381 research outputs found
Quantum well devices for mode-locking fibre lasers
The generation of picosecond duration pulses in the 1.55 micron wavelength region is of considerable interest for applications related to telecommunications. In the 1.06 micron region, picosecond pulses are useful for spectroscopy and the electro-optic sampling of high speed integrated circuits [I]. Passive mode-locking of fibre lasers using multiple quantum well (MQW) material can provide optical pulses with picosecond durations in both these wavelength regions. The optical confinement and long lengths available, give doped fibre lasers high gain together with flexibility in physical configuration. The use of QWs with light incident perpendicular to the epitaxial layers, as passive saturable absorbers to mode-lock these lasers, is attractive because of their polarisation insensitivity and the wide range of wavelengths available. The semiconductor sample operating wavelength is governed by the materials, their compositions and dimensions used. In fibre, gain is provided in the 1.55 micron region by doping with Erbium whilst Neodymium is used for operation in the 1.06 micron region. By integrating the saturable absorber and laser-cavity end mirror into a single semiconductor device we have generated picosecond pulses in very simple cavity configurations
Strong Decays of Strange Quarkonia
In this paper we evaluate strong decay amplitudes and partial widths of
strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give
numerical results for all energetically allowed open-flavor two-body decay
modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and
1F multiplets, comprising strong decays of a total of 43 resonances into 525
two-body modes, with 891 numerically evaluated amplitudes. This set of
resonances includes all strange qqbar states with allowed strong decays
expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic
quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical
results for all amplitudes present in each decay mode. We also discuss the
status of the associated experimental candidates, and note which states and
decay modes would be especially interesting for future experimental study at
hadronic, e+e- and photoproduction facilities. These results should also be
useful in distinguishing conventional quark model mesons from exotica such as
glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table
Molecular and Historical Aspects of Corn Belt Dent Diversity
Tens-of-thousands of open-pollinated cultivars of corn (Zea mays L.) are being maintained in germplasm banks. Knowledge of the amount and distribution of genetic variation within and among accessions can aid end users in choosing among them. We estimated molecular genetic variation and looked for influences of pedigree, adaptation, and migration in the genetic makeup of conserved Corn-Belt Dent-related germplasm. Plants sampled from 57 accessions representing Corn-Belt Dents, Northern Flints, Southern Dents, plus 12 public inbreds, were genotyped at 20 simple sequence repeat (SSR) loci. For 47 of the accessions, between 5 and 23 plants per accession were genotyped (mean = 9.3). Mean number of alleles per locus was 6.5 overall, 3.17 within accessions, and 3.20 within pooled inbreds. Mean gene diversity was 0.53 within accessions and 0.61 within pooled inbreds. Open-pollinated accessions showed a tendency toward inbreeding (FIS = 0.09), and 85% of genetic variation was shared among them. A Fitch-Margoliash tree strongly supported the distinctiveness of flint from dent germplasm but did not otherwise reveal evidence of genetic structure. Mantel tests revealed significant correlations between genetic distance and geographical (r = 0.54, P= 0.04) or maturity zone (r = 0.33, P = 0.03) distance only if flint germplasm was included in the analyses. A significant correlation (r = 0.76, P \u3c 0.01) was found between days to pollen shed and maturity zone of accession origin. Pedigree, rather than migration or selection, has most influenced the genetic structure of the extant representatives of the open-pollinated cultivars at these SSR loci
A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007
We present the results of the first search for gravitational wave bursts
associated with high energy neutrinos. Together, these messengers could reveal
new, hidden sources that are not observed by conventional photon astronomy,
particularly at high energy. Our search uses neutrinos detected by the
underwater neutrino telescope ANTARES in its 5 line configuration during the
period January - September 2007, which coincided with the fifth and first
science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed
for candidate gravitational-wave signals coincident in time and direction with
the neutrino events. No significant coincident events were observed. We place
limits on the density of joint high energy neutrino - gravitational wave
emission events in the local universe, and compare them with densities of
merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at
http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000
Longitudinal data assessment of global stability index in kale leaves
ABSTRACT Kale plants are usually sold “in natura” in street markets and malls. Kale leaves can have their appearance compromised by dehydration and discoloration due to increased post-harvest time exposure. We aimed to analyze the Global Stability Index (GSI) in kale accessions by means of repeated measurement analysis and curve grouping as a complementary form of superior sample identification with regard to post-harvest preservation. Thirty kale accessions were evaluated using a randomized block design with four blocks and five plants per plot. Two commercial leaves per plant were collected, and kept on workbenches in the shade at a temperature of 18 ± 1 °C. Subsequently, the degrees of discoloration and dehydration, total chlorophyll content, and accumulated fresh mass loss were evaluated over a 15-day period. From these data, the GSI was calculated for each day of evaluation. In addition, using mixed models, thirteen co-variance structures were tested. For graphical analysis, thirteen linear and non-linear models were assessed followed by curve grouping using multivariate analysis. The GSI was efficient for differentiating accessions, which became an important tool in post-harvest studies. GSI values were not equally correlated, therefore the use of mixed models became an important approach. The unstructured matrix was the best fit to model the dependence of error. The Melow I model was the best fit for studying the GSI. The accessions UFVJM-10, UFLA-1, COM-1, UFVJM-32, COM-3, UFVJM-8, UFVJM-36 and UFVJM-24, belonging to 3 and 5 clusters, are recommended for crop cultivation and as parental material in breeding programs
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
What Drives Fitness Apps Usage? An Empirical Evaluation
Part 3: Creating Value through ApplicationsInternational audienceThe increased health problems associated with lack of physical activity is of great concern around the world. Mobile phone based fitness applications appear to be a cost effective promising solution for this problem. The aim of this study is to develop a research model that can broaden understanding of the factors that influence the user acceptance of mobile fitness apps. Drawing from Unified Theory of Acceptance and Use of Technology (UTAUT) and Elaboration Likelihood Model (ELM), we conceptualize the antecedents and moderating factors of fitness app use. We validate our model using field survey. Implications for research and practice are discussed
Exotic state photoproduction
It is shown that the list of unusual mesons planned for a careful study in
photoproduction can be extended by the exotic states with which should be looked for in the decay
channels in the reactions and . The full classification of the states by their
quantum numbers is presented. A simple model for the spin structure of the , , and reaction amplitudes is formulated and the tentative estimates of the
corresponding cross sections at the incident photon energy
GeV are obtained: b, b, b, and b. The problem of the
signal extraction from the natural background due to the other production channels is discussed. In particular the estimates are
presented for the , , and reaction cross sections.
Our main conclusion is that the search for the exotic
states is quite feasible at JEFLAB facility. The expected yield of the events in a 30-day run at the 100% detection
efficiency approximates events.Comment: 19 pages, revtex, 1 figure in postscipt, some comments and references
added, a few minor typos corrected, to be published in Phys. Rev.
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