3,589 research outputs found
The CArG Boxes in the Promoter of the Arabidopsis Floral Organ Identity Gene APETALA3 Mediate Diverse Regulatory Effects
APETALA3 is a MADS box gene required for normal development of the petals and stamens in the Arabidopsis flower. Studies in yeast, mammals and plants demonstrate that MADS domain transcription factors bind with high affinity to a consensus sequence called the CArG box. The APETALA3 promoter contains three close matches to the consensus CArG box sequence. To gain insights into the APETALA3 regulatory circuitry, we have analyzed the APETALA3 promoter using AP3::uidA(GUS) fusions. 496 base pairs of APETALA3 promoter sequence 5′ to the transcriptional start directs GUS activity in the same temporal and spatial expression pattern as the APETALA3 RNA and protein in wild-type flowers. A synthetic promoter consisting of three tandem repeats of a 143 base pair sequence directs reporter gene activity exclusively to
INTRODUCTION
The developmental fate of the organs in the Arabidopsis flower is controlled by the homeotic floral organ identity genes. When the activity of a particular floral organ identity gene is lost due to mutation, there is a homeotic conversion of one organ type to another. For example, the APETALA3 (AP3) and PISTILLATA (PI) genes are necessary for the proper development of petals that develop in the second whorl and stamens that develop in the third whorl of the flower. In ap3 and pi mutants, sepals and carpels develop in positions normally occupied by petals and stamens respectively (Bowman et al., 1989; Jack et al., 1992). Accumulating genetic and molecular evidence suggests that the AP3 and PI proteins together make up the B class organ identity function and these two proteins are sufficient to direct the identity of petals and stamens in the flower. In support of this, ectopic expression of AP3 and/or PI throughout the flower leads to homeotic transformations. Specifically misexpression of AP3 (i.e. 35S::AP3) results in the development of stamens in place of carpels in the fourth whorl and misexpression of PI (i.e. 35S::PI) results in the development of petaloid sepals in place of sepals in the first whorl of the flower (Jack et al., 1994; Krizek and Meyerowitz, 1996). 35S::AP3 leads to fourth whorl organ identity changes because PI is transiently expressed in whorl four during early stages of flower
petals and stamens in the flower. We have analyzed the role of the CArG boxes by site-specific mutagenesis and find that the three CArG boxes mediate discrete regulatory effects. Mutations in CArG1 result in a decrease in reporter expression suggesting that CArG1 is the binding site for a positively acting factor or factors. Mutations in CArG2 result in a decrease in reporter expression in petals, but the expression pattern in stamens is unchanged. By contrast, mutations in CArG3 result in an increase in the level of reporter gene activity during early floral stages suggesting that CArG3 is the binding site for a negatively acting factor
Qudits for Witnessing Quantum Gravity Induced Entanglement of Masses Under Decoherence
Recently a theoretical and an experimental protocol known as quantum gravity
induced entanglement of masses (QGEM) has been proposed to test the quantum
nature of gravity using two mesoscopic masses each placed in a superposition of
two locations. If, after eliminating all non-gravitational interactions between
them, the particles become entangled, one can conclude that the gravitational
potential is induced via a quantum mediator, i.e. a virtual graviton. In this
paper, we examine a range of different experimental set-ups, considering
different geometries and the number of spatially superposed states taken, in
order to determine which would generate entanglement faster. We conclude that
without decoherence, and given a maximum distance between any two
spatial states of a superposition, a set of two qubits placed in spatial
superposition parallel to one another will outperform all other models given
realistic experimental parameters. Furthermore, when a sufficiently high
decoherence rate is introduced, multi-component superpositions can outperform
the two-qubit set-up. This is further verified with an experimental simulation,
showing that measurements are required to reject the no entanglement
hypothesis with a parallel qubits set-up without decoherence at a 99.9
confidence level. The number of measurements increases when decoherence is
introduced. When the decoherence rate reaches ~Hz, 6-dimensional qudits
are required as the two-qubit system entanglement cannot be witnessed anymore.
However, in this case, measurements will be required. One can group
the witness operators to measure in order to reduce the number of measurements
(up to ten-fold). However, this may be challenging to implement experimentally.Comment: 15 pages, 20 figures, 2 table
Autoimmunity-related atrial fibrillation incidence:an emerging conundrum meriting further investigation: authors' reply
Equation of Motion for a Spin Vortex and Geometric Force
The Hamiltonian equation of motion is studied for a vortex occuring in
2-dimensional Heisenberg ferromagnet of anisotropic type by starting with the
effective action for the spin field formulated by the Bloch (or spin) coherent
state. The resultant equation shows the existence of a geometric force that is
analogous to the so-called Magnus force in superfluid. This specific force
plays a significant role for a quantum dynamics for a single vortex, e.g, the
determination of the bound state of the vortex trapped by a pinning force
arising from the interaction of the vortex with an impurity.Comment: 13 pages, plain te
Computation of molecular excited states on IBM quantum computers using a discriminative variational quantum eigensolver
Solving for molecular excited states remains one of the key challenges of modern quantum chemistry. Traditional methods are constrained by existing computational capabilities, limiting the complexity of the molecules that can be studied or the accuracy of the results that can be obtained. Several quantum computing methods have been suggested to address this limitation. However, these typically have hardware requirements which may not be achieved in the near term. We propose a variational quantum machine learning based method to determine molecular excited states aiming at being as resilient as possible to the defects of early noisy intermediate scale quantum computers and demonstrate an implementation for H
on IBM Quantum Computers. Our method uses a combination of two parametrized quantum circuits, working in tandem, combined with a variational quantum eigensolver to iteratively find the eigenstates of a molecular Hamiltonian
Clam survival in chlorinated water
Applications of 10 to 40 ppM chlorine were ineffective in control of Asiatic clams that had colonized the suction well of a cooling water pump for one of the Savannah River production reactors. Accumulated mud on the floors and walls of the basin protected large numbers of clams from lethal chlorine exposures. After clams were removed from chlorine exposures of 9, 17, 25, and 54 hours, respective survivals after seven days in a recovery chamber were 97 percent, 84 percent, 47 percent, and 10 percent. Of the clams that were protected by mud during the entire test (54 hours), 65 percent were alive after seven days in the recovery chamber. (auth
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