186 research outputs found
Strongly-Driven One-Atom Laser and Decoherence Monitoring
We propose the implementation of a strongly-driven one-atom laser, based on
the off-resonant interaction of a three-level atom in -configuration
with a single cavity mode and three laser fields. We show that the system can
be described equivalently by a two-level atom resonantly coupled to the cavity
and driven by a strong effective coherent field. The effective dynamics can be
solved exactly, including a thermal field bath, allowing an analytical
description of field statistics and entanglement properties. We also show the
possible generation of Schr\"odinger cat states for the whole atom-field system
and for the field alone after atomic measurement. We propose a way to monitor
the system decoherence by measuring atomic population. Finally, we confirm the
validity of our model through numerical solutions.Comment: 9 pages, 7 figures Accepted in Phys. Rev.
Innovative crop and weed management strategies for organic spinach: crop yield and weed suppression.
In organic agriculture, it is important to tackle crop and weed management from a system perspective to make it effective, especially in poorly competitive crops such as vegetables. For that reason, we developed two innovative integrated crop and weed management systems for a field vegetable crop sequence in a commercial organic farm that we have been comparing to a standard farm system from 2006 to 2008. The three systems are applied to a spinach-potato-cabbage-tomato two-year crop sequence and include different levels of technical innovation: Standard Crop Management System (SCMS); Intermediate Crop Management System (ICMS); and Advanced Crop Management System (ACMS). ICMS is based on a sequence of physical weed management treatments, whereas ACMS also includes a subterranean clover (Trifolium subterraneum) living mulch. In this paper we analyse the results obtained on spinach (Spinacia oleracea) in terms of crop yield and weed suppression. Both innovative systems increased total spinach fresh weight yield compared to SCMS, despite higher weed biomass. In ACMS, total weed biomass decreased linearly with increasing biomass of the subterranean clover living mulch
A learning-based algorithm to quickly compute good primal solutions for Stochastic Integer Programs
We propose a novel approach using supervised learning to obtain near-optimal
primal solutions for two-stage stochastic integer programming (2SIP) problems
with constraints in the first and second stages. The goal of the algorithm is
to predict a "representative scenario" (RS) for the problem such that,
deterministically solving the 2SIP with the random realization equal to the RS,
gives a near-optimal solution to the original 2SIP. Predicting an RS, instead
of directly predicting a solution ensures first-stage feasibility of the
solution. If the problem is known to have complete recourse, second-stage
feasibility is also guaranteed. For computational testing, we learn to find an
RS for a two-stage stochastic facility location problem with integer variables
and linear constraints in both stages and consistently provide near-optimal
solutions. Our computing times are very competitive with those of
general-purpose integer programming solvers to achieve a similar solution
quality
DNA Damage Response Protein CHK2 Regulates Metabolism in Liver Cancer
Defective mitosis with chromosome missegregation can have a dramatic effect on genome integrity by causing DNA damage, activation of the DNA damage response (DDR), and chromosomal instability. Although this is an energy-dependent process, mechanisms linking DDR to cellular metabolism are unknown. Here we show that checkpoint kinase 2 (CHK2), a central effector of DDR, regulates cellular energy production by affecting glycolysis and mitochondrial functions. Patients with hepatocellular carcinoma (HCC) had increased CHK2 mRNA in blood, which was associated with elevated tricarboxylic acid cycle (TCA) metabolites. CHK2 controlled expression of succinate dehydrogenase (SDH) and intervened with mitochondrial functions. DNA damage and CHK2 promoted SDH activity marked by increased succinate oxidation through the TCA cycle; this was confirmed in a transgenic model of HCC with elevated DNA damage. Mitochondrial analysis identified CHK2-controlled expression of SDH as key in sustaining reactive oxygen species production. Cells with DNA damage and elevated CHK2 relied significantly on glycolysis for ATP production due to dysfunctional mitochondria, which was abolished by CHK2 knockdown. This represents a vulnerability created by the DNA damage response that could be exploited for development of new therapies
Solvable model of a strongly-driven micromaser
We study the dynamics of a micromaser where the pumping atoms are strongly
driven by a resonant classical field during their transit through the cavity
mode. We derive a master equation for this strongly-driven micromaser,
involving the contributions of the unitary atom-field interactions and the
dissipative effects of a thermal bath. We find analytical solutions for the
temporal evolution and the steady-state of this system by means of phase-space
techniques, providing an unusual solvable model of an open quantum system,
including pumping and decoherence. We derive closed expressions for all
relevant expectation values, describing the statistics of the cavity field and
the detected atomic levels. The transient regime shows the build-up of mixtures
of mesoscopic fields evolving towards a superpoissonian steady-state field
that, nevertheless, yields atomic correlations that exhibit stronger
nonclassical features than the conventional micromaser.Comment: 9 pages, 16 figures. Submitted for publicatio
Exact results on decoherence and entanglement in a system of N driven atoms and a dissipative cavity mode
We solve the dynamics of an open quantum system where N strongly driven
two-level atoms are equally coupled on resonance to a dissipative cavity mode.
Analytical results are derived on decoherence, entanglement, purity, atomic
correlations and cavity field mean photon number. We predict decoherence-free
subspaces for the whole system and the N-qubit subsystem, the monitoring of
quantum coherence and purity decay by atomic populations measurements, the
conditional generation of atomic multi-partite entangled states and of cavity
cat-like states. We show that the dynamics of atoms prepared in states
invariant under permutation of any two components remains restricted within the
subspace spanned by the completely symmetric Dicke states. We discuss examples
and applications in the cases N=3,4.Comment: 7 pages, 4 figures, accepted in EPJ
Innovative crop and weed management strategies for organic spinach: crop yield and weed suppression
In organic agriculture, it is important to tackle crop and weed management from a system perspective to make it effective, especially in poorly competitive crops such as vegetables. For that reason, we developed two innovative integrated crop and weed management systems for a field vegetable crop sequence in a commercial organic farm that we have been comparing to a standard farm system from 2006 to 2008. The three systems are applied to a spinach-potato-cabbage-tomato two-year crop sequence and include different levels of technical innovation: Standard Crop Management System (SCMS); Intermediate Crop Management System (ICMS); and Advanced Crop Management System (ACMS). ICMS is based on a sequence of physical weed management treatments, whereas ACMS also includes a subterranean clover (Trifolium subterraneum) living mulch. In this paper we analyse the results obtained on spinach (Spinacia oleracea) in terms of crop yield and weed suppression. Both innovative systems increased total spinach fresh weight yield compared to SCMS, despite higher weed biomass. In ACMS, total weed biomass decreased linearly with increasing biomass of the subterranean clover living mulch
Genetics of migraine and pharmacogenomics: some considerations
Migraine is a complex disorder caused by a combination of genetic and environmental factors
- …