Luminescence-Based Spectroelectrochemical Sensor for [Tc(dmpe)(3)](2+/+) (dmpe = 1,2-bis(dimethylphosphino)ethane) within a Charge-Selective Polymer Film

A spectroelectrochemical sensor consisting of an indium tin oxide (ITO) optically transparent electrode (OTE) coated with a thin film of partially sulfonated polystyrene-blockpoly(ethylene-ran-butylene)-block-polystyrene (SSEBS) was developed for [Tc(dmpe)(3)](+) (dmpe = 1,2-bis(dimethylphosphino)ethane). [Tc(dmpe)(3)](+) was preconcentrated by ion-exchange into the SSEBS film after a 20 min exposure to aqueous [Tc(dmpe)(3)](+) solution, resulting in a 14-fold increase in cathodic peak current compared to a bare OTE. Colorless [Tc(dmpe)(3)](+) was reversibly oxidized to colored [Tc(dmpe)(3)](2+) by cyclic voltammetry. Detection of [Tc(dmpe)(3)](2+) was accomplished through emission spectroscopy by electrochemically oxidizing the complex from nonemissive [Tc(dmpe)(3)](+) to emissive [Tc(dmpe)(3)](2+). The working principle of the sensor consisted of electrochemically cycling between nonemissive [Tc(dmpe)(3)](+) and emissive [Tc(dmpe)(3)](2+) and monitoring the modulated emission (λ(exc) = 532 nm; λ(em) = 660 nm). The sensor gave a linear response over the concentration range of 0.16-340.0 μM of [Tc(dmpe)(3)](2+/+) in aqueous phase with a detection limit of 24 nM.     

Piezoelectric multilayer actuator life test

Potential NASA optical missions such as the Space Interferometer Mission require actuators for precision positioning to accuracies of the order of nanometers. Commercially available multilayer piezoelectric stack actuators are being considered for driving these precision mirror positioning mechanisms. These mechanisms have potential mission operational requirements that exceed 5 years for one mission life. To test the feasibility of using these commercial actuators for these applications and to determine their reliability and the redundancy requirements, a life test study was undertaken. The nominal actuator requirements for the most critical actuators on the Space Interferometry Mission (SIM) in terms of number of cycles was estimated from the Modulation Optics Mechanism (MOM) and Pathlength control Optics Mechanism (POM) and these requirements were used to define the study. At a nominal drive frequency of 250 Hz, one mission life is calculated to be 40 billion cycles. In this study, a set of commercial PZT stacks configured in a potential flight actuator configuration (pre-stressed to 18 MPa and bonded in flexures) were tested for up to 100 billion cycles. Each test flexure allowed for two sets of primary and redundant stacks to be mechanically connected in series. The tests were controlled using an automated software control and data acquisition system that set up the test parameters and monitored the waveform of the stack electrical current and voltage. The samples were driven between 0 and 20 V at 2000 Hz to accelerate the life test and mimic the voltage amplitude that is expected to be applied to the stacks during operation. During the life test, 10 primary stacks were driven and 10 redundant stacks, mechanically in series with the driven stacks, were open-circuited. The stroke determined from a strain gauge, the temperature and humidity in the chamber, and the temperature of each individual stack were recorded. Other properties of the stacks, including the displacement from a capacitance gap sensor and impedance spectra were measured at specific intervals. The average degradation in the stroke over the life test was found to be small (<3%) for the primary stacks and <4% for the redundant stacks. It was noted that about half of the stroke reduction occurred within the first 10 billion cycles. At the end of the life test, it was found that the actuator could recover about half of the lost stroke by applying a dc voltage of 100 V at room temperature. The data up to 100 billion cycles for these tests and the analysis of the experimental results are presented in this paper.     

A tissue-mimicking ultrasound test object using droplet vaporization to create point targets

Ultrasound test objects containing reference point targets could be useful for evaluating ultrasound systems and phase aberration correction methods. Polyacrylamide gels containing albumin-stabilized droplets (3.6 μm mean diameter) of dodecafluoropentane (DDFP) are being developed for this purpose. Perturbation by ultrasound causes spontaneous vaporization of the superheated droplets to form gas bubbles, a process termed acoustic droplet vaporization (ADV). The resulting bubbles (20 to 160 μmm diameter) are small compared with acoustic wavelengths in diagnostic ultrasound and are theoretically suitable for use as point targets (phase errors < 20° for typical f-numbers). Bubbles distributed throughout the material are convenient for determining the point spread function in an imaging plane or volume. Cooling the gel causes condensation of the DDFP droplets, which may be useful for storage. Studying ADV in such viscoelastic media could provide insight into potential bioeffects from rapid bubble formation.     

Raman spectroscopy using 1550 nm (retina-safe) laser excitation

During the past decade, the use of portable Raman analyzers for field measurements has grown dramatically. However, most analyzers use 785 nm excitation lasers that can cause permanent eye damage. To overcome this safety concern, we have built a portable Fourier transform (FT) Raman analyzer using a 1550 nm retina-safe excitation laser and have compared its performance to our 1064 nm FT-Raman analyzer, which uses the same optical design. Raman theory predicts approximately five times lower peak intensities at 1550 nm. Although we found that intensities were as much as 20 times less intense, the analyzer is still capable of measuring spectra of sufficient quality to identify and differentiate chemicals.     

Using R to compare least-squares fit models: When it must fail

R² can be used correctly to select from among competing least-squares fit models when the data are fitted in common form and with common weighting. However, when models are compared by fitting data that have been mathematically transformed in different ways, R² is a flawed statistic, even when the data are properly weighted in accord with the transformations. The reason is that in its most commonly used form, R²can be expressed in terms of the excess variance (s²) and the total variance in y (s_y²) — the first of which is either invariant or approximately so with proper weighting, but the second of which can vary substantially in data transformations. When given data are analyzed “as is” with different models and fixed weights, s_y² remains constant and R² is a valid statistic. However, then s², and χ² in weighted fitting, are arguably better metrics for such comparisons.     

New technologies for solar energy silicon: Cost analysis of BCL process

New technologies for producing polysilicon are being developed to provide lower cost material for solar cells which convert sunlight into electricity. This article presents results for the BCL Process (Battelle Columbus Laboratories), which produces the solar-cell silicon by reduction of silicon tetrachloride with zinc vapor. The UCC Silane Process (Union Carbide Corporation) was reported in a previous article.Cost, sensitivity and profitability analysis results are presented based on a preliminary process design of a plant to produce 1000 metric tons/year of silicon by the BCL Process. Profitability analysis indicates a sales price of 12.1–19.4$/kg of silicon (1980 dollars) at a 0–25 per cent DCF rate of return on investment after taxes. These results indicate good potential for meeting the goal of providing lower cost material for silicon solar cells.     

Zur Beziehung zwischen Fettgehalt und Wassergehalt bei ungewaschener Süßrahmbutter (Fritzbutter)

European Food Research and Technology - Bei der Auswertung der Untersuchungsergebnisse von 547 Proben ungewaschener Süßrahmbutter (Fritzbutter) ergab sich eine enge Beziehung zwischen...     

The effects of the DRD2 polymorphism on smoking cessation and negative affect: evidence for a pharmacogenetic effect on mood.

This study evaluated the relationship between smoking cessation treatment outcome and the DRD2 polymorphism. Participants were 134 smokers who took part in a larger clinical trial evaluating the effects of an antidepressant medication (venlafaxine or placebo) plus standard care (brief counseling and nicotine replacement therapy). Venlafaxine is an antidepressant that inhibits the reuptake of serotonin and norepinephrine. A1 smokers were expected to quit significantly less often on placebo, although the abstinence rates between A1s and A2s on active drug were not expected to differ (i.e., an interaction between genotype and drug was hypothesized). In addition, antidepressant therapy was expected to have a similar genotype x treatment interaction on negative affect reduction. The results showed that smokers carrying the DRD2 A1 allele (A1/A1/A2) quit significantly less often than the homozygous A2s (OR=1.54, 95% CI=1.01-2.36). No interaction with treatment was observed. A significant pharmacogenetic effect of the drug on negative mood while quitting also was noted. Smokers absent the A1 allele (A2/A2) responded to the drug with a substantial reduction in negative affect, whereas those with the A1 allele showed no significant reduction in negative mood, F(1, 130)=5.95, p=.01. These results are contrary to expectations and suggest that although A1s may have more difficulty quitting, adding venlafaxine does not improve abstinence or mood. However, the results for the A2s provide evidence for a genotype-specific response to a pharmacological intervention, which could have implications for the development of future treatments.