The Majorana Collaboration is operating an array of high purity Ge detectors to search for neutrinoless double-β decay in ^{76}Ge. The Majorana Demonstrator comprises 44.1 kg of Ge detectors (29.7 kg enriched in ^{76}Ge) split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Here we present results from data taken during construction, commissioning, and the start of full operations. We achieve unprecedented energy resolution of 2.5 keV FWHM at Q_{ββ} and a very low background with no observed candidate events in 9.95 kg yr of enriched Ge exposure, resulting in a lower limit on the half-life of 1.9×10^{25}  yr (90% C.L.). This result constrains the effective Majorana neutrino mass to below 240-520 meV, depending on the matrix elements used. In our experimental configuration with the lowest background, the background is 4.0_{-2.5}^{+3.1}  counts/(FWHM t yr).

Results are reported of an experimental search for the unique, rapidly varying temporal pattern of solar axions coherently converting into photons via the Primakoff effect in a single crystal germanium detector when axions are incident at a Bragg angle with a crystalline plane. The analysis of 1.94 kg yr of data from the 1 kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound by an axion-photon coupling of g agg , 2.7 3 10 29 GeV 21 , independent of axion mass up to ϳ1 keV. [S0031-9007(98)07812-0] PACS numbers: 14.80. Mz, 96.60.Vg Early QCD theories predicted a particle with the quantum numbers of the h meson, but with a mass close to that of the pion. A term added to the QCD Lagrangian to ameliorate this so-called U(1) problem violated CP invariance in strong interactions and implied a neutron electric-dipole moment about 10 9 times larger than the experimental upper bound [1]. Peccei and Quinn [2] introduced a new field causing strong CP violation to vanish dynamically. Subsequently, Weinberg [3,4] and Wilczek [5] demonstrated that the Peccei-Quinn mechanism generates a Nambu-Goldstone boson, the axion, that couples to a two-photon vertex via a coupling g agg . Axion production via the Primakoff effect occurs when a photon couples to a charge via a virtual photon, producing an axion. Detection can occur by observing photons resulting from axions coupling to electrical charges via virtual photons.The dense volume of photons and charges in the sun or any star produces conditions for axion production. The Ge detector then can act as the axion-photon converter and detector. When the characteristic wavelength of the axion satisfies a Bragg condition in the single crystal Ge detector, photon production would occur with an expected temporal pattern depending on the changing relative directions between the vectors from the solar core and the crystalline planes.Extensive reviews of axion phenomenology and their effects on stellar evolution have been given by Raffelt [6,7] who gives a bound of 10 210 GeV 21 on the coupling of axions to the two-photon vertex from the population of red giant stars. A detailed treatment of solar axions and of a proposed method of detecting them was given by van Bibber et al. [8]. Details of a theory for searching for axions with germanium detectors were recently given by Creswick et al. [9]. The objective is to detect solar axions through their coherent Primakoff conversion into photons in the lattice of a germanium crystal when the incident angle satisfies the Bragg condition. The detection rates in various energy windows are correlated with the relative orientations of the detector and the sun [9]. This correlation results in a distinctive, unique signature of the axion. In this Letter, the results of a search using a 1 kg, ultralow background germanium detector installed in the HIPARSA iron mine in Sierra Grande, Argentina, at 410 24 00 S and 65 ± 22 0 W are presented. A description of the experimental setup and detector spectrum was given earlier by Di Gregori...

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Student performance in two first-semester general chemistry courses are compared to determine whether a distance learning model can provide a comparable learning opportunity to the conventional lecture–laboratory format. The conventional course was taught at a midsized, southeastern university; the distance learning course was taught through a community college. The laboratory portion of the distance learning course consisted of at-home (kitchen chemistry) experiments. For the first two semesters (Version I), the lecture portion of the course was delivered via the Internet and the students met on campus each week for a laboratory–recitation session. For the following three semesters (Version II), all instruction was offered via the Internet. In every semester, distance learning students achieved higher average scores than their university counterparts on common final exams. In laboratory practicals, distance learners demonstrated manipulation, data analysis, and data reporting skills that surpassed those of the students in the conventional course. These results suggest that this distance learning model for teaching chemistry can be an effective alternative to conventional teaching methods for the types of students who typically succeed in a distance learning environment. The results also demonstrate a unique approach to helping students appreciate the relevance of chemistry to their daily lives.

The International Germanium Experiment (IGEX) has analyzed 117 mole yr of 76 Ge data from its isotopically enriched (86% 76 Ge) germanium detectors. Applying pulse-shape discrimination (PSD) to the more recent data, the lower bound on the half-life for neutrinoless double-beta