10,500 research outputs found
Radiation protection guidelines for space missions
NASA's current radiation protection guidelines date from 1970, when the career limit was set at 400 rem. Today, using the same approach, but with the current risk estimates, a considerably lower career limit would obtain. Also, there is considerably more information about the radiation environments to be experienced in different missions than previously. Since 1970 women have joined the ranks. For these and other reasons it was necessary to reexamine the radiation protection guidelines. This task was undertaken by the National Council on Radiation Protection and Measurements Scientific Committee 75 (NCRP SC 75). Below the magnetosphere the radiation environment varies with altitude and orbit inclination. In outer space missions galactic cosmic rays, with the small but important heavy ion component, determine the radiation environment. The new recommendations for career dose limits, based on lifetime excess risk of cancer mortality, take into account age at first exposure and sex. The career limits range from 100 rem (4.0Sv) for a 24 year old female to 400 rem for a 55 year old male compared to the previous single limit of 400 rem (4.0 Sv). The career limit for the lens of the eye was reduced from 600 to 400 rem (6.0 to 4.0 Sv.
Foot-operated cell-counter
Cell-counter for cell indices consists of a footboard with four pressure sensitive switches and an enclosure for the components and circuitry. This device increases the operators efficiency by reducing the number of required hand movements
QED in strong, finite-flux magnetic fields
Lower bounds are placed on the fermionic determinants of Euclidean quantum
electrodynamics in two and four dimensions in the presence of a smooth,
finite-flux, static, unidirectional magnetic field , where
or , and is a point in the xy-plane.Comment: 10 pages, postscript (in uuencoded compressed tar file
Multiple zero modes of the Dirac operator in three dimensions
One of the key properties of Dirac operators is the possibility of a
degeneracy of zero modes. For the Abelian Dirac operator in three dimensions
the construction of multiple zero modes has been sucessfully carried out only
very recently. Here we generalise these results by discussing a much wider
class of Dirac operators together with their zero modes. Further we show that
those Dirac operators that do admit zero modes may be related to Hopf maps,
where the Hopf index is related to the number of zero modes in a simple way.Comment: Latex file, 20 pages, no figure
Evaluation of New Zoysiagrass Experimental Lines for Winter Hardiness and Turf Quality in the Transition Zone
A total of 881 zoysiagrass progeny originating from parental crosses at Texas A&M AgriLife Research – Dallas were planted in 2012, and an additional 104 progeny were planted by Kansas State University researchers in 2013. Starting in 2013, grasses were rated visually on 10 occasions through 2014. These ratings occurred throughout the year to evaluate winter survival and six turf quality characteristics to identify those progeny best adapted to the Kansas site. In September 2014, the top 20 of the original 985 progeny were selected and returned to Texas A&M AgriLife Research, Dallas, Texas, for propagation
Large-scale structure and the redshift-distance relation
In efforts to demonstrate the linear Hubble law v = Hr from galaxy
observations, the underlying simplicity is often obscured by complexities
arising from magnitude-limited data. In this paper we point out a simple but
previously unremarked fact: that the shapes and orientations of structures in
redshift space contain in themselves independent information about the
cosmological redshift-distance relation.
The orientations of voids in the CfA slice support the Hubble law, giving a
redshift-distance power index p = 0.83 +/- 0.36 (void data from Slezak, de
Lapparent, & Bijoui 1993) or p = 0.99 +/- 0.38 (void data from Malik &
Subramanian 1997).Comment: 11 pages (AASTeX), 4 figures, to appear in the Astrophysical Journal
Letter
Catching Up or Latecomer Advantage? Lessons from e-Research Strategies in Germany, in the UK and Beyond
This paper will discuss the e-Research strategies in Germany, the UK and elsewhere with a view to identifying potential lessons that can be learned. The UK e-Science initiative has been ongoing for more than five years, as has the cyberinfrastructure initiative in the US. The German D-Grid and other e-Research initiatives are much more recent. Generic lessons identified from our cross-national observations include the need to take usability into consideration at the outset of programmes; ‘soft infrastructure’ issues, such as legal and ethical considerations, can delay technological developments; ‘Grid-based infrastructure’ can seem irrelevant to domains outside of large-scale research, complex security systems often lead to ‘work-arounds’ that undermine the integrity of the system; and uptake beyond the initial development group is highly uncertain
Skewness as a probe of non-Gaussian initial conditions
We compute the skewness of the matter distribution arising from non-linear
evolution and from non-Gaussian initial perturbations. We apply our result to a
very generic class of models with non-Gaussian initial conditions and we
estimate analytically the ratio between the skewness due to non-linear
clustering and the part due to the intrinsic non-Gaussianity of the models. We
finally extend our estimates to higher moments.Comment: 5 pages, 2 ps-figs., accepted for publication in PRD, rapid com
Constraints on Galaxy Bias, Matter Density, and Primordial Non--Gausianity from the PSCz Galaxy Redshift Survey
We compute the bispectrum for the \IRAS PSCz catalog and find that the galaxy
distribution displays the characteristic signature of gravity. Assuming
Gaussian initial conditions, we obtain galaxy biasing parameters
and , with no sign of
scale-dependent bias for h/Mpc. These results impose stringent
constraints on non-Gaussian initial conditions. For dimensional scaling models
with statistics, we find N>49, which implies a constraint on
primordial skewness .Comment: 4 pages, 3 embedded figures, uses revtex style file, minor changes to
reflect published versio
Evaluation of Colorants on ‘Sharpshooter’ and ‘Cody’ Buffalograss
Turf colorants effectively enhanced green color of dormant buffalograss. Using a higher application rate or adding a midwinter application helped longevity of color. Colorants increased canopy temperatures more consistently than soil temperatures, which may encourage earlier spring greenup
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