Delay discounting in current and former marijuana-dependent individuals.

Studies have found that a variety of drug-dependent groups discount delayed rewards more than matched controls. This study compared delay discounting for a hypothetical $1,000 reward among dependent marijuana users, former dependent marijuana users, and matched controls. Discounting of marijuana was also assessed in the currently marijuana-dependent group. No significant differences in discounting were detected among the groups; however, currently dependent users showed a trend to discount money more than the other 2 groups. Within the dependent marijuana group, marijuana was discounted more than money, and discounting for money and marijuana was significantly and positively correlated. Regression analyses indicated that delay discounting was more closely associated with tobacco use than marijuana use. A variety of questionnaires were also administered, including impulsivity questionnaires. Dependent marijuana users scored as significantly more impulsive on the Impulsiveness subscale of the Eysenck Impulsiveness–Venturesomeness–Empathy questionnaire than controls. However, the 3 groups did not significantly differ on several other personality questionnaires, including the Barratt Impulsivity Scale—11. The Stanford Time Perception Inventory Present–Fatalistic subscale was positively correlated with money and marijuana discounting, indicating that a greater sense of powerlessness over the future is related to greater delay discounting. Results suggest that current marijuana dependence may be associated with a trend toward increased delay discounting, but this effect size appears to be smaller for marijuana than for previously examined drugs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Etched quantum dots for all-optical and electro-optical switches

We present progress to date in the production of quantum dots etched from multiple quantum well structures for use in all-optical and electro-optical switches. Details of fabrication and comparisons to self-assembled quantum dot materials are described, and the direction of our continuing research is outlined.     

Heroin addicts have higher discount rates for delayed rewards than non-drug-using controls.

Fifty-six heroin addicts and 60 age-matched controls were offered choices between monetary rewards ($11–$80) available immediately and larger rewards ($25–$85) available after delays ranging from 1 week to 6 months. Participants had a 1-in-6 chance of winning a reward that they chose on one randomly selected trial. Delay-discounting rates were estimated from the pattern of participants' choices. The discounting model of impulsiveness (G. Ainslie, 1975) implies that delay-discounting rates are positively correlated with impulsiveness. On average, heroin addicts' discount rates were twice those of controls (p?=?.004), and discount rates were positively correlated with impulsivity as measured by self-report questionnaires (p?     

Delay discounting in current and never-before cigarette smokers: Similarities and differences across commodity, sign, and magnitude.

Research has found that nicotine-dependent individuals delay discount monetary gains at a higher rate than matched controls. Delay discount rates, however, have also been found to vary across within-subject variables such as the magnitude of the outcome (e.g., $10 or $1,000), whether the outcome constitutes a gain or a loss, and the commodity being evaluated (e.g., money or health). The present study comprehensively investigated the differences in delay discounting between current and never-before cigarette smokers and across these within-subject variables. Both groups exhibited a magnitude, sign, and commodity effect. Current smokers' delay discount rates for monetary outcomes, however, were higher than never-before smokers across all magnitudes and both signs. This trend was also found for delayed health outcomes, but failed to reach significance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A stochastic approach to calculate the particle size distribution function of soot particles in laminar premixed flames

We introduce an efficient stochastic approach to solve the population balance equation that describes the formation and oxidation of soot particles in a laminar premixed flame. The approach is based on a stochastic particle system representing the ensemble of soot particles. The processes contributing to the formation and oxidation of soot particles are treated in a probabilistic manner. The stochastic algorithm, which makes use of an efficient majorant kernel and the method of fictitious jumps, resolves the entire soot particle distribution (PSDF) without introducing additional closure assumptions. A fuel-rich laminar premixed acetylene flame is computed using a detailed kinetic soot model. Solutions are obtained for both, the stochastic approach and the method of moments combined with a modified version of the Premix, CHEMKIN code. In this manner, the accuracy of the method of moments in a laminar premixed flame simulation is investigated. It is found that the accuracy for the first moment is excellent (5% error), and mean error for rest of the moments is within 25%. Also the effect of the oxidation of the smallest particles (burnout) has been quantified but was found not to be important in the flame investigated. The time evolution of computed size distributions and their integral properties are compared to experimental measurements and the agreement was found to be satisfactory. Finally, the efficiency of the stochastic method is studied.     

Nicotine withdrawal versus other drug withdrawal syndromes: similarities and dissimilarities

Many of the symptoms of nicotine withdrawal are similar to those of other drug withdrawal syndromes: anxiety, awakening during sleep, depression, difficulty concentrating, impatience, irritability/anger and restlessness. Slowing of the heart rate and weight gain are distinguishing features of tobacco withdrawal. Although nicotine withdrawal may not produce medical consequences, it lasts for several weeks and can be severe in some smokers. Like most other drug withdrawals, nicotine withdrawal is time-limited, occurs in non-humans, is influenced by instructions/expectancy and abates with replacement therapy and gradual reduction. Unlike some other drug withdrawal syndromes, protracted, neonatal or precipitated withdrawal does not occur. Whether nicotine withdrawal is associated with tolerance, acute physical dependence, greater duration and intensity of use, rapid reinstatement, symptom stages, cross-dependence with other nicotine ligands, reduction by non-pharmacological interventions and genetic influences is unclear. Whether nicotine withdrawal plays a major role in relapse to smoking has not been established but this is also true for other drug withdrawal syndromes.     

Pseudospark switches for high repetition rates and high currentapplications

The state-of-the-art of pseudospark switch (PSS) development is reported. In addition to the replacement of thyratrons for high power applications in TE-gas-discharge lasers, PSSs have been tested at high repetition rates up to 2 kHz. In order to minimize the erosion rate and to reduce total switch inductance, multichannel PSSs with various geometrical configurations have been investigated: linear, coaxial, and radial arrangements of the parallel discharge channels. All three configurations possess distinct advantages in pulsed power technology, i.e. linear systems fit well into striplines. Beyond this, PSSs gain increasing importance in high current devices like fast pinches, plasma foci, or powerful modulators, i.e. for magnetoforming. A single-channel switch for hold-off voltages up to 30 kV at peak currents of ≈100 kA has been tested for a damped sinusoidal pulse of a 5 μs duration at a repetition rate of up to 0.2 Hz, with and without electrode cooling     

Coupled 3D master equation and 1D drift‐diffusion approach for advanced OLED modeling

A novel simulation approach for excitonic organic light‐emitting diodes (OLEDs) is established by combining a continuous one‐dimensional (1D) drift‐diffusion (DD) model for the charge carrier dynamics with a three‐dimensional (3D) master equation (ME) model describing the exciton dynamics in a multilayer OLED stack with an additional coupling to a thin‐film optics solver. This approach effectively combines the computational efficiency of the 1D DD solver with the physical accuracy of a discrete 3D ME model, where excitonic long‐range interactions for energy transfer can be taken into account. The coupling is established through different possible charge recombination types as well as the carrier densities themselves. We show that such a hybrid approach can efficiently and accurately describe steady‐state and transient behavior of optoelectronic devices reported in literature. Such a tool will facilitate the optimization and characterization of multilayer OLEDs and other organic semiconductor devices.     

Zum nachträglichen Kürzen und Verankern von glatten Spanngliedern im Verbund

Investigations on the Cutting and Anchoring of Existing Prestressed Concrete Beams Post Tensioned with Smooth Bars SSB has planned to provide a new lift arrangement for an underground tram station in its existing structural system. For implementing this proposal, it is required to cut existing prestressed concrete beams which presently carry a 3‐lane road. The challenge is that tendons without ribs have to be anchored by bond strength of concrete. Therefore, first of all the bond behavior had to be studied and alternatively a new anchorage device was developed. Besides laboratory tests on bond behavior, one of the prestressing cables in the existing structure was cut at midspan, on which a number of strain gages were pasted in the anchorage zone near the cutting point in advance. Hence, a long‐term monitoring of strain release was carried out under service traffic load as well as under a special static load (48t crane). It was also possible to show, that, under non static loading the anchorage of the prestressing force could be ensured only by bond. Using the results obtained from the push‐in tests for the bond behavior, the results of the field test could be predicted very well. Furthermore, laboratory tests for the new anchorage device under static and cyclic loading were performed. The results show the feasibility of the proposed procedure. The test programme was rounded off by numerical investigations on the stresses in the anchorage zone.