Gold charge state distributions in highly ionized, low-density beam plasmas

We present a systematic study of Au charge state distributions (CSDs) from low density, nonlocal thermodynamic equilibrium plasmas created in the Livermore electron beam ion traps (EBIT-I and EBIT-II). X-ray emission from Ni-like to Kr-like Au ions has been recorded from monoenergetic electron beam plasmas having E(beam)=2.66, 2.92, 3.53, and 4.54 keV, and the CSDs of the beam plasmas have been inferred by fitting the collisionally excited line transitions and radiative recombination emission features with synthetic spectra. We have modeled the beam plasmas using a collisional-radiative code with various treatments of the atomic structure for the complex M- and N-shell ions and find that only models with extensive doubly excited states can properly account for the dielectronic recombination (DR) channels that control the CSDs. This finding would be unremarkable for plasmas with thermal electron distributions, where many such states are sampled, and the importance of DR is well established. But in an EBIT source, the beam is resonant with only a subset of such states having spectator electrons in orbitals with high principal quantum number n (8≤n≤20). The inclusion of such states in the model was also necessary to obtain agreement with observed stabilizing transitions in the x-ray spectra.

The nonmedical use of prescription stimulants among dental and dental hygiene students

The purpose of this study was to determine the nonmedical use of prescription attention deficit disorder (ADD) stimulant medication among dental and dental hygiene students. A questionnaire was used to examine demographic information, student experiences, and perceptions of prescription stimulant medication and to determine if students used a prescription stimulant nonmedically. In 2008, 401 surveys were mailed to dental education institutions in the south-central region of the United States, and 243 surveys (61 percent) were returned. The survey found that 12.4 percent of these students used a prescription stimulant nonmedically and, of those, 70 percent took it to improve attention and/or concentration. The most commonly reported stimulant medication used nonmedically was Adderall (77 percent). The majority (87 percent) of the students obtained the medication through friends, and 90 percent began using the drug in college. Even though 74 percent of the students reported being stressed, chi-square analysis found no significant association between nonmedical use of ADD stimulant medication and stress level (p=0.585). Sixteen percent of the students surveyed felt it was easy to obtain stimulant medication for nonmedical use at their school, and 17 percent thought it was a problem within their institution. These results may help administrators and faculty members become aware of potential problems with the misuse of ADD stimulant medication.

Beyond fast mapping: young children's extensions of novel words and novel facts

L. Markson and P. Bloom (1997) concluded that there was evidence against a dedicated system for word learning on the basis of their finding that children remembered a novel word and a novel fact equally well. However, a word-learning system involves more than recognition memory; it must also provide a means to guide the extension of words to additional exemplars, and words and facts may differ with regard to extendibility. Two studies are reported in which 2-4-year-old children learned novel words and novel facts for unfamiliar objects and then were asked to extend the words and facts to additional exemplars of the training objects. In both studies, children extended the novel word to significantly more category members than they extended the novel fact. The results show that by 2 years of age, children honor the necessary extendibility of novel count nouns but are uncertain about the extendibility of arbitrary facts.