9,099 research outputs found
Dileptons in a coarse-grained transport approach
We calculate dilepton spectra in heavy-ion collisions using a coarse-graining
approach to the simulation of the created medium with the UrQMD transport
model. This enables the use of dilepton-production rates evaluated in
equilibrium quantum-field theory at finite temperatures and chemical
potentials.Comment: 4 pages, 2 figures, contribution to the proceedings of "The 15th
International Conference on Strangeness in Quark Matter" (SQM 2015), 06-11
July in Dubna, Russi
Radio Frequency Interference /RFI/ design guide for aerospace communications systems
Radio frequency interference design guide for aerospace communications system
Gefangen im Netz: kritische Anmerkungen zum Umgang mit der Netzwerkrhetorik
Durch den inflationären Gebrauch des Begriffs «Netzwerk» stellt sich die Frage, ob etwas, an dem mehrere Akteure oder Institutionen beteiligt sind, «Kein-Netzwerk» sein kann. Weiterbildungsanbieter, Regionen - selbst unsere moderne Gesellschaft - scheinen vernetzt. Aber stimmt das Bild von innovationsfreudigen Netzwerken in der Weiterbildung, oder handelt es sich um eine rhetorisch gut positionierte Worthülse, die von den wirklichen Herausforderungen ablenkt
Canonical decomposition of linear differential operators with selected differential Galois groups
We revisit an order-six linear differential operator having a solution which
is a diagonal of a rational function of three variables. Its exterior square
has a rational solution, indicating that it has a selected differential Galois
group, and is actually homomorphic to its adjoint. We obtain the two
corresponding intertwiners giving this homomorphism to the adjoint. We show
that these intertwiners are also homomorphic to their adjoint and have a simple
decomposition, already underlined in a previous paper, in terms of order-two
self-adjoint operators. From these results, we deduce a new form of
decomposition of operators for this selected order-six linear differential
operator in terms of three order-two self-adjoint operators. We then generalize
the previous decomposition to decompositions in terms of an arbitrary number of
self-adjoint operators of the same parity order. This yields an infinite family
of linear differential operators homomorphic to their adjoint, and, thus, with
a selected differential Galois group. We show that the equivalence of such
operators is compatible with these canonical decompositions. The rational
solutions of the symmetric, or exterior, squares of these selected operators
are, noticeably, seen to depend only on the rightmost self-adjoint operator in
the decomposition. These results, and tools, are applied on operators of large
orders. For instance, it is seen that a large set of (quite massive) operators,
associated with reflexive 4-polytopes defining Calabi-Yau 3-folds, obtained
recently by P. Lairez, correspond to a particular form of the decomposition
detailed in this paper.Comment: 40 page
Site-selective protein modification via disulfide rebridging for fast tetrazine/trans-cyclooctene bioconjugation
An inverse electron demand Diels–Alder reaction between tetrazine and trans-cyclooctene (TCO) holds great promise for protein modification and manipulation. Herein, we report the design and synthesis of a tetrazine-based disulfide rebridging reagent, which allows the site-selective installation of a tetrazine group into disulfide-containing peptides and proteins such as the hormone somatostatin (SST) and the antigen binding fragment (Fab) of human immunoglobulin G (IgG). The fast and efficient conjugation of the tetrazine modified proteins with three different TCO-containing substrates to form a set of bioconjugates in a site-selective manner was successfully demonstrated for the first time. Homogeneous, well-defined bioconjugates were obtained underlining the great potential of our method for fast bioconjugation in emerging protein therapeutics. The formed bioconjugates were stable against glutathione and in serum, and they maintained their secondary structure. With this work, we broaden the scope of tetrazine chemistry for site-selective protein modification to prepare well-defined SST and Fab conjugates with preserved structures and good stability under biologically relevant conditions
Cosmological Evolution of Supergiant Star-Forming Clouds
In an exploration of the birthplaces of globular clusters, we present a
careful examination of the formation of self-gravitating gas clouds within
assembling dark matter haloes in a hierarchical cosmological model. Our
high-resolution smoothed particle hydrodynamical simulations are designed to
determine whether or not hypothesized supergiant molecular clouds (SGMCs) form
and, if they do, to determine their physical properties and mass spectra. It
was suggested in earlier work that clouds with a median mass of several 10^8
M_sun are expected to assemble during the formation of a galaxy, and that
globular clusters form within these SGMCs. Our simulations show that clouds
with the predicted properties are indeed produced as smaller clouds collide and
agglomerate within the merging dark matter haloes of our cosmological model. We
find that the mass spectrum of these clouds obeys the same power-law form
observed for globular clusters, molecular clouds, and their internal clumps in
galaxies, and predicted for the supergiant clouds in which globular clusters
may form. We follow the evolution and physical properties of gas clouds within
small dark matter haloes up to z = 1, after which prolific star formation is
expected to occur. Finally, we discuss how our results may lead to more
physically motivated "rules" for star formation in cosmological simulations of
galaxy formation.Comment: Accepted to The Astrophysical Journal; 17 pages, 8 figure
Painleve versus Fuchs
The sigma form of the Painlev{\'e} VI equation contains four arbitrary
parameters and generically the solutions can be said to be genuinely
``nonlinear'' because they do not satisfy linear differential equations of
finite order. However, when there are certain restrictions on the four
parameters there exist one parameter families of solutions which do satisfy
(Fuchsian) differential equations of finite order. We here study this phenomena
of Fuchsian solutions to the Painlev{\'e} equation with a focus on the
particular PVI equation which is satisfied by the diagonal correlation function
C(N,N) of the Ising model. We obtain Fuchsian equations of order for
C(N,N) and show that the equation for C(N,N) is equivalent to the
symmetric power of the equation for the elliptic integral .
We show that these Fuchsian equations correspond to rational algebraic curves
with an additional Riccati structure and we show that the Malmquist Hamiltonian
variables are rational functions in complete elliptic integrals. Fuchsian
equations for off diagonal correlations are given which extend our
considerations to discrete generalizations of Painlev{\'e}.Comment: 18 pages, Dedicated to the centenary of the publication of the
Painleve VI equation in the Comptes Rendus de l'Academie des Sciences de
Paris by Richard Fuchs in 190
0- quantum transition in a carbon nanotube Josephson junction: universal phase dependence and orbital degeneracy
We investigate experimentally the supercurrent in a clean carbon nanotube
quantum dot, close to orbital degeneracy, connected to superconducting leads in
a regime of strong competition between local electronic correlations and
superconducting proximity effect. For an odd occupancy of the dot and
intermediate coupling to the reservoir, the Kondo effect can develop in the
normal state and screen the local magnetic moment of the dot. This leads to
singlet-doublet transitions that strongly affect the Josephson effect in a
single-level quantum dot: the sign of the supercurrent changes from positive to
negative (0 to -junction). In the regime of strongest competition between
the Kondo effect and proximity effect, meaning that the Kondo temperature
equals the superconducting gap, the magnetic state of the dot undergoes a first
order quantum transition induced by the superconducting phase difference across
the junction. This is revealed experimentally by anharmonic current-phase
relations. In addition, the very specific electronic configuration of clean
carbon nanotubes, with two nearly orbitally degenerated states, leads to
different physics depending whether only one or both quasi-degenerate upper
levels of the dots participate to transport, which is determined by their
occupancy and relative widths. When the transport of Cooper pairs takes place
through only one of these levels, we find that the phase diagram of the
phase-dependent 0- transition is a universal characteristic of a
discontinuous level-crossing quantum transition at zero temperature. In the
case were two levels participate to transport, the nanotube Josephson current
exhibits a continuous 0- transition, independent of the superconducting
phase, revealing a different physical mechanism of the transition.Comment: 14 pages, 12 figure
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