1,025 research outputs found
Tavis-Cummings model and collective multi-qubit entanglement in trapped ions
We present a method of generating collective multi-qubit entanglement via
global addressing of an ion chain following the guidelines of the
Tavis-Cummings model, where several qubits are coupled to a collective motional
mode. We show that a wide family of Dicke states and irradiant states can be
generated by single global laser pulses, unitarily or helped with suitable
postselection techniques.Comment: 6 pages, 3 figures. Accepted for publication in Physical Review
The Dynamics of Hybrid Metabolic-Genetic Oscillators
The synthetic construction of intracellular circuits is frequently hindered
by a poor knowledge of appropriate kinetics and precise rate parameters. Here,
we use generalized modeling (GM) to study the dynamical behavior of topological
models of a family of hybrid metabolic-genetic circuits known as
"metabolators." Under mild assumptions on the kinetics, we use GM to
analytically prove that all explicit kinetic models which are topologically
analogous to one such circuit, the "core metabolator," cannot undergo Hopf
bifurcations. Then, we examine more detailed models of the metabolator.
Inspired by the experimental observation of a Hopf bifurcation in a
synthetically constructed circuit related to the core metabolator, we apply GM
to identify the critical components of the synthetically constructed
metabolator which must be reintroduced in order to recover the Hopf
bifurcation. Next, we study the dynamics of a re-wired version of the core
metabolator, dubbed the "reverse" metabolator, and show that it exhibits a
substantially richer set of dynamical behaviors, including both local and
global oscillations. Prompted by the observation of relaxation oscillations in
the reverse metabolator, we study the role that a separation of genetic and
metabolic time scales may play in its dynamics, and find that widely separated
time scales promote stability in the circuit. Our results illustrate a generic
pipeline for vetting the potential success of a potential circuit design,
simply by studying the dynamics of the corresponding generalized model
Genome-scale architecture of small molecule regulatory networks and the fundamental trade-off between regulation and enzymatic activity
Metabolic flux is in part regulated by endogenous small molecules that modulate the catalytic activity of an enzyme, e.g., allosteric inhibition. In contrast to transcriptional regulation of enzymes, technical limitations have hindered the production of a genome-scale atlas of small molecule-enzyme regulatory interactions. Here, we develop a framework leveraging the vast, but fragmented, biochemical literature to reconstruct and analyze the small molecule regulatory network (SMRN) of the model organism Escherichia coli, including the primary metabolite regulators and enzyme targets. Using metabolic control analysis, we prove a fundamental trade-off between regulation and enzymatic activity, and we combine it with metabolomic measurements and the SMRN to make inferences on the sensitivity of enzymes to their regulators. Generalizing the analysis to other organisms, we identify highly conserved regulatory interactions across evolutionarily divergent species, further emphasizing a critical role for small molecule interactions in the maintenance of metabolic homeostasis.P30 CA008748 - NCI NIH HHS; R01 GM121950 - NIGMS NIH HH
Rotation Prevents Finite-Time Breakdown
We consider a two-dimensional convection model augmented with the rotational
Coriolis forcing, , with a fixed
being the inverse Rossby number. We ask whether the action of dispersive
rotational forcing alone, , prevents the generic finite time breakdown
of the free nonlinear convection. The answer provided in this work is a
conditional yes. Namely, we show that the rotating Euler equations admit global
smooth solutions for a subset of generic initial configurations. With other
configurations, however, finite time breakdown of solutions may and actually
does occur. Thus, global regularity depends on whether the initial
configuration crosses an intrinsic, critical threshold, which
is quantified in terms of the initial vorticity, ,
and the initial spectral gap associated with the initial velocity
gradient, . Specifically, global regularity of the rotational Euler equation is
ensured if and only if . We also prove that the velocity field remains smooth if and
only if it is periodic. We observe yet another remarkable periodic behavior
exhibited by the {\em gradient} of the velocity field. The spectral dynamics of
the Eulerian formulation reveals that the vorticity and the eigenvalues (and
hence the divergence) of the flow evolve with their own path-dependent period.
We conclude with a kinetic formulation of the rotating Euler equation
Dynamics of Vortex Pair in Radial Flow
The problem of vortex pair motion in two-dimensional plane radial flow is
solved. Under certain conditions for flow parameters, the vortex pair can
reverse its motion within a bounded region. The vortex-pair translational
velocity decreases or increases after passing through the source/sink region,
depending on whether the flow is diverging or converging, respectively. The
rotational motion of two corotating vortexes in a quiescent environment
transforms into motion along a logarithmic spiral in the presence of radial
flow. The problem may have applications in astrophysics and geophysics.Comment: 13 pages, 9 figure
Intelligent Malingering in the Setting of Porphyria Variegata: A Rare Occurrence on Both Fronts
Malingering can be a difficult diagnosis to discern, especially in patients with well-crafted stories presenting with signs and symptoms that align directly with the literature. This can further become a challenge when a patient is malingering in the setting of a rare disease, where many complaints can be subjective in nature and not entirely testable by physical exam alone. Malingering is responsible for billions of dollars of healthcare waste every single year, and this report can serve as a guide of history elements, signs and symptoms to look out for with patients malingering in the setting of the porphyrias. It is important to recognize when patients are malingering, and when they are not, so that they may receive the appropriate care to help with their condition. This report can also serve as a guideline for what laboratory tests and studies to order in the setting of a suspected porphyria case, in order to confirm the diagnosis and get the patient the appropriate treatment regimen. Intelligent malingering is a growing problem, especially with the amount of access the general public has to medical information, and it is important for us to be able to identify when a patient is truly suffering from a rare disease and when they are malingering
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