Mechanical characteristics of optical coatings prepared by various techniques: a comparative study

Good performance of optical coatings depends on the appropriate combination of optical and mechanical properties. Therefore, successful applications require good understanding of the relationship between optical microstructural and mechanical characteristics and film stability. In addition, there is a lack of standard mechanical tests that allow one to compare film properties measured in different laboratories. We give an overview of the methodology of mechanical measurements suitable for optical coatings; this includes depth-sensing indentation, scratch resistance, friction, abrasion and wear testing, and stress and adhesion evaluation. We used the techniques mentioned above in the same laboratory to systematically compare the mechanical behavior of frequently used high- and low-index materials, namely, TiO2, Ta2O5, and SiO2, prepared by different complementary techniques. They include ion-beam-assisted deposition by electron-beam evaporation, magnetron sputtering, dual-ion-beam sputtering, plasma-enhanced chemical-vapor deposition, and filtered cathodic arc deposition. The mechanical properties are correlated with the film microstructure that is inherently related to energetic conditions during film growth.     

The effect of treatment with clofibrate on hepatic triglyceride and lipoprotein lipase activities of post heparin plasma in male patients with hyperlipoproteinemia

Twelve male patients with hyperlipoproteinemia were treated with clofibrate, 1 g twice daily. Serum triglyceride concentration decreased on the average 28 +/- 6%. No significant change of serum cholesterol concentration occurred. Post heparin plasma lipoprotein lipase activity isolated and partially purified by heparin Sepharose affinity chromatography was determined quantitatively. During the clofibrate treatment this enzyme activity increased 48 +/- 9%. The post heparin hepatic triglyceride lipase did not change significantly. The possibility that the serum triglyceride-lowering effect of clofibrate might partly be explained by an increased removal rate of triglyceride rich lipoproteins through increased lipoprotein lipase activity is discussed.     

Monolayer-protected gold nanoparticles as a stationary phase for open tubular gas chromatography

The use of a thin film of monolayer-protected gold nanoparticles (MPNs) as a stationary phase for gas chromatography (GC) is reported. Deposition of a MPN film was obtained in a 2-m, 530-microm-i.d. deactivated silica capillary using gravity to force the solution containing the MPN material through the capillary. By SEM analysis, the average film thickness was determined to be 60.7 nm. The retention behavior for the dodecanethiol MPN column was studied using four compound classes (alkanes, alcohols, aromatics, ketones), and retention orders were objectively compared to a commercially available column (AT-1, 100-nm film thickness). Separation of an eight-component mixture was performed using both isothermal and temperature-programming methods with the dodecanethiol MPN phase and compared to an isothermal separation with the AT-1 phase. The AT-1 phase separation had an efficiency, N, of 6200 (k' = 0.33) while the dodecanethiol MPN phase separation had an efficiency, N, of 5700 (k' = 0.21) for the same analyte, octane. The reduced plate height, h, for octane was found to be less than 1 at the optimum linear flow velocity, indicating the MPN column operated near the optimum possible performance level. Robustness of the MPN phase is also discussed with consistent performance observed over several months. Overall, MPNs appear promising as a stationary-phase material for GC and as an experimental platform to study their thermodynamic and mass-transfer properties.     

A method for quantification from composite spectra: application to the determination of isomeric DNA photoproducts by tandem mass spectrometry

Quantification of mixture components from their composite optical or mass spectra is a common need in analytical chemistry. We encountered the need when applying a combination of enzymatic digestion with nuclease P1 and tandem mass spectrometry to a mixture of isomeric photomodified oligodeoxynucleotides. In the procedure, we collisionally activated the [M - H]- or [M + Na - 2H]- ion of trinucleotide triphosphates, which were extricated enzymatically from the larger, damaged oligodeoxynucleotides, and we measured the relative abundances of characteristic fragment ions. The results sometimes yield curved calibrations for plots of the relative fragment ion abundances in the product ion spectra of isomers versus their relative amounts. We developed a normalized linear model, which brings understanding to the nonlinear plots and allows quantification of the mixture components from their composite spectra. The outcome demonstrates a general quantification procedure and shows that different yields for generating fragment ions from different constituents of the mixture cause the curved calibration lines.     

Matrix-assisted laser desorption/ionization mass spectrometry for locating abasic sites and determining the rates of enzymatic hydrolysis of model oligodeoxynucleotides

A method using a combination of exonuclease enzymatic digestion and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was developed to locate model abasic sites in a series of model 21-base oligodeoxynucleotides in which a nucleobase was replaced by a hydrogen atom. The exonuclease digestion rate, with either snake venom phosphodiesterase (SVP) or bovine spleen phosphodiesterase (BSP), clearly slows as the digestion approaches the abasic sites and stops as it reaches it. An oligodeoxynucleotide containing an abasic site in which OH replaces the nucleobase shows similar results. MALDI mass spectra taken at appropriate times during the course of hydrolysis are the basis for rate measurements, and the kinetics also reveal the location of the abasic site. A mathematical treatment of the time-dependent MALDI data was implemented to obtain rate curves and rate constants for the enzymatic digestion of both modified and unmodified oligodeoxynucleotides.     

Harnessing the need for immediate gratification: Cognitive reconstrual modulates the reward value of temptations.

Many of us succumb to temptations, despite knowing that we will later regret doing so. How can such behavior be avoided? In three studies, the authors tested the hypothesis that reconstruing temptation as a test of a valued internal quality ("willpower") would decrease the tendency to succumb by reducing the appeal of the temptation. In Study 1, participants who construed a challenging handgrip task as a test of willpower resisted the temptation to terminate the painful task longer than participants who did not. In Study 2, participants performed a handgrip task twice. Only participants who changed their construal of the task into a test of willpower improved their performance. In Study 3, participants took a timed math test while being tempted by comedy clips. Participants who reconstrued the situation as willpower test compared with participants who did not, (a) enjoyed the videos less, and (b) were better able to resist the tempting videos. These studies demonstrate that cognitive reconstrual can be used to modify reward contingencies, so that succumbing to temptation becomes less appealing, and resisting temptation becomes more appealing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deformable dielectrics – optimization of heterogeneities

The modeling and the numerical simulation of deformable dielectrics are discussed in a coupled electro-mechanical framework. It is demonstrated how the Maxwell stress contributions can be implemented efficiently into a finite element method. By using numerical simulation, the electro-static contraction of a soft actuator is calculated and examined. The operational curve, i.e. the variation of the compression versus the applied electric field, is obtained for a capacitor-like setup using the neo-Hooke material model. Furthermore, the idea of introducing ceramic inclusions in the soft elastomer is discussed, which is shown to be capable of improving the efficiency of the actuator. By representative examples, the geometry optimization of the inclusion is considered.     

Photophobia and phonophobia in migraineurs between attacks

This study investigated whether migraineurs are more sensitive to light and sound while headache-free than are healthy people. Fifty-two migraineurs (mean age 39 years) were selected using the International Headache Society diagnostic criteria for migraine. Forty-eight healthy controls were matched for age, sex, and race (mean age 36 years). Visual and auditory discomfort thresholds were measured by exposing subjects to increasing light and sound until they complained of discomfort. There were significant differences between groups in both the light discomfort threshold (P < 0.00005) and the hearing discomfort threshold (P < 0.0005). The thresholds for both were lower in the migraineurs. Overall, for both groups together, there was a significant negative correlation between light discomfort threshold and age (correlation coefficient -0.2276, P = 0.011), but not for the hearing discomfort threshold and age (P = 0.275). The results show that the migraineurs were significantly more sensitive to light and sound when headache-free than were healthy controls. The apparent increased intolerance to light in both groups together noted with increased age, did not apply to the migraine group.     

Numerical Simulation of a Mixed-mode Dynamic Fracture Experiment

A time-domain boundary element method is applied to simulate mixed-mode dynamic fracture experiments performed on compact compression specimens (CCS) in a split Hopkinson bar. This numerical investigation addresses the time histories of the mode I and II stress intensity factors for the precracked CCS, the instant and angle of crack initiation as well as the resulting crack paths in dependence upon the external load. The aim of the study is two-fold: to gain deeper insight into the mixed-mode dynamic fracture process under investigation and to test the applicability of our recently developed numerical method. Numerical results are compared to experimental data reported in the literature. Furthermore, aspects of modelling the experimental set-up in the framework of the boundary element method are discussed, and advantages and shortcomings are analyzed. This revised version was published online in July 2006 with corrections to the Cover Date.