1,518 research outputs found
Nuclear Ca2+ signalling in arbuscular mycorrhizal and actinorhizal endosymbioses: on the trail of novel underground signals
Root endosymbioses are beneficial associations formed between terrestrial plants and either bacterial or fungal micro-organisms. A common feature of these intracellular symbioses is the requirement for mutual recognition between the two partners before host-regulated microbial entry. As part of this molecular dialogue, symbiosis-specific microbial factors set in motion a highly conserved plant signal transduction pathway, of which a central component is the activation of sustained nuclear Ca2+ oscillations in target cells of the host epidermis. Here, we focus on recent findings concerning this crucial Ca2+-dependent signalling step for endosymbiotic associations involving either arbuscular mycorrhizal fungi or nitrogen-fixing Frankia actinomycetes, and in particular how this knowledge is contributing to the identification of the respective microbial factors
Using LDGM Codes and Sparse Syndromes to Achieve Digital Signatures
In this paper, we address the problem of achieving efficient code-based
digital signatures with small public keys. The solution we propose exploits
sparse syndromes and randomly designed low-density generator matrix codes.
Based on our evaluations, the proposed scheme is able to outperform existing
solutions, permitting to achieve considerable security levels with very small
public keys.Comment: 16 pages. The final publication is available at springerlink.co
Weighted complex projective 2-designs from bases: optimal state determination by orthogonal measurements
We introduce the problem of constructing weighted complex projective
2-designs from the union of a family of orthonormal bases. If the weight
remains constant across elements of the same basis, then such designs can be
interpreted as generalizations of complete sets of mutually unbiased bases,
being equivalent whenever the design is composed of d+1 bases in dimension d.
We show that, for the purpose of quantum state determination, these designs
specify an optimal collection of orthogonal measurements. Using highly
nonlinear functions on abelian groups, we construct explicit examples from d+2
orthonormal bases whenever d+1 is a prime power, covering dimensions d=6, 10,
and 12, for example, where no complete sets of mutually unbiased bases have
thus far been found.Comment: 28 pages, to appear in J. Math. Phy
Amplitude analysis of reactions pi(-)p->etapi(-)p and pi(-)p->etapi(0)n on polarized target and the exotic 1-+ meson
Recently several experimental groups analysed data on and reactions with exotic -wave and
found a conflicting evidence for an exotic meson . High
statistics data on these reactions are presently analysed by BNL E852
Collaboration. All these analyses are based on the crucial assumption that the
production amplitudes do not depend on nucleon spin. This assumption is in
sharp conflict with the results of measurements of ,
and on polarized targets at
CERN which find a strong dependence of production amplitudes on nucleon spin.
To ascertain the existence of exotic meson , it is necessary to
perform a model-independent amplitude analysis of reactions and . We demonstrate that measurements of
these reactions on transversely polarized targets enable the required model
independent amplitude analysis without the assumption that production
amplitudes are independent on nucleon spin. We suggest that high statistics
measurements of reactions and be made on polarized targets at BNL and at Protvino IHEP, and that
model-independent amplitude analyses of this polarized data be performed to
advance hadron spectroscopy on the level of spin dependent production
amplitudes.Comment: 23 page
Continuous-variable sampling from photon-added or photon-subtracted squeezed states
We introduce a new family of quantum circuits in Continuous Variables and we
show that, relying on the widely accepted conjecture that the polynomial
hierarchy of complexity classes does not collapse, their output probability
distribution cannot be efficiently simulated by a classical computer. These
circuits are composed of input photon-subtracted (or photon-added) squeezed
states, passive linear optics evolution, and eight-port homodyne detection. We
address the proof of hardness for the exact probability distribution of these
quantum circuits by exploiting mappings onto different architectures of
sub-universal quantum computers. We obtain both a worst-case and an
average-case hardness result. Hardness of Boson Sampling with eight-port
homodyne detection is obtained as the zero squeezing limit of our model. We
conclude with a discussion on the relevance and interest of the present model
in connection to experimental applications and classical simulations.Comment: 11 pages, 6 figure
Transitions and Probes in Turbulent Helium
Previous analysis of a Paris turbulence experiment \cite{zoc94,tab95} shows a
transition at the Taylor Reynolds number \rel \approx 700. Here correlation
function data is analyzed which gives further evidence for this transition. It
is seen in both the power spectrum and in structure function measurements. Two
possible explanations may be offered for this observed transition: that it is
intrinsic to the turbulence flow in this closed box experiment or that it is an
effect of a change in the flow around the anemometer. We particularly examine a
pair of ``probe effects''. The first is a thermal boundary layer which does
exist about the probe and does limit the probe response, particularly at high
frequencies. Arguments based on simulations of the response and upon
observations of dissipation suggests that this effect is only crucial beyond
\rel\approx 2000. The second effect is produced by vortex shedding behind the
probe. This has been seen to produce a large modification in some of the power
spectra for large \rel. It might also complicate the interpretation of the
experimental results. However, there seems to be a remaining range of data for
\rel < 1300 uncomplicated by these effects, and which are thus suggestive of
an intrinsic transition.Comment: uuencoded .ps files. submitted to PRE. 12 figures are sent upon
request to jane wang ([email protected]
A role for the mevalonate pathway in early plant symbiotic signaling
Rhizobia and arbuscular mycorrhizal fungi produce signals that are perceived by host legume receptors at the plasma membrane and trigger sustained oscillations of the nuclear and perinuclear Ca(2+) concentration (Ca(2+) spiking), which in turn leads to gene expression and downstream symbiotic responses. The activation of Ca(2+) spiking requires the plasma membrane-localized receptor-like kinase Does not Make Infections 2 (DMI2) as well as the nuclear cation channel DMI1. A key enzyme regulating the mevalonate (MVA) pathway, 3-Hydroxy-3-Methylglutaryl CoA Reductase 1 (HMGR1), interacts with DMI2 and is required for the legume-rhizobium symbiosis. Here, we show that HMGR1 is required to initiate Ca(2+) spiking and symbiotic gene expression in Medicago truncatula roots in response to rhizobial and arbuscular mycorrhizal fungal signals. Furthermore, MVA, the direct product of HMGR1 activity, is sufficient to induce nuclear-associated Ca(2+) spiking and symbiotic gene expression in both wild-type plants and dmi2 mutants, but interestingly not in dmi1 mutants. Finally, MVA induced Ca(2+) spiking in Human Embryonic Kidney 293 cells expressing DMI1. This demonstrates that the nuclear cation channel DMI1 is sufficient to support MVA-induced Ca(2+) spiking in this heterologous system
- …