

To interpret the snowpack evolution, and in particular to estimate snow water equivalent (SWE), passive microwave remote sensing has proved to be a useful tool given its sensitivity to snow properties. However, the main uncertainties using existing SWE algorithms arise from snow metamorphism which evolves during the winter season, and changes the snow emissivity. To consider the evolution in snow emissivity a coupled snow evolution-emission model can be used to simulate the brightness temperature (T_B) of the snowpack.During a dedicated campaign in the winter season, from November to April, of 2007-2008 two surface-based radiometers operating at 19 GHz and 37 GHz continuously measured the passive microwave radiation emitted through a seasonal snowpack in southern Quebec (Canada). This paper aims at modeling and interpreting this time series of T_B over the whole season, with an hourly step, using a coupled multi-layer snow evolution-emission model. The thermodynamic snow evolution model, referred as to Crocus, was driven by local meteorological measurements. Results from this model provided, in turn, the input variables to run the Microwave Emission Model of Layered Snowpacks (MEMLS) in order to predict T_B at 19 GHz and 37 GHz for both vertical (V) and horizontal (H) polarizations. The accuracy of T_B predicted by the Crocus-MEMLS coupled model was evaluated using continuous measurements from the surface-based radiometers.The weather conditions observed during the winter season were diverse, including several warm periods with melting snow and rain-on-snow events, producing very complex variations in the time series of T_B. To aid our analysis, we identified days with melting snow versus days with dry snow. The Crocus-MEMLS coupled model was able to accurately predict melt events with a success rate of 86%. The residual error was due to an overestimation of the duration of several melt events simulated by Crocus. This problem was explained by 1) a limitation of percolation, and 2) a very long-acting melt of lower layers due to geothermal flux.When the snowpack was completely dry, the global trend of T_B during the season was characterized by a decrease of T_B due to growth in the snow grain size. During most of the season, Crocus-MEMLS correctly predicted the evolution of T_B resulting from temperature gradient metamorphism; the root mean square errors ranged between 2.8 K for the 19 GHz vertical polarization (19V) and 6.9 K for the 37 GHz horizontal polarization (37H). However, during dry periods near the end of the season, the values of T_B were strongly overestimated. This overestimation was mainly due to a limitation of the growth of large snow grains in the wet snowpack simulated by Crocus. This effect was confirmed by estimating snow grain sizes from the observed T_B and the coupled model. The estimated snow grain sizes were larger and more realistic than those initially predicted by the Crocus model.     

Nano-patterning photosensitive polymers using local field enhancement at the end of apertureless SNOM tips

We show experimentally that local optical field enhancement can occur at the end of an apertureless SNOM tip illuminated by an external light source. Our approach consists in the use of a photosensitive polymer, placed in the tip near‐field, to record intensity distribution in the vicinity of the tip end. The excited nanometre‐size light source permits us to produce nano‐patterns on the polymer surface which are then characterized by atomic force microscopy. Experimental images show the influence, on the field enhancement, of three important experimental parameters: the polarization state of the incident light, the geometry of the external illumination and the radius of curvature of the tip apex. These results are shown to be in good agreement with two‐dimensional numerical calculations based on the finite‐difference time‐domain method. We show preliminary nanometre‐size patterns created by this nano‐source excited at a metallic tip extremity and discuss the potential of this approach for near‐field optical lithography.     

Activation and adherence of lyophilized human platelets on canine vessel strips in the Baumgartner perfusion chamber

The Baumgartner perfusion technique was used to test the ability of rehydrated lyophilized human platelets to adhere to the thrombogenic surface of a denuded arterial vessel segment and to undergo platelet activation under conditions of high shear. Twenty preparations of washed platelets were stabilized by 1-hour or 2-hour exposure to paraformaldehyde before freeze-drying in a Virtis 600 lyophilizer. The response of these fixed-dried preparations was compared with that of non-fixed platelets in fresh citrated whole blood. The outcome of each perfusion experiment was quantified in photomicrographs by morphometric estimation of the percent area of the vessel segment covered by adherent platelets after immunofluorescent staining with monoclonal antibodies to glycoprotein Ib (CD42) or glycoprotein IIbIIIa (CD41a). Evidence of activation in nonadherent platelets was examined by flow cytometry for CD62 and GP53 expression. In addition, thromboxane B2 was measured by radioimmunoassay as an index of platelet responsiveness to activation conditions during perfusion. The percent vessel coverage observed with lyophilized platelets in recombined whole blood was somewhat less than that of platelets in fresh whole blood (39% vs 73%, respectively). In other perfusion experiments performed with non-denuded vessel segments, the percent coverage was reduced by half or more for both types of platelet preparation. Scanning electron microscopy confirmed that the lyophilized platelets did not adhere to areas of intact endothelium. Furthermore, the lyophilized platelets showed a small-but-significant rise in CD62 or CD63 activation antigen expression and generated thromboxane B2 at about one third the rate of fresh platelets in these perfusion experiments. The thromboxane generation during perfusion was inhibited in fresh or lyophilized platelet preparations by pretreatment with indomethacin or PGE-1. We interpret these data as evidence of the ability of our lyophiilized platelet preparations to respond at least partially to physiologic stimuli and to adhere to appropriate thrombogenic sites to support hemostasis.