25 research outputs found
Cost effective flat plate photovoltaic modules using light trapping
Work in optical trapping in 'thick films' is described to form a design guide for photovoltaic engineers. A thick optical film can trap light by diffusive reflection and total internal reflection. Light can be propagated reasonably long distances compared with layer thicknesses by this technique. This makes it possible to conduct light from inter-cell and intra-cell areas now not used in photovoltaic modules onto active cell areas
A unitary model for meson-nucleon scattering
In an effective Lagrangian model employing the K-matrix approximation we
extract nucleon resonance parameters. To this end we analyze simultaneously all
available data for reactions involving the final states , ,
and in the energy range GeV. The background contributions are generated consistently from the
relevant Feynman amplitudes, thus significantly reducing the number of free
parameters.Comment: Revised version. 60 pages, 17 figures. Two figures and a short
discussion (\pi N \to \eta N, K \Lambda amplitudes) added, typos and minor
errors in the citations correcte
Production of Lambda and Sigma^0 hyperons in proton-proton collisions
This paper reports results on simultaneous measurements of the reaction
channels pp -> pK+\Lambda and pp -> pK+\Sigma^0 at excess energies of 204, 239,
and 284 MeV (\Lambda) and 127, 162, and 207 MeV (\Sigma^0). Total and
differential cross sections are given for both reactions. It is concluded from
the measured total cross sections that the high energy limit of the cross
section ratio is almost reached at an excess energy of only about 200 MeV. From
the differential distributions observed in the overall CMS as well as in the
Jackson and helicity frames, a significant contribution of interfering nucleon
resonances to the \Lambda production mechanism is concluded while resonant
\Sigma^0-production seems to be of lesser importance and takes place only
through specific partial waves of the entrance channel. The data also indicate
that kaon exchange plays a minor role in the case of \Lambda- but an important
role for \Sigma^0-production. Thus the peculiar energy dependence of the
\Lambda-to-\Sigma^0 cross section ratio appears in a new light as its
explanation requires more than mere differences between the p\Lambda and the
p\Sigma^0 final state interaction. The data provide a benchmark for theoretical
models already available or yet to come.Comment: 18 pages, 10 figures; accepted by The European Physical Journal A
(EPJ A
Good for your soul? Adult learning and mental well-being
Although there is a widely held view that adult learning has a positive impact on well-being, only recently has this proposition been systematically tested. The paper reviews recent research findings on the influence of adult learning on earnings and employability, both of which may influence well-being indirectly. These are more important for some groups than others: in economically advanced societies, additional earnings produce limited gains in well-being for most groups except the poorest, while employability is most significant for groups that are most vulnerable in the labour market. The author then reviews recent research findings showing that participating in learning in adult life has some positive direct influence on well-being; analyses of cohort studies suggest that the influence is comparatively small, but nevertheless significant. There has been less study of learning’s negative consequences for well-being, and the paper draws on history data to illustrate some of these less desirable influences. It concludes by identifying areas for further research, and outlining a number of implications for policy and practice. These are particularly important in the current context, where environmental movements appear to be challenging the primacy of economic growth as the overarching goal of policy
P-wave excited baryons from pion- and photo-induced hyperon production
We report evidence for , , ,
, , and , and find
indications that might have a companion state at 1970\,MeV. The
controversial is not seen. The evidence is derived from a
study of data on pion- and photo-induced hyperon production, but other data are
included as well. Most of the resonances reported here were found in the
Karlsruhe-Helsinki (KH84) and the Carnegie-Mellon (CM) analyses but were
challenged recently by the Data Analysis Center at GWU. Our analysis is
constrained by the energy independent scattering amplitudes from either
KH84 or GWU. The two amplitudes from KH84 or GWU, respectively, lead to
slightly different branching ratios of contributing resonances but the
debated resonances are required in both series of fits.Comment: 22 pages, 28 figures. Some additional sets of data are adde
Nucleon resonances in the fourth resonance region
Nucleon and resonances in the fourth resonance region are studied in
a multichannel partial-wave analysis which includes nearly all available data
on pion- and photo-induced reactions off protons. In the high-mass range, above
1850\,MeV, several alternative solutions yield a good description of the data.
For these solutions, masses, widths, pole residues and photo-couplings are
given. In particular, we find evidence for nucleon resonances with
spin-parities . For one set of solutions, there are four
resonances forming naturally a spin-quartet of resonances with orbital angular
momentum L=2 and spin S=3/2 coupling to . Just below 1.9\,GeV we
find a spin doublet of resonances with and . Since a spin
partner with is missing at this mass, the two resonances form a
spin doublet which must have a symmetric orbital-angular-momentum wave function
with L=1. For another set of solutions, the four positive-parity resonances are
accompanied by mass-degenerate negative-parity partners -- as suggested by the
conjecture of chiral symmetry restoration. The possibility of a spin doublet at 1900\,MeV belonging to a 20-plet is discussed.Comment: 16 page
Properties of baryon resonances from a multichannel partial wave analysis
Properties of nucleon and resonances are derived from a multichannel
partial wave analysis. The statistical significance of pion and photo-induced
inelastic reactions off protons are studied in a multichannel partial-wave
analysis.Comment: 12 pages, 8 Table