325 research outputs found
Distributed Discontinuous Coupling for Convergence in Heterogeneous Networks
In this letter, we propose the use of a distributed discontinuous coupling protocol to achieve convergence and synchronization in networks of non-identical nonlinear dynamical systems. We show that the synchronous dynamics is a solution to the average of the nodes' vector fields, and derive analytical estimates of the critical coupling gains required to achieve convergence
Efficiency of transient transformation in tobacco protoplasts is independent of plasmid amount
An optimized protocol for the
transient transformation of tobacco protoplasts mediated
by polyethylene\u2013glycol (PEG) is here described. As expected, the quantitative
b\u2013glucuronidase (Gus) activity driven by pCaMVGus
was dependent on the amount of plasmid used.
Nevertheless, we demonstrate by an immunodetection
method that transformation efficiency did not depend on
the amount of plasmid used but on the limitation imposed
by cell competence. In fact, we obtained the same
percentage of transformed cells (about 60%) using a wide
range of plasmid concentrations (0.1\u201310 mg per test).
Finally, we show that, when we used two plasmid types in
a mixture at a concentration ranging from 0.1 to 10 mg for
each, all transformed cells expressed proteins encoded by
both plasmids. Transient expression and co-transformation
experiments are routinely used methods and, probably,
the major results from this work were assumed by
many researchers in this field, but our data experimentally
support this assumption
Similarity of nuclear structure in 132Sn and 208Pb regions: proton-neutron multiplets
Starting from the striking similarity of proton-neutron multiplets in 134Sb
and 210Bi, we perform a shell-model study of nuclei with two additional protons
or neutrons to find out to what extent this analogy persists. We employ
effective interactions derived from the CD-Bonn nucleon-nucleon potential
renormalized by use of the V-low-k approach. The calculated results for 136Sb,
212Bi, 136I, and 212At are in very good agreement with the available
experimental data. The similarity between 132Sn and 208Pb regions is discussed
in connection with the effective interaction, emphasizing the role of core
polarization effects.Comment: 4 pages, 3 figures, 2 table
The product of the rice myb7 unspliced mRNA dimerizes with the maize leucine-zipper opaque2 and stimulates its activity in transient expression assay
myb7 mRNA is present in rice in spliced and unspliced forms, splicing being enhanced by anoxia. The protein (Mybleu) encoded by the unspliced mRNA is composed of an incomplete Myb domain followed by a leucine zipper; however, it lacks canonical sequences for DNA binding, transcriptional activation, and nuclear localization. We show here that in transiently transformed tobacco protoplasts, Mybleu is able to enhance the transcriptional activity of the maize leucine zipper Opaque2 on its target b32 promoter. The Mybleu transactivation effect is strictly dependent on the presence of Opaque2 and is driven by Mybleu-Opaque2 heterodimers. Mybleu is located in the nucleus, both in rice and in transformed tobacco protoplasts. In rice, the protein is expressed in regions corresponding to undifferentiated cells of roots and coleoptiles. Therefore, myb7 mRNA encodes, depending on its splicing, two transcription factors belonging to separate classes. One of them, Myblue, has novel structural characteristics, suggesting the existence of new mechanisms acting in the activation of transcription.
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Proton-Neutron Interaction near Closed Shells
Odd-odd nuclei around double shell closures are a direct source of
information on the proton-neutron interaction between valence nucleons. We have
performed shell-model calculations for doubly odd nuclei close to Pb,
Sn and Sn using realistic effective interactions derived from
the CD-Bonn nucleon-nucleon potential. The calculated results are compared with
the available experimental data, attention being focused on particle-hole and
particle-particle multiplets. While a good agreement is obtained for all the
nuclei considered, a detailed analysis of the matrix elements of the effective
interaction shows that a stronger core-polarization contribution seems to be
needed in the particle-particle case.Comment: 8 pages, 6 figures, Proccedings of the International Conference
"Nuclear Structure and Related Topics", Dubna, Russia, September 2-6, 2003,
to be published in Yadernaia Fizika (Physics of Atomic Nuclei
Realistic Shell-Model Calculations for Proton-Rich N=50 Isotones
The structure of the N=50 isotones 98Cd, 97Ag, and 96Pd is studied in terms
of shell model employing a realistic effective interaction derived from the
Bonn-A nucleon-nucleon potential. The single-hole energies are fixed by
resorting to an analysis of the low-energy spectra of the isotones with A>= 91.
Comparison shows that our results are in very satisfactory agreement with the
available experimental data. This supports confidence in the predictions of our
calculationsComment: 8 pages, 3 figures, to be published on Journal of Physics
Realistic shell-model calculations for proton particle-neutron hole nuclei around 132Sn
We have performed shell-model calculations for nuclei with proton particles
and neutron holes around 132Sn using a realistic effective interaction derived
from the CD-Bonn nucleon-nucleon potential. For the proton-neutron channel this
is explicitly done in the particle-hole formalism. The calculated results are
compared with the available experimental data, particular attention being
focused on the proton particle-neutron hole multiplets. A very good agreement
is obtained for all the four nuclei considered, 132Sb, 130Sb, 133Te and 131Sb.
We predict many low-energy states which have no experimental counterpart. This
may stimulate, and be helpful to, future experiments.Comment: 8 pages, 6 figures, to be published on Physical Review
Overexpression of Osmyb4 enhances compatible solute accumulation and increases stress tolerance of arabidopsis thaliana
In this paper, we report the metabolic and molecular changes in response to cold and drought induced in Osmyb4 transgenic Arabidopsis thaliana compared with the wildtype (WT). The rice Osmyb4 gene codes for a transcription factor (Myb4) induced by cold treatment and, in Arabidopsis transgenic plants, improves cold and freezing tolerance [Vannini C, Locatelli F, Bracale M, Magnani E, Marsoni M, Osnato M, Mattana M, Baldoni E, Coraggio I (2004) Plant J 37: 115-127]. Here, we report the ability of Myb4 to induce also drought tolerance in Arabidopsis transgenic plants. By the use of nuclear magnetic resonance (NMR) and enzymatic assays, we showed that several compatible solutes (glucose, fructose, sucrose, proline, glycine betaine and sinapoyl malate) accumulate in higher amount in Osmyb4-overexpressing plants with respect to the WT, both under normal and stress conditions. Considering proline, we also found that in transgenic plants the levels of the mRNAs coding for \u3941- pyrroline-5-carboxylate synthase (EC not assigned) and for \u3941- pyrroline-5-carboxylate dehydrogenase (EC 1.5.1.12) were higher and lower, respectively. The constitutive activation of several stress-inducible pathways and different kinetics in the accumulation of several metabolites, in Myb4 transgenic plants, may represent an advantage to prepare plants to face the stress condition. Moreover, these results taken together suggest that Myb4 integrates the activation of multiple components of stress response
Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces
A recent calculation of the nuclear energy density functional from chiral
two- and three-nucleon forces is extended to the isovector terms pertaining to
different proton and neutron densities. An improved density-matrix expansion is
adapted to the situation of small isospin-asymmetries and used to calculate in
the Hartree-Fock approximation the density-dependent strength functions
associated with the isovector terms. The two-body interaction comprises of
long-range multi-pion exchange contributions and a set of contact terms
contributing up to fourth power in momenta. In addition, the leading order
chiral three-nucleon interaction is employed with its parameters fixed in
computations of nuclear few-body systems. With this input one finds for the
asymmetry energy of nuclear matter the value MeV,
compatible with existing semi-empirical determinations. The strength functions
of the isovector surface and spin-orbit coupling terms come out much smaller
than those of the analogous isoscalar coupling terms and in the relevant
density range one finds agreement with phenomenological Skyrme forces. The
specific isospin- and density-dependences arising from the chiral two- and
three-nucleon interactions can be explored and tested in neutron-rich systems.Comment: 14 pages, 7 figures, to be published in European Physical Journal
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