31,177 research outputs found
Contrasting the beam interaction characteristics of selected lasers with a partially stabilised zirconia (PSZ) bio-ceramic
Differences in the beam interaction characteristics of a CO2 laser, a Nd:YAG laser, a high power diode laser (HPDL) and an excimer laser with a partially stabilised zirconia (PSZ) bio-ceramic have been studied. A derivative of Beer-Lambert’s law was applied and the laser beam absorption lengths of the four lasers were calculated as 33.55 x 10-3 cm for the CO2 laser, 18.22 x 10-3 cm for the Nd:YAG laser, 17.17 x 10-3 cm for the HPDL and 8.41 x 10-6 cm for the excimer laser. It was determined graphically that the fluence threshold values at which significant material removal was effected by the CO2 laser, the Nd:YAG laser, the HPDL and the excimer laser were 52 J/cm2, 97 J/cm2, 115 J/cm2 and 0.48 J/cm2 respectively. The thermal loading value for the CO2 laser, the Nd:YAG laser, the HPDL and the excimer laser were calculated as being 1.55 kJ/cm3, 5.32 kJ/cm3, 6.69 kJ/cm3 and 57.04 kJ/cm3 respectively
Studies of Heavily Ionizing Particles and Space Biology Semiannual Report
Radiobiological and radiation medical studies on biological cel
Biology and Medicine, Spring 1965 Semiannual report
Reports on radiobiology studies, pion studies with silicon detectors, immunology, ultracentrifuge rotor temperature and speed measurement by radio telemetry, and radiosensitivity investigation
Gravitino or Axino Dark Matter with Reheat Temperature as high as GeV
A new scheme for lightest supersymmetric particle (LSP) dark matter is
introduced and studied in theories of TeV supersymmetry with a QCD axion, ,
and a high reheat temperature after inflation, . A large overproduction of
axinos () and gravitinos () from scattering at , and
from freeze-in at the TeV scale, is diluted by the late decay of a saxion
condensate that arises from inflation. The two lightest superpartners are
, with mass of order the TeV scale, and with mass
anywhere between the keV and TeV scales, depending on the mediation
scale of supersymmetry breaking. Dark matter contains both warm and cold
components: for LSP the warm component arises from , while for LSP the warm component arises
from . The free-streaming scale for the warm
component is predicted to be of order 1 Mpc (and independent of in
the case of LSP). can be as high as GeV, for any
value of , solving the gravitino problem. The PQ symmetry breaking
scale depends on and and can be anywhere in the range
GeV. Detailed predictions are made for the lifetime of
the neutralino LOSP decaying to and ,
which is in the range of m over much of parameter space. For an
axion misalignment angle of order unity, the axion contribution to dark matter
is sub-dominant, except when approaches GeV.Comment: 43 pages, 16 figure
The Weak Scale from BBN
The measured values of the weak scale, , and the first generation masses,
, are simultaneously explained in the multiverse, with all these
parameters scanning independently. At the same time, several remarkable
coincidences are understood. Small variations in these parameters away from
their measured values lead to the instability of hydrogen, the instability of
heavy nuclei, and either a hydrogen or a helium dominated universe from Big
Bang Nucleosynthesis. In the 4d parameter space of ,
catastrophic boundaries are reached by separately increasing each parameter
above its measured value by a factor of , respectively.
The fine-tuning problem of the weak scale in the Standard Model is solved: as
is increased beyond the observed value, it is impossible to maintain a
significant cosmological hydrogen abundance for any values of that
yield both hydrogen and heavy nuclei stability.
For very large values of a new regime is entered where weak interactions
freeze out before the QCD phase transition. The helium abundance becomes
independent of and is determined by the cosmic baryon and lepton
asymmetries. To maintain our explanation of from the anthropic cost of
helium dominance then requires universes with such large to be rare in the
multiverse. Implications of this are explored, including the possibility that
new physics below 10 TeV cuts off the fine-tuning in .Comment: 26 pages plus appendix, 13 figure
Coming full circle - building a sustainable community of mothers
The unexpected experience of social isolation and loneliness for new mothers is a growing issue in caring for postnatal women in the UK. Inadequate support as a result of fragmented communities and extended family can leave women at risk of poor mental health with a lasting impact the woman and her family.
Mums Circle is a student innovation in midwifery practice which promotes woman-centredness by enabling new mothers to meet, make friends and build a sustainable network of support in their local area. A year on, Mums Circle has had huge success and women are self-sustaining a growing, local community for themselves and their families
Saxion Cosmology for Thermalized Gravitino Dark Matter
In all supersymmetric theories, gravitinos, with mass suppressed by the
Planck scale, are an obvious candidate for dark matter; but if gravitinos ever
reached thermal equilibrium, such dark matter is apparently either too abundant
or too hot, and is excluded. However, in theories with an axion, a saxion
condensate is generated during an early era of cosmological history and its
late decay dilutes dark matter. We show that such dilution allows previously
thermalized gravitinos to account for the observed dark matter over very wide
ranges of gravitino mass, keV < < TeV, axion decay constant,
GeV < < GeV, and saxion mass, 10 MeV < < 100 TeV.
Constraints on this parameter space are studied from BBN, supersymmetry
breaking, gravitino and axino production from freeze-in and saxion decay, and
from axion production from both misalignment and parametric resonance
mechanisms. Large allowed regions of remain, but differ
for DFSZ and KSVZ theories. Superpartner production at colliders may lead to
events with displaced vertices and kinks, and may contain saxions decaying to
or a pair of Standard Model fermions. Freeze-in
may lead to a sub-dominant warm component of gravitino dark matter, and saxion
decay to axions may lead to dark radiation.Comment: 30 pages, 4 figure
Tapered, tubular polyester fabric
A tapered tubular polyester sleeve is described to serve as the flexible foundation for a spacesuit limb covering. The tube has a large end and a small end with a length to be determined. The ratio of taper is also determined by scale factors. All the warp yarns extend to the large end. A requisite number of warp yarns extend the full length of the sleeve. Other warp yarns extend from the large end but are terminated along the length of the sleeve. It is then woven with a filling yarn which extends in a full circle along the full length of the sleeve to thereby define the tapered sleeve. The sleeve after fabrication is then placed on a mandrel, heated in an oven, and then attached to the arm or other limb of the spacesuit
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