7,346 research outputs found
The Potential Applications of Nanoporous Materials for the Adsorption, Separation, and Catalytic Conversion of Carbon Dioxide
Sustainable CO2 adsorbents prepared by coating chitosan onto mesoporous silicas for large-scale carbon capture technology
In this article, we report a new sustainable synthesis procedure for manufacturing chitosan/silica CO2 adsorbents. Chitosan is a naturally abundant material and contains amine functionality, which is essential for selective CO2 adsorptions. It is, therefore, ideally suited for manufacturing CO2 adsorbents on a large scale. By coating chitosan onto high-surface-area mesoporous silica supports, including commercial fumed silica (an economical and accessible reagent) and synthetic SBA-15 and MCF silicas, we have prepared a new family of CO2 adsorbents, which have been fully characterised with nitrogen adsorption isotherms, thermogravimetric analysis/differential scanning calorimetry, TEM, FTIR spectroscopy and Raman spectroscopy. These adsorbents have achieved a significant CO2 adsorption capacity of up to 0.98 mmol g−1 at ambient conditions (P=1 atm and T=25 °C). The materials can also be fully regenerated/recycled on demand at temperatures as low as 75 °C with a >85 % retention of the adsorption capacity after 4 cycles, which makes them promising candidates for advanced CO2 capture, storage and utilisation technology
Thermally regenerable carbon dioxide absorbent system Final report, 1 May 1964 - 31 Jan. 1966
Carbon dioxide absorption by solid state ion exchange resin
Electron generation of leptons and hadrons with reciprocal alpha-quantized lifetimes and masses
Hadron elementary particle measurements have long revealed an
alpha-dependence in the long-lived threshold-state lifetimes, together with an
alpha-related mass structure, where alpha ~ 1/137 is the fine structure
constant. A detailed lifetime analysis shows that of the 156 particles with
well-determined lifetimes, the 120 shortest lifetimes have a continuum of
values, but the 36 longer lifetimes occur in alpha-spaced groups which are
sorted into s, c, b quark flavors. Guided by these lifetime results, we deduce
an alpha-generated set of universal mass quanta, based on the electron ground
state, which apply to both leptons and hadrons. A low-mass "threshold-state
octet" of particles - muon, proton, tau, pion, eta, eta prime, kaon, phi meson
- is reproduced to an average mass accuracy of 0.4%, with no adjustable
parameters except a small hadronic binding energy. Without the lepton states,
the hadron mass pattern is difficult to ascertain.Comment: 106 pages, 33 figures, invited review articl
Nucleosynthesis and the variation of fundamental couplings
We determine the influence of a variation of the fundamental ``constants'' on
the predicted helium abundance in Big Bang Nucleosynthesis. The analytic
estimate is performed in two parts: the first step determines the dependence of
the helium abundance on the nuclear physics parameters, while the second step
relates those parameters to the fundamental couplings of particle physics. This
procedure can incorporate in a flexible way the time variation of several
couplings within a grand unified theory while keeping the nuclear physics
computation separate from any model-dependent assumptions.Comment: 8 pages, no figure
Spectral statistics for unitary transfer matrices of binary graphs
Quantum graphs have recently been introduced as model systems to study the
spectral statistics of linear wave problems with chaotic classical limits. It
is proposed here to generalise this approach by considering arbitrary, directed
graphs with unitary transfer matrices. An exponentially increasing contribution
to the form factor is identified when performing a diagonal summation over
periodic orbit degeneracy classes. A special class of graphs, so-called binary
graphs, is studied in more detail. For these, the conditions for periodic orbit
pairs to be correlated (including correlations due to the unitarity of the
transfer matrix) can be given explicitly. Using combinatorial techniques it is
possible to perform the summation over correlated periodic orbit pair
contributions to the form factor for some low--dimensional cases. Gradual
convergence towards random matrix results is observed when increasing the
number of vertices of the binary graphs.Comment: 18 pages, 8 figure
Experimental Quantum Cryptography with Qutrits
We produce two identical keys using, for the first time, entangled trinary
quantum systems (qutrits) for quantum key distribution. The advantage of
qutrits over the normally used binary quantum systems is an increased coding
density and a higher security margin. The qutrits are encoded into the orbital
angular momentum of photons, namely Laguerre-Gaussian modes with azimuthal
index l +1, 0 and -1, respectively. The orbital angular momentum is controlled
with phase holograms. In an Ekert-type protocol the violation of a
three-dimensional Bell inequality verifies the security of the generated keys.
A key is obtained with a qutrit error rate of approximately 10 %.Comment: New version includes additional references and a few minor changes to
the manuscrip
Classification of Invariant Star Products up to Equivariant Morita Equivalence on Symplectic Manifolds
In this paper we investigate equivariant Morita theory for algebras with
momentum maps and compute the equivariant Picard groupoid in terms of the
Picard groupoid explicitly. We consider three types of Morita theory:
ring-theoretic equivalence, *-equivalence and strong equivalence. Then we apply
these general considerations to star product algebras over symplectic manifolds
with a Lie algebra symmetry. We obtain the full classification up to
equivariant Morita equivalence.Comment: 28 pages. Minor update, fixed typos
A Fast and Compact Quantum Random Number Generator
We present the realization of a physical quantum random number generator
based on the process of splitting a beam of photons on a beam splitter, a
quantum mechanical source of true randomness. By utilizing either a beam
splitter or a polarizing beam splitter, single photon detectors and high speed
electronics the presented devices are capable of generating a binary random
signal with an autocorrelation time of 11.8 ns and a continuous stream of
random numbers at a rate of 1 Mbit/s. The randomness of the generated signals
and numbers is shown by running a series of tests upon data samples. The
devices described in this paper are built into compact housings and are simple
to operate.Comment: 23 pages, 6 Figs. To appear in Rev. Sci. Inst
Are there approximate relations among transverse momentum dependent distribution functions?
Certain exact relations among transverse momentum dependent parton
distribution functions due to QCD equations of motion turn into approximate
ones upon the neglect of pure twist-3 terms. On the basis of available data
from HERMES we test the practical usefulness of one such
``Wandzura-Wilczek-type approximation'', namely of that connecting
h_{1L}^{\perp(1)a}(x) to h_L^a(x), and discuss how it can be further tested by
future CLAS and COMPASS data.Comment: 9 pages, 3 figure
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