383 research outputs found
DWBA analysis of the 13C(6Li,d)17O reaction at 10 MeV/nucleon and its astrophysical implications
The value of the alpha spectroscopic factor (S_alpha) of the 6.356 MeV 1/2+
state of 17O is believed to have significant astrophysical implications due to
the importance of the 13C(alpha,n)16O reaction as a possible source of neutron
production for the s process. To further study this effect, an accurate
measurement of the 13C(6Li,d)17O reaction at E_lab = 60 MeV has been performed
recently by Kubono et al., who found a new value for the spectroscopic factor
of the 6.356 MeV 1/2+ state of 17O based on a distorted wave Born approximation
(DWBA) analysis of these data. This new value, S_alpha approximately = 0.011,
is surprisingly much smaller than those used previously in astrophysical
calculations (S_alpha approximately = 0.3-0.7) and thus poses a serious
question as to the role of the 13C(alpha,n)16O reaction as a source of neutron
production. In this work we perform a detailed analysis of the same
13C(6Li,d)17O data within the DWBA as well as the coupled reaction channel
(CRC) formalism. Our analysis yields an S_alpha value of over an order of
magnitude larger than that of Kubono et al. for the 6.356 MeV 1/2+ state of
17O.Comment: 17 pages, 4 figures, minor changes, accepted by Nuclear Physics
Comparison of Solar Fine Structure Observed Simultaneously in Ly-{\alpha} and Mg II h
The Chromospheric Lyman Alpha Spectropolarimeter (CLASP) observed the Sun in
H I Lyman-{\alpha} during a suborbital rocket flight on September 3, 2015. The
Interface Region Imaging Telescope (IRIS) coordinated with the CLASP
observations and recorded nearly simultaneous and co-spatial observations in
the Mg II h&k lines. The Mg II h and Ly-{\alpha} lines are important
transitions, energetically and diagnostically, in the chromosphere. The
canonical solar atmosphere model predicts that these lines form in close
proximity to each other and so we expect that the line profiles will exhibit
similar variability. In this analysis, we present these coordinated
observations and discuss how the two profiles compare over a region of quiet
sun at viewing angles that approach the limb. In addition to the observations,
we synthesize both line profiles using a 3D radiation-MHD simulation. In the
observations, we find that the peak width and the peak intensities are well
correlated between the lines. For the simulation, we do not find the same
relationship. We have attempted to mitigate the instrumental differences
between IRIS and CLASP and to reproduce the instrumental factors in the
synthetic profiles. The model indicates that formation heights of the lines
differ in a somewhat regular fashion related to magnetic geometry. This
variation explains to some degree the lack of correlation, observed and
synthesized, between Mg II and Ly-{\alpha}. Our analysis will aid in the
definition of future observatories that aim to link dynamics in the
chromosphere and transition region.Comment: Accepted by Ap
A multi-detector array for high energy nuclear e+e- pair spectrosocopy
A multi-detector array has been constructed for the simultaneous measurement
of energy- and angular correlation of electron-positron pairs produced in
internal pair conversion (IPC) of nuclear transitions up to 18 MeV. The
response functions of the individual detectors have been measured with
mono-energetic beams of electrons. Experimental results obtained with 1.6 MeV
protons on targets containing B and F show clear IPC over a wide
angular range. A comparison with GEANT simulations demonstrates that angular
correlations of pairs of transitions in the energy range between 6 and
18 MeV can be determined with sufficient resolution and efficiency to search
for deviations from IPC due to the creation and subsequent decay into
of a hypothetical short-lived neutral boson.Comment: 20 pages, 8 figure
DNA-cellulose: an economical, fully recyclable and highly effective chiral biomaterial for asymmetric catalysis
similarity_check: This document is Similarity Check deposited related_data: Supplementary Information copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal peer_review_method: Single-blind history: Received 20 December 2014; Accepted 11 January 2015; Accepted Manuscript published 14 January 2015; Advance Article published 23 January 2015; Version of Record published 24 March 2015This research was supported by the Ministe`re de l’Enseignement
Supe´rieur et de la Recherche and the Agence Nationale de
la Recherche (NCiS; ANR-2010-JCJC-715-1)
First principles calculation of structural and magnetic properties for Fe monolayers and bilayers on W(110)
Structure optimizations were performed for 1 and 2 monolayers (ML) of Fe on a
5 ML W(110) substrate employing the all-electron full-potential linearized
augmented plane-wave (FP-LAPW) method. The magnetic moments were also obtained
for the converged and optimized structures. We find significant contractions
( 10 %) for both the Fe-W and the neighboring Fe-Fe interlayer spacings
compared to the corresponding bulk W-W and Fe-Fe interlayer spacings. Compared
to the Fe bcc bulk moment of 2.2 , the magnetic moment for the surface
layer of Fe is enhanced (i) by 15% to 2.54 for 1 ML Fe/5 ML W(110), and
(ii) by 29% to 2.84 for 2 ML Fe/5 ML W(110). The inner Fe layer for 2
ML Fe/5 ML W(110) has a bulk-like moment of 2.3 . These results agree
well with previous experimental data
Monte Carlo Simulation of Magnetization Reversal in Fe Sesquilayers on W(110)
Iron sesquilayers grown at room temperature on W(110) exhibit a pronounced
coercivity maximum near a coverage of 1.5 atomic monolayers. On lattices which
faithfully reproduce the morphology of the real films, a kinetic Ising model is
utilized to simulate the domain-wall motion. Simulations reveal that the
dynamics is dominated by the second-layer islands, which act as pinning
centers. The simulated dependencies of the coercivity on the film coverage, as
well as on the temperature and the frequency of the applied field, are very
similar to those measured in experiments. Unlike previous micromagnetic models,
the presented approach provides insight into the dynamics of the domain-wall
motion and clearly reveals the role of thermal fluctuations.Comment: Final version to appear in Phys. Rev. B. References to related works
added. 7 pages, 5 figures, RevTex, mpeg simulations available at
http://www.scri.fsu.edu/~rikvol
Integrated liquid-core optical fibers --- ultra-efficient nonlinear liquid photonics
We have developed a novel integrated platform for liquid photonics based on
liquid core optical fiber (LCOF). The platform is created by fusion splicing
liquid core optical fiber to standard single-mode optical fiber making it fully
integrated and practical - a major challenge that has greatly hindered progress
in liquid-photonic applications. As an example, we report here the realization
of ultralow threshold Raman generation using an integrated CS2 filled LCOF
pumped with sub-nanosecond pulses at 1064nm and 532nm. The measured energy
threshold for the Stokes generation is ~ 1nJ, about three orders of magnitude
lower than previously reported values in the literature for hydrogen gas. The
integrated LCOF platform opens up new possibilities for ultralow power
nonlinear optics such as efficient white light generation for displays, mid-IR
generation, slow light generation, parametric amplification, all-optical
switching and wavelength conversion using liquids that have orders of magnitude
larger optical nonlinearities compared with silica glass.Comment: 4 pages, 3 figure
Expanding biohybrid-mediated asymmetric catalysis into the realm of RNA
crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 2016crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 2016crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 2016crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 2016crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 201
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