4,127 research outputs found
Non-Markovian dynamics in the theory of full counting statistics
We consider the theoretical description of real-time counting of electrons
tunneling through a Coulomb-blockade quantum dot using a detector with finite
bandwidth. By tracing out the quantum dot we find that the dynamics of the
detector effectively is non-Markovian. We calculate the cumulant generating
function corresponding to the resulting non-Markovian rate equation and find
that the measured current cumulants behave significantly differently compared
to those of a Markovian transport process. Our findings provide a novel
interpretation of noise suppression found in a number of systems.Comment: 4 pages, 1 figure, Contribution to ICNF 2007, Tokyo, Japan,
September, 200
Counting statistics of transport through Coulomb blockade nanostructures: High-order cumulants and non-Markovian effects
Recent experimental progress has made it possible to detect in real-time
single electrons tunneling through Coulomb blockade nanostructures, thereby
allowing for precise measurements of the statistical distribution of the number
of transferred charges, the so-called full counting statistics. These
experimental advances call for a solid theoretical platform for equally
accurate calculations of distribution functions and their cumulants. Here we
develop a general framework for calculating zero-frequency current cumulants of
arbitrary orders for transport through nanostructures with strong Coulomb
interactions. Our recursive method can treat systems with many states as well
as non-Markovian dynamics. We illustrate our approach with three examples of
current experimental relevance: bunching transport through a two-level quantum
dot, transport through a nano-electromechanical system with dynamical
Franck-Condon blockade, and transport through coherently coupled quantum dots
embedded in a dissipative environment. We discuss properties of high-order
cumulants as well as possible subtleties associated with non-Markovian
dynamics.Comment: 27 pages, 8 figures, 1 table, final version as published in Phys.
Rev.
DNA wrapping around MWNTs and graphene: a SERS study
In recent years, carbon nanostructure as nanotubes (CNTs) and graphene are at the centre of a significant research effort due to the strong scientific and technological interest because of their unique physical and chemical properties: large surface area, excellent thermal and electric conductivity, high electron transfer kinetics and strong mechanical strength. Recently, a great attention has been paid to the interaction of DNA with carbon-based nanostructures such as C60, multiwalled-nanotubes (MWNTs), single-walled nanotubes (SWNTs) and graphene. The development of these studies is motivated by a wide spectrum of possible use of these materials e.g. as biosensors, drug delivery agents and diagnosis tools. In this work, we applied surface-enhanced Raman spectroscopy (SERS) to the study of DNA/MWNTs and DNA/graphene systems
Surface-Enhanced Raman Spectroscopy Characterization of Pristine and Functionalized Carbon Nanotubes and Graphene
Carbon nanotubes (CNTs) and graphene are at the center of a significant research effort due to their unique physical and chemical properties, which promise high technological impact. For the future development of all the foreseen applications, it is of particular interest the study of binding interactions between carbon nanostructures and functional groups. An appropriate method is the surface-enhanced Raman spectroscopy (SERS), which provides a large amplification of Raman signals when the probed molecule is adsorbed on a nanosized metallic surface. In this chapter, we present a review of principal results obtained applying SERS for the characterization of pristine and functionalized CNTs and graphene. The obtained results encourage us to consider SERS as a powerful method to obtain a rapid monitor of the procedures used to interface graphene and nanotubes
Photosynthesis regulation in response to fluctuating light in the secondary endosymbiont alga Nannochloropsis gaditana
In nature, photosynthetic organisms are exposed to highly dynamic environmental conditions where the excitation energy and electron flow in the photosynthetic apparatus need to be continuously modulated. Fluctuations in incident light are particularly challenging since they drive oversaturation of photosynthesis, with consequent oxidative stress and photoinhibition. Plants and algae have evolved several mechanisms to modulate their photosynthetic machinery to cope with light dynamics, such as thermal dissipation of excited chlorophyll states (Non-Photochemical Quenching, NPQ) and regulation of electron transport. The regulatory mechanisms involved in the response to light dynamics have adapted during evolution and exploring biodiversity is a valuable strategy for expanding our understanding of their biological roles. In this work, we investigated the response to fluctuating light in Nannochloropsis gaditana, a eukaryotic microalga of the phylum Heterokonta originating from a secondary endosymbiotic event. N. gaditana is negatively affected by light fluctuations, leading to large reductions in growth and photosynthetic electron transport. Exposure to light fluctuations specifically damages photosystem I, likely because of ineffective regulation of electron transport in this species. The role of Non-Photochemical Quenching, also assessed using a mutant strain specifically depleted of this response, was instead found to be minor, especially in responding to the fastest light fluctuations
The Ratchet effect in an ageing glass
We study the dynamics of an asymmetric intruder in a glass-former model. At
equilibrium, the intruder diffuses with average zero velocity. After an abrupt
quench to deeply under the mode-coupling temperature, a net average drift
is observed, steady on a logarithmic time-scale. The phenomenon is well
reproduced in an asymmetric version of the Sinai model. The subvelocity of the
intruder grows with , where is defined by the
response-correlation ratio, corresponding to a general behavior of thermal
ratchets when in contact with two thermal reservoirs.Comment: 10 pages, 4 figure
Continuous Plant-Based and Remote Sensing for Determination of Fruit Tree Water Status
Climate change poses significant challenges to agricultural productivity, making the efficient management of water resources essential for sustainable crop production. The assessment of plant water status is crucial for understanding plant physiological responses to water stress and optimizing water management practices in agriculture. Proximal and remote sensing techniques have emerged as powerful tools for the non-destructive, efficient, and spatially extensive monitoring of plant water status. This review aims to examine the recent advancements in proximal and remote sensing methodologies utilized for assessing the water status, consumption, and irrigation needs of fruit tree crops. Several proximal sensing tools have proved useful in the continuous estimation of tree water status but have strong limitations in terms of spatial variability. On the contrary, remote sensing technologies, although less precise in terms of water status estimates, can easily cover from medium to large areas with drone or satellite images. The integration of proximal and remote sensing would definitely improve plant water status assessment, resulting in higher accuracy by integrating temporal and spatial scales. This paper consists of three parts: the first part covers current plant-based proximal sensing tools, the second part covers remote sensing techniques, and the third part includes an update on the on the combined use of the two methodologies
Antenna complexes protect Photosystem I from Photoinhibition
Background
Photosystems are composed of two moieties, a reaction center and a peripheral antenna system. In photosynthetic eukaryotes the latter system is composed of proteins belonging to Lhc family. An increasing set of evidences demonstrated how these polypeptides play a relevant physiological function in both light harvesting and photoprotection. Despite the sequence similarity between antenna proteins associated with the two Photosystems, present knowledge on their physiological role is mostly limited to complexes associated to Photosystem II.
Results
In this work we analyzed the physiological role of Photosystem I antenna system in Arabidopsis thaliana both in vivo and in vitro. Plants depleted in individual antenna polypeptides showed a reduced capacity for photoprotection and an increased production of reactive oxygen species upon high light exposure. In vitro experiments on isolated complexes confirmed that depletion of antenna proteins reduced the resistance of isolated Photosystem I particles to high light and that the antenna is effective in photoprotection only upon the interaction with the core complex.
Conclusions
We show that antenna proteins play a dual role in Arabidopsis thaliana Photosystem I photoprotection: first, a Photosystem I with an intact antenna system is more resistant to high light because of a reduced production of reactive oxygen species and, second, antenna chlorophyll-proteins are the first target of high light damages. When photoprotection mechanisms become insufficient, the antenna chlorophyll proteins act as fuses: LHCI chlorophylls are degraded while the reaction center photochemical activity is maintained. Differences with respect to photoprotection strategy in Photosystem II, where the reaction center is the first target of photoinhibition, are discussed
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