Studies of the dose-effect relation

Dose-effect relations and, specifically, cell survival curves are surveyed with emphasis on the interplay of the random factors — biological variability, stochastic reaction of the cell, and the statistics of energy deposition —that co-determine their shape. The global parameters mean inactivation dose, , and coefficient of variance, V, represent this interplay better than conventional parameters. Mechanisms such as lesion interaction, misrepair, repair overload, or repair depletion have been invoked to explain sigmoid dose dependencies, but these notions are partly synonymous and are largely undistinguishable on the basis of observed dose dependencies. All dose dependencies reflect, to varying degree, the microdosimetric fluctuations of energy deposition, and these have certain implications, e.g. the linearity of the dose dependence at small doses, that apply regardless of unresolved molecular mechanisms of cellular radiation action

Nuclear reaction cross sections for spacecraft shield design

Nuclear reaction cross section data for spacecraft shield design, and for determining radiation dose effect on astronaut

Processing Issues in Top-Down Approaches to Quantum Computer Development in Silicon

We describe critical processing issues in our development of single atom devices for solid-state quantum information processing. Integration of single 31P atoms with control gates and single electron transistor (SET) readout structures is addressed in a silicon-based approach. Results on electrical activation of low energy (15 keV) P implants in silicon show a strong dose effect on the electrical activation fractions. We identify dopant segregation to the SiO2/Si interface during rapid thermal annealing as a dopant loss channel and discuss measures of minimizing it. Silicon nanowire SET pairs with nanowire width of 10 to 20 nm are formed by electron beam lithography in SOI. We present first results from Coulomb blockade experiments and discuss issues of control gate integration for sub-40nm gate pitch levels

Carbohydrate Mouth Rinse Improves 1.5 h Run Performance: Is There a Dose-Effect?

There is a substantial body of recent evidence showing ergogenic effects of carbohydrate (CHO) mouth rinsing on endurance performance. However, there is a lack of research on the dose-effect and the aim of this study was to investigate the effect of two different concentrations (6% and 12% weight/volume, w/v) on 90 minute treadmill running performance. Seven active males took part in one familiarization trial and three experimental trials (90-minute self-paced performance trials). Solutions (placebo, 6% or 12% CHO-electrolyte solution, CHO-E) were rinsed in the mouth at the beginning, and at 15, 30 and 45 minutes during the run. The total distance covered was greater during the CHO-E trials (6%, 14.6 ± 1.7 km; 12%, 14.9 ± 1.6 km) compared to the placebo trial (13.9 ± 1.7 km, P 0.05). There were no between trial differences (P > 0.05) in ratings of perceived exertion (RPE) and feeling or arousal ratings suggesting that the same subjective ratings were associated with higher speeds in the CHO-E trials. Enhanced performance in the CHO-E trials was due to higher speeds in the last 30 minutes even though rinses were not provided during the final 45 minutes, suggesting the effects persist for at least 20-45 minutes after rinsing. In conclusion, mouth rinsing with a CHO-E solution enhanced endurance running performance but there does not appear to be a dose-response effect with the higher concentration (12%) compared to a standard 6% solution

Food-induced behavioral sensitization, its cross-sensitization to cocaine and morphine, pharmacological blockade, and effect on food intake

Repeated administration of abused drugs sensitizes their stimulant effects and results in a drug-paired environment eliciting conditioned activity. We tested whether food induces similar effects. Food-deprived male mice were given novel food during 30 min tests in a runway (FR group) that measured locomotor activity. Whereas the activity of this group increased with repeated testing, that of a group exposed to the runways but that received the food in the home cage (FH group), or of a group satiated by prefeeding before testing (SAT group), decreased. When exposed to the runways in the absence of food, the paired group was more active than the other groups (conditioned activity); no activity differences were seen in an alternative, non-food-paired, apparatus. Conditioned activity survived a 3-week period without runway exposure. Conditioned activity was selectively reduced by the opiate antagonist naltrexone (10-20 mg/kg) and by the noncompetitive AMPA receptor antagonist GYKI 52466 [1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride] (5-10 mg/kg). The D1 antagonist SCH23390 [R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride] (15-30 microg/kg) and D2 antagonist sulpiride (25-125 mg/kg) reduced activity nonspecifically. A single intraperitoneal dose of cocaine (10 mg/kg) or morphine (20 mg/kg) increased activity compared with saline, the stimulant effect being larger in the FR group, suggesting "cross-sensitization" to these drugs. However, pretreatment with GYKI 52466 or naltrexone at doses that suppressed conditioned activity in FR animals suppressed cross-sensitization to cocaine. When allowed ad libitum access to food in the runway, FR mice consumed more pellets in a time-limited test. Thus, many of the features of behavioral sensitization to drugs can be demonstrated using food reward and may contribute to excessive eating