Simulation Studies of Delta-ray Backgrounds in a Compton-Scatter Transition Radiation Detector

In order to evaluate the response to cosmic-ray nuclei of a Compton-Scatter Transition Radiation Detector in the proposed ACCESS space-based mission, a hybrid Monte Carlo simulation using GEANT3 and an external transition radiation (TR) generator routine was constructed. This simulation was employed to study the effects of delta-ray production induced by high-energy nuclei and to maximize the ratio of TR to delta-ray background. The results demonstrate the ability of a Compton-Scatter Transition Radiation Detector to measure nuclei from boron to iron up to Lorentz factors ~ 10^5 taking into account the steeply falling power-law cosmic ray spectra.Comment: Presented at TRDs for the 3rd millennium: Third Workshop on advanced Transition Radiation Detectors for accelerator and space applications, Ostuni, Italy, September 2005, 4 pages, 2 figure

Compton Scattered Transition Radiation from Very High Energy Particles

X-ray transition radiation can be used to measure the Lorentz factor of relativistic particles. At energies approaching gamma = E/mc^2 = 10^5, transition radiation detectors (TRDs) can be optimized by using thick (sim 5 - 10 mil) foils with large (5-10 mm) spacings. This implies X-ray energies >100 keV and the use of scintillators as the X-ray detectors. Compton scattering of the X-rays out of the particle beam then becomes an important effect. We discuss the design of very high energy detectors, the use of metal radiator foils rather than the standard plastic foils, inorganic scintillators for detecting Compton scattered transition radiation, and the application to the ACCESS cosmic ray experiment.Comment: To be published, Astroparticle Physic

South Africa : serious about biodiversity science

The original publication is available at http://www.plosbiology.orgIn 1772, Carolus Linnaeus wrote a letter, now oft-quoted, to Ryk Tulbagh, the Governor of the Cape—in which he envied Tulbagh’s “sovereign control of that Paradise on Earth, the Cape of Good Hope, which the benefi cent Creator has enriched with his choicest wonders”. Two and a half centuries later, South Africa’s biodiversity remains a great source of interest to the scientifi c community—and for good reason. Plant biodiversity, with over 20 000 different species, is in the foreground: South Africa, which comprises less than 1% of the world’s land surface, contains 8% of its plant species. Perhaps less well known is that the country also contains 7% of all bird, mammal, and reptile species, and 15% of known coastal marine species.Publishers' Versio

Investigating Behavioral Responses to Positive Inducements for Filing Tax Returns

A significant amount of non-compliance associated with the personal income tax is due to the taxpayers who are not “in the system,” not having filed a tax return in the recent past or perhaps ever. We use experimental laboratory methods to examine two types of positive incentives for filing tax returns: tax credits and social safety net benefits, both of which are conditional on tax filing. Our experimental design captures the essential features of the voluntary income reporting and tax assessment system used in many countries. Human participants in a controlled laboratory environment earn income through their performance in a task. The participants must then decide whether to file a tax return and, conditional upon filing, how much income to report. Taxes are paid on reported income only. Unreported income of filers may be discovered via a random audit, and the participant must then pay the owed taxes plus a fine based on the unpaid taxes; non-filers are not subject to an audit. Inducements for filing are introduced in several alternative treatments. In one treatment we introduce a social safety net (e.g., unemployment replacement income) that is conditional on past filing behavior. In a second treatment we introduce tax credits that are available either to low income participants or to all income levels, but again only to those who file a tax return. Our results suggest that a tax credit increases filing but only if the credit is targeted to low income earners. The provision of a social safety net via unemployment benefits also has a positive, albeit indirect, impact on participation. Key Words:

Taxpayer Information Assistance Services and Tax Compliance Behavior

The traditional "enforcement" paradigm of tax administration views taxpayers as potential criminals, and emphasizes the repression of illegal behavior through frequent audits and stiff penalties. However, an important trend in tax administration policies in recent years is the recognition that this paradigm is incomplete. Instead, a revised "service" paradigm recognizes the role of enforcement, but also emphasizes the role of tax administration as a facilitator and a provider of services to taxpayer-citizens. This research utilizes laboratory experiments to test the effectiveness of such taxpayer service programs in enhancing tax compliance. Our basic experimental setting mimics the naturally occurring environment: subjects earn income, they must choose whether to file a tax return, and they then must choose how much of their net income to report to a tax authority that may audit the subject. To investigate the effects of taxpayer services, we "complicate" these compliance decisions of subjects, and then provide "services" from the "tax administration" that allow subjects to compute more easily their tax liabilities. Our results indicate that uncertainty reduces both the filing and the reporting compliance of an individual. However, we also find that agency-provided information has a positive and significant impact on the tendency of an individual to file a tax return, and also on reporting for individuals who choose to file a return.tax evasion, tax compliance, behavioral economics, experimental economics

Gonadal hormones, but not sex, affect the acquisition and maintenance of a Go/No-Go odor discrimination task in mice

In mice, olfaction is crucial for identifying social odors (pheromones) that signal the presence of suitable mates. We used a custom-built olfactometer and a thirst-motivated olfactory discrimination Go/No-Go (GNG) task to ask whether discrimination of volatile odors is sexually dimorphic and modulated in mice by adult sex hormones. Males and females gonadectomized prior to training failed to learn even the initial phase of the task, which involved nose poking at a port in one location obtaining water at an adjacent port. Gonadally intact males and females readily learned to seek water when male urine (S+) was present but not when female urine (S−) was present; they also learned the task when non-social odorants (amyl acetate, S+; peppermint, S−) were used. When mice were gonadectomized after training the ability of both sexes to discriminate urinary as well as non-social odors was reduced; however, after receiving testosterone propionate (castrated males) or estradiol benzoate (ovariectomized females), task performance was restored to pre-gonadectomy levels. There were no overall sex differences in performance across gonadal conditions in tests with either set of odors; however, ovariectomized females performed more poorly than castrated males in tests with non-social odors. Our results show that circulating sex hormones enable mice of both sexes to learn a GNG task and that gonadectomy reduces, while hormone replacement restores, their ability to discriminate between odors irrespective of the saliency of the odors used. Thus, gonadal hormones were essential for both learning and maintenance of task performance across sex and odor type.We thank David Giese for help in programming the apparatus used in GNG testing and Alberto Cruz-Martin for comments on an early version of the manuscript. This work was supported by NIDCD grant DC008962 to JAC. (DC008962 - NIDCD grant)Accepted manuscrip

Ariel - Volume 2 Number 1

Editors Delvun C. Case, Jr. Paul M. Fernhoff Associate Editors Donald Bergman Daniel B. Gould Richard Bonanno Ronald Hoffman Lay-Out Editor Carol Dolinskas Sports Editor James Nocon Business Manager Nick Grego Contributing Editors Michael J. Blecker Stephen P. Flynn Lin Sey Edwards Jack Guralnik W. Cherry Ligh