1,642 research outputs found
Response of the lattice across the filling-controlled Mott metal-insulator transition of a rare earth titanate
The lattice response of a prototype Mott insulator, SmTiO3, to hole doping is
investigated with atomic-scale spatial resolution. SmTiO3 films are doped with
Sr on the Sm site with concentrations that span the insulating and metallic
sides of the filling-controlled Mott metal-insulator transition (MIT). The
GdFeO3-type distortions are investigated using an atomic resolution scanning
transmission electron microscopy technique that can resolve small lattice
distortions with picometer precision. We show that these distortions are
gradually and uniformly reduced as the Sr concentration is increased without
any phase separation. Significant distortions persist into the metallic state.
The results present a new picture of the physics of this prototype
filling-controlled MIT, which is discussed.Comment: Accepted, Phys. Rev. Let
Load Capacity Improvements in Nucleic Acid Based Systems Using Partially Open Feedback Control
Synthetic biology is facilitating novel methods and components to build in vivo and in vitro circuits to better understand and re-engineer biological networks. Recently, Kim and Winfree have synthesized a remarkably elegant network of transcriptional oscillators in vitro using a modular architecture of synthetic gene analogues and a few enzymes that, in turn, could be used to drive a variety of downstream circuits and nanodevices. However, these oscillators are sensitive to initial conditions and downstream load processes. Furthermore, the oscillations are not sustained since the inherently closed design suffers from enzyme deactivation, NTP fuel exhaustion, and waste product build up. In this paper, we show that a partially open architecture in which an ℒ_1 adaptive controller, implemented inside an in silico computer that resides outside the wet-lab apparatus, can ensure sustained tunable oscillations in two specific designs of the Kim–Winfree oscillator networks. We consider two broad cases of operation: (1) the oscillator network operating in isolation and (2) the oscillator network driving a DNA tweezer subject to a variable load. In both scenarios, our simulation results show a significant improvement in the tunability and robustness of these oscillator networks. Our approach can be easily adopted to improve the loading capacity of a wide range of synthetic biological devices
Functions holomorphic along holomorphic vector fields
The main result of the paper is the following generalization of Forelli's
theorem: Suppose F is a holomorphic vector field with singular point at p, such
that F is linearizable at p and the matrix is diagonalizable with the
eigenvalues whose ratios are positive reals. Then any function that has
an asymptotic Taylor expansion at p and is holomorphic along the complex
integral curves of F is holomorphic in a neighborhood of p.
We also present an example to show that the requirement for ratios of the
eigenvalues to be positive reals is necessary
Patenting activity in the food safety sector
Research on science and technology policy has heavily relied on patent data. However, relatively few studies of food safety patent activity appear in scholarly literature. This paper provides a discussion on patents as a measure of new knowledge generation in the food safety sector. In so doing, there are inherent challenges to identifying a research taxonomy for this multidisciplinary area. To overcome these challenges, the paper uses a natural language approach that can be applied to other research areas where boundaries of fields are not well defined
Spin and charge correlations across the metal-to-insulator crossover in the half-filled Hubbard model
The Hubbard model with nearest-neighbour hopping on the square lattice
and an average of one electron per site is known to undergo an extended
crossover from metallic to insulating behavior driven by proliferating
antiferromagnetic correlations. We study signatures of this crossover in spin
and charge correlation functions and present results obtained with controlled
accuracy using diagrammatic Monte Carlo in the range of parameters amenable to
experimental verification with ultracold atoms in optical lattices. The
qualitative changes in charge and spin correlations associated with the
crossover are observed at well-separated temperature scales, which encase the
intermediary regime of non-Fermi-liquid character, where local magnetic moments
are formed and non-local fluctuations in both channels are essential.Comment: 6 pages, 5 figures, published versio
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