8,368 research outputs found
A thermodynamic basis for prebiotic amino acid synthesis and the nature of the first genetic code
Of the twenty amino acids used in proteins, ten were formed in Miller's
atmospheric discharge experiments. The two other major proposed sources of
prebiotic amino acid synthesis include formation in hydrothermal vents and
delivery to Earth via meteorites. We combine observational and experimental
data of amino acid frequencies formed by these diverse mechanisms and show
that, regardless of the source, these ten early amino acids can be ranked in
order of decreasing abundance in prebiotic contexts. This order can be
predicted by thermodynamics. The relative abundances of the early amino acids
were most likely reflected in the composition of the first proteins at the time
the genetic code originated. The remaining amino acids were incorporated into
proteins after pathways for their biochemical synthesis evolved. This is
consistent with theories of the evolution of the genetic code by stepwise
addition of new amino acids. These are hints that key aspects of early
biochemistry may be universal.Comment: 16 pages, 2 tables, 4 figures. Accepted for publication in
Astrobiolog
Development and fabrication of radiation resistant high efficiency solar cells Final periodic report, 24 Aug. 1966 - 24 Feb. 1967
Diffusion process for lithium doping of solar cells, and electrical characteristics and radiation resistance of solar cell
Management of plant health risks associated with processing of plant-based wastes: A review
The rise in international trade of plants and plant products has increased the risk of introduction and spread of plant pathogens and pests. In addition, new risks are arising from the implementation of more environmentally friendly methods of biodegradable waste disposal, such as composting and anaerobic digestion. As these disposal methods do not involve sterilisation, there is good evidence that certain plant pathogens and pests can survive these processes. The temperature/time profile of the disposal process is the most significant and easily defined factor in controlling plant pathogens and pests. In this review, the current evidence for temperature/time effects on plant pathogens and pests is summarised. The advantages and disadvantages of direct and indirect process validation for the verification of composting processes, to determine their efficacy in destroying plant pathogens and pests in biowaste, are discussed. The availability of detection technology and its appropriateness for assessing the survival of quarantine organisms is also reviewed
High temperature cyclic oxidation data. Part 1: Turbine alloys
Specific-weight-change-versus-time data and x ray diffraction results are presented derived from high temperature cyclic tests on high temperature, high strength nickel-base gamma/gamma prime and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample
Coherent analysis of quantum optical sideband modes
We demonstrate a device that allows for the coherent analysis of a pair of
optical frequency sidebands in an arbitrary basis. We show that our device is
quantum noise limited and hence applications for this scheme may be found in
discrete and continuous variable optical quantum information experiments.Comment: 3 pages, 3 figures, submitted to Optics Letter
Getting just the Supersymmetric Standard Model at Intersecting Branes on the Z6-orientifold
In this paper, globally N=1 supersymmetric configurations of intersecting
D6-branes on the Z6-orientifold are discussed, involving also fractional
branes. It turns out rather miraculously that one is led almost automatically
to just ONE particular class of 5 stack models containing the SM gauge group,
which all have the same chiral spectrum. The further discussion shows that
these models can be understood as exactly the supersymmetric standard model
without any exotic chiral symmetric/antisymmetric matter. The superpartner of
the Higgs finds a natural explanation and the hypercharge remains massless.
However, the non-chiral spectrum within the model class is very different and
does not in all cases allow for a N=2 low energy field theoretical
understanding of the necessary breaking U(1)xU(1)->U(1) along the Higgs branch,
which is needed in order to get the standard Yukawa couplings. Also the
left-right symmetric models belong to exactly one class of chiral spectra,
where the two kinds of exotic chiral fields can have the interpretation of
forming a composite Higgs. The aesthetical beauty of these models, involving
only non-vanishing intersection numbers of an absolute value three, seems to be
unescapable.Comment: 45 pages, 2 figures, v3:some signs corrected in erratum, conclusions
unchange
Grower-processor agreements in the sweet corn for processing industry in the North Central states
Linear Optical CNOT Gate in the Coincidence Basis
We describe the operation and tolerances of a non-deterministic, coincidence
basis, quantum CNOT gate for photonic qubits. It is constructed solely from
linear optical elements and requires only a two-photon source for its
demonstration.Comment: Submitted to Physical Review
Multiplexed communication over a high-speed quantum channel
In quantum information systems it is of particular interest to consider the
best way in which to use the non-classical resources consumed by that system.
Quantum communication protocols are integral to quantum information systems and
are amongst the most promising near-term applications of quantum information
science. Here we show that a multiplexed, digital quantum communications system
supported by comb of vacuum squeezing has a greater channel capacity per photon
than a source of broadband squeezing with the same analogue bandwidth. We
report on the time-resolved, simultaneous observation of the first dozen teeth
in a 2.4 GHz comb of vacuum squeezing produced by a sub-threshold OPO, as
required for such a quantum communications channel. We also demonstrate
multiplexed communication on that channel
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