Final scientific and technical report for grant DE-AI02-93ER40784: Fundamental Physics with Cold Neutrons

There have been a growing number of notable results in fundamental neutron physics, which are briefly summarized

How child‐centred education favours some learners more than others

Debates on how best to educate young children have been raging over the last 100 years—more often fuelled by ideological preferences rather than empirical evidence. To some extent this is hardly surprising given the difficulty of examining pupil progress in a systematic and comparative way. However, the introduction of a new child‐centred curriculum in Wales provides the opportunity to undertake just such an examination. The Foundation Phase curriculum, introduced in 2008, is designed to provide all 3‐ to 7‐year‐olds with a developmental, experiential, play‐based approach to learning. Evidence from a major 3‐year evaluation of this intervention finds that, overall, pupil progress and well‐being is fostered in those settings where the principles of the Foundation Phase have been most closely followed. However, the evidence also suggests that even within these contexts, progress is uneven and that some kinds of children seem to gain more from this approach than others. The ‘losers’ appear to be boys and those living in poverty. Drawing on the theories of Basil Bernstein, the paper explores why this may be the case and examines the relative significance of teacher dispositions, teacher–learner dynamics and the availability of resources. The paper concludes by arguing that these issues will need to be addressed if the benefits of child‐centred approaches are to benefit all

Observation of the radiative decay mode of the free neutron

The theory of quantum electrodynamics (QED) predicts that beta decay of the neutron into a proton, electron and antineutrino should be accompanied by a continuous spectrum of soft photons. While this inner bremsstrahlung branch has been previously measured in nuclear beta and electron capture decay, it has never been observed in free neutron decay. Recently, the photon energy spectrum and branching ratio for neutron radiative decay have been calculated using two approaches: a standard QED framework(1-3) and heavy baryon chiral perturbation theory(4) (an effective theory of hadrons based on the symmetries of quantum chromodynamics). The QED calculation treats the nucleons as point-like, whereas the latter approach includes the effect of nucleon structure in a systematic way. Here we observe the radiative decay mode of free neutrons, measuring photons in coincidence with both the emitted electron and proton. We determined a branching ratio of (3.13 +/- 0.34) x 10(-3) (68 per cent level of confidence) in the energy region between 15 and 340 keV, where the uncertainty is dominated by systematic effects. The value is consistent with the predictions of both theoretical approaches; the characteristic energy spectrum of the radiated photons, which differs from the uncorrelated background spectrum, is also consistent with the calculated spectrum. This result may provide opportunities for more detailed investigations of the weak interaction processes involved in neutron beta decay.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62639/1/nature05390.pd

Searching for time reversal invariance violation in polarized neutron decay

Time reversal invariance violation is tightly constrained in the Standard Model, and the existence of a T-violating effect above the predicted level would be an indication of new physics. A sensitive probe of this symmetry in the weak interaction is the measurement of the D-coefficient in neutron decay. This parameter characterizes the triple-correlation of neutron spin, electron momentum, and neutrino (or proton) momentum, which changes sign under time reversal. The emiT experiment, now on line, attempts to improve the measurement of D,D, whose current average is 0.3±1.5×10−3.0.3±1.5×10−3. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87907/2/399_1.pd

Final scientific and technical report for grant DE-AI02-93ER40784: Fundamental Physics with Cold Neutrons

There have been a growing number of notable results in fundamental neutron physics, which are briefly summarized

Precision neutron flux measurement using the Alpha-Gamma device

The Alpha-Gamma device at the National Institute of Standards and Technology (NIST) utilizes neutron capture on a totally absorbing 10B deposit to measure the absolute neutron flux of a monochromatic cold neutron beam. Gammas produced by the boron capture are counted using high purity germanium detectors, which are calibrated using a well-measured 239Pu alpha source and the alpha-to-gamma ratio from neutron capture on a thin 10B target. This device has been successfully operated and used to calibrate the neutron flux monitor for the BL2 neutron lifetime experiment at NIST. It is also being used for a measurement of the 6Li(n,t)4He cross section. We shall present its principle of operation along with the current and planned projects involving the Alpha-Gamma device, including the recalibration of the U.S. national neutron standard NBS-1 and (n,f) cross section measurements of 235U

Precision neutron flux measurement using the Alpha-Gamma device

The Alpha-Gamma device at the National Institute of Standards and Technology (NIST) utilizes neutron capture on a totally absorbing 10B deposit to measure the absolute neutron flux of a monochromatic cold neutron beam. Gammas produced by the boron capture are counted using high purity germanium detectors, which are calibrated using a well-measured 239Pu alpha source and the alpha-to-gamma ratio from neutron capture on a thin 10B target. This device has been successfully operated and used to calibrate the neutron flux monitor for the BL2 neutron lifetime experiment at NIST. It is also being used for a measurement of the 6Li(n,t)4He cross section. We shall present its principle of operation along with the current and planned projects involving the Alpha-Gamma device, including the recalibration of the U.S. national neutron standard NBS-1 and (n,f) cross section measurements of 235U

In defence of generalized Darwinism

The original publication is available at: www.springerlink.com Copyright SpringerDarwin himself suggested the idea of generalizing the core Darwinian principles to cover the evolution of social entities. Also in the nineteenth century, influential social scientists proposed their extension to political society and economic institutions. Nevertheless, misunderstanding and misrepresentation have hindered the realization of the powerful potential in this longstanding idea. Some critics confuse generalization with analogy. Others mistakenly presume that generalizing Darwinism necessarily involves biological reductionism. This essay outlines the types of phenomena to which a generalized Darwinism applies, and upholds that there is no reason to exclude social or economic entities. © 2008 Springer-Verlag.Peer reviewe

The acquisition of Japanese modality during the study abroad

This chapter approaches modality from a developmental perspective in the context of second language acquisition. Specifically, it reports the results of a study that examined the development of modal expressions among five students who studied in Japan for one academic year. The study compared the students’ use of modal expressions in oral interviews before and after their study-abroad experience. The recent advancement of foreign/second language pragmatics research sheds some light on how second language learners acquire pragmatic competence, that is, the knowledge/ability necessary for using a target language appropriately (Kasper and Blum-Kulka 1993, Barron 2003). Many of these studies employ a method that elicits the performance of speech acts such as request and apology in constructed role-play situations. However, since the main focus of these studies is on general pragmatic competence, only a peripheral attention is paid to modality