20,278 research outputs found
Water management subsystem specification for space flights of extended time periods. Life support system for space flights of extended time periods
Water management subsystem of life support system for manned space flight specification
Ternary inorganic compounds containing carbon, nitrogen, and oxygen at high pressures
Ternary C_{x}N_{y}O_{z} compounds are actively researched as novel high
energy density and ultrahard materials. Although some synthesis work has been
performed at ambient conditions, very little is known about the high pressure
chemistry of of C_{x}N_{y}O_{z} compounds. In this work, first principles
variable-composition evolutionary structure prediction calculations are
performed with the goal of discovering novel mixed C_{x}N_{y}O_{z} materials at
ambient and high pressure conditions. By systematically searching ternary
variable composition crystalline materials, the full ternary phase diagram is
constructed in the range of pressures from 0 to 100 GPa. The search finds the
C_{2}N_{2}O crystal containing extended covalent network of C, N, and O atoms,
having space group symmetry Cmc2_{1}, and stable above just 10 GPa. Several
other novel metastable (CO)_{x}-(N)_{y} crystalline compounds discovered during
the search, including two polymorphs of C_{2}NO_{2} and two polymorphs of
C_{3}N_{2}O_{3} crystals are found to be energetically favorable compared to
polymeric carbon monoxide (CO) and nitrogen. Predicted new compounds are
characterized by their Raman spectra and equations of state
A study of A8 and A2 migrants in Nottingham
The research was commissioned by Nottingham City Council and One Nottingham in August 2008 and was conducted by a team of researchers from the Salford Housing & Urban Studies Unit at the University of Salford. The study was greatly aided by research support from Nottingham City Council Children’s Services Asylum Seeker/Refugee Support Team, as well as a number of community interviewers. The project was managed by a steering group composed of officers representing Nottingham City Council, One Nottingham, Nottingham City Homes, NHS Nottingham City, Nottinghamshire Fire & Rescue Service, Nottinghamshire Police and Basic Educational Guidance in Nottinghamshire (BEGIN). The main objective of this research was to explore the needs and experiences of A8 and A2 migrants living and working in Nottingham
Novel Potassium Polynitrides at High Pressures
Polynitrogen compounds have attracted great interest due to their potential
applications as high energy density materials. Most recently, a rich variety of
alkali polynitrogens (R_{x}N_{y}; R=Li, Na, and Cs) have been predicted to be
stable at high pressures and one of them, CsN_{5} has been recently
synthesized. In this work, various potassium polynitrides are investigated
using first-principles crystal structure search methods. Several novel
molecular crystals consisting of N_{4} chains, N_{5} rings, and N_{6} rings
stable at high pressures are discovered. In addition, an unusual nitrogen-rich
metallic crystal with stoichiometry K_{2}N_{16} consisting of a planar
two-dimensional extended network of nitrogen atoms arranged in fused eighteen
atom rings is found to be stable above 70 GPa. An appreciable electron transfer
from K to N atoms is responsible for the appearance of unexpected chemical
bonding in these crystals. The thermodynamic stability and high pressure phase
diagram is constructed. The electronic and vibrational properties of the
layered polynitrogen K_{2}N_{16} compound are investigated, and the
pressure-dependent IR-spectrum is obtained to assist in experimental discovery
of this new high-nitrogen content material
PPl 15: The First Brown Dwarf Spectroscopic Binary
PPl 15 is the first object to have been confirmed as a brown dwarf by the
lithium test (in 1995), though its inferred mass was very close to the
substellar limit. It is a member of the Pleiades open cluster. Its position in
a cluster color-magnitude diagram suggested that it might be binary, and
preliminary indications that it is a double-lined spectroscopic binary were
reported by us in 1997. Here we report on the results of a consecutive week of
Keck HIRES observations of this system, which yield its orbit. It has a period
of about 5.8 days, and an eccentricity of 0.4+/-0.05. The rotation of the stars
is slow for this class of objects. Because the system luminosity is divided
between 2 objects with a mass ratio of 0.85, this renders each of them an
incontrovertible brown dwarf, with masses between 60-70 jupiters. We show that
component B is a little redder than A by studying their wavelength-dependent
line ratios, and that this variation is compatible with the mass ratio. We
confirm that the system has lithium, but cannot support the original conclusion
that it is depleted (which would be surprising, given the new masses). This is
a system of very close objects which, if they had combined, would have produced
a low mass star. We discuss the implications of this discovery for the theories
of binary formation and formation of very low mass objects.Comment: Latex, 18 pages, 4 figures, submitted to Astron.
Pentazole and Ammonium Pentazolate: Crystalline Hydro-Nitrogens at High Pressure
Two new crystalline compounds, pentazole (N_{5}H) and ammonium pentazolate
(NH_{4})(N_{5}), both featuring cyclo-{\rm N_{5}^{-}} are discovered using
first principles evolutionary search of the nitrogen-rich portion of the
hydro-nitrogen binary phase diagram (N_{x}H_{y}, x\geqy) at high pressures.
Both crystals consist of the pentazolate N_{5}^{-} anion and ammonium
NH_{4}^{+} or hydrogen H^{+} cations. These two crystals are predicted to be
thermodynamically stable at pressures above 30 GPa for (NH_{4})(N_{5}) and 50
GPa for pentazole N_{5}H. The chemical transformation of ammonium azide
(NH_{4})(N_{3}) mixed with di-nitrogen (N_{2}) to ammonium pentazolate
(NH_{4})(N_{5}) is predicted to become energetically favorable above 12.5 GPa.
To assist in identification of newly synthesized compounds in future
experiments, the Raman spectra of both crystals are calculated and mode
assignments are made as a function of pressure up to 75 GPa
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