235 research outputs found
The role of C2 in nanocrystalline diamond growth
This paper presents findings from a study of nanocrystalline diamond (NCD)
growth in a microwave plasma chemical vapour deposition (CVD) reactor. NCD
films were grown using Ar/H2/CH4 and He/H2/CH4 gas compositions. The resulting
films were characterised using Raman spectroscopy, scanning electron microscopy
and atomic force microscopy. Analysis revealed an estimated grain size of the
order of 50 nm, growth rates in the range 0.01 to 0.3 um/h and sp3 and sp2
bonded carbon content consistent with that expected for NCD. The C2 Swan band
was probed using cavity ring-down spectroscopy (CRDS) to measure the absolute
C2 (a) number density in the plasma during diamond film growth. The number
density in the Ar/H2/CH4 plasmas was in the range 2 to 4 x 10^12 cm-3, but
found to be present in quantities too low to measure in the He/H2/CH4 plasmas.
Optical emission spectrometry (OES) was employed to determine the relative
densities of the C2 excited state (d) in the plasma. The fact that similar NCD
material was grown whether using Ar or He as the carrier gas suggests that C2
does not play a major role in the growth of nanocrystalline diamond.Comment: 39 pages, 11 figure
Eclipsing Binaries in Open Clusters
Detached eclipsing binaries are very useful objects for calibrating
theoretical stellar models and checking their predictions. Detached eclipsing
binaries in open clusters are particularly important because of the additional
constraints on their age and chemical composition from their membership of the
cluster. I compile a list containing absolute parameters of well-studied
eclipsing binaries in open clusters, and present new observational data on the
B-type systems V1481 Cyg and V2263 Cyg which are members of the young open
cluster NGC 7128.Comment: 4 pages, 2 colour figures. Poster presentation for IAUS 240 (Binary
Stars as Critical Tools and Tests in Contemporary Astrophysics), Prague,
August 2006. The poster itself can be dowloaded in ppt and pdf versions from
http://www.astro.keele.ac.uk/~jkt/pubs.htm
A wider Europe? The view from Russia, Belarus and Ukraine
On the evidence of national surveys conducted between 2000 and 2006, there is a declining sense of European self-identity in the three Slavic post-Soviet republics of Russia, Belarus and Ukraine. Attitudes towards the European Union and the possibility of membership are broadly supportive, but with a substantial proportion who find it difficult to express a view, and substantial proportions are poorly informed in comparison with the general public in EU member or prospective member countries. Those who are better informed are more likely to favour EU membership and vice versa. Generally, socioeconomic characteristics (except for age and region) are relatively poor predictors of support for EU membership as compared with attitudinal variables. But ‘Europeanness’ should not be seen as a given, and much will depend on whether EU member countries emphasize what is common to east and west or establish ‘new dividing lines’ in place of those of the cold war
Limits on the monopole magnetic field from measurements of the electric dipole moments of atoms, molecules and the neutron
A radial magnetic field can induce a time invariance violating electric
dipole moment (EDM) in quantum systems. The EDMs of the Tl, Cs, Xe and Hg atoms
and the neutron that are produced by such a field are estimated. The
contributions of such a field to the constants, of the T,P-odd
interactions and are also estimated for the TlF, HgF and YbF molecules (where
() is the electron (nuclear) spin and is the molecular
axis). The best limit on the contact monopole field can be obtained from the
measured value of the Tl EDM. The possibility of such a field being produced
from polarization of the vacuum of electrically charged magnetic monopoles
(dyons) by a Coulomb field is discussed, as well as the limit on these dyons.
An alternative mechanism involves chromomagnetic and chromoelectric fields in
QCD.Comment: Uses RevTex, 16 pages, 4 postscript figures. An explanation of why
there is no orbital contribution to the EDM has been added, and the
presentation has been improved in genera
SS Ari: a shallow-contact close binary system
Two CCD epochs of light minimum and a complete R light curve of SS Ari are
presented. The light curve obtained in 2007 was analyzed with the 2003 version
of the W-D code. It is shown that SS Ari is a shallow contact binary system
with a mass ratio and a degree of contact factor f=9.4(\pm0.8%). A
period investigation based on all available data shows that there may exist two
distinct solutions about the assumed third body. One, assuming eccentric orbit
of the third body and constant orbital period of the eclipsing pair results in
a massive third body with and P_3=87.00.278M_{\odot}$. Both of the cases
suggest the presence of an unseen third component in the system.Comment: 28 pages, 9 figures and 5 table
Double strand breaks in DNA resulting from double-electron-emission events
A mechanism of double strand breaking (DSB) in DNA due to the action of two
electrons is considered. These are the electrons produced in the vicinity of
DNA molecules due to ionization of water molecules with a consecutive emission
of two electrons, making such a mechanism possible. This effect qualitatively
solves a puzzle of large yields of DSBs following irradiation of DNA molecules.
The transport of secondary electrons, including the additional electrons, is
studied in relation to the assessment of radiation damage due to incident ions.
This work is a stage in the inclusion of Auger mechanism and like effects into
the multiscale approach to ion-beam cancer therapy.Comment: 4 pages, 3 figure
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