Among the alternative host materials for solid polymer electrolytes (SPEs), polycarbonates have recently shown promising functionality in all-solid-state lithium batteries from ambient to elevated ...temperatures. While the computational and experimental investigations of ion conduction in conventional polyethers have been extensive, the ion transport in polycarbonates has been much less studied. The present work investigates the ionic transport behavior in SPEs based on poly(trimethylene carbonate) (PTMC) and its co-polymer with ε-caprolactone (CL) via both experimental and computational approaches. FTIR spectra indicated a preferential local coordination between Li(+) and ester carbonyl oxygen atoms in the P(TMC20CL80) co-polymer SPE. Diffusion NMR revealed that the co-polymer SPE also displays higher ion mobilities than PTMC. For both systems, locally oriented polymer domains, a few hundred nanometers in size and with limited connections between them, were inferred from the NMR spin relaxation and diffusion data. Potentiostatic polarization experiments revealed notably higher cationic transference numbers in the polycarbonate based SPEs as compared to conventional polyether based SPEs. In addition, MD simulations provided atomic-scale insight into the structure-dynamics properties, including confirmation of a preferential Li(+)-carbonyl oxygen atom coordination, with a preference in coordination to the ester based monomers. A coupling of the Li-ion dynamics to the polymer chain dynamics was indicated by both simulations and experiments.
Human mitochondrial transcription factor A (TFAM) is a high-mobility group (HMG) protein at the nexus of mitochondrial DNA (mtDNA) replication, transcription, and inheritance. Little is known about ...the mechanisms underlying its posttranslational regulation. Here, we demonstrate that TFAM is phosphorylated within its HMG box 1 (HMG1) by cAMP-dependent protein kinase in mitochondria. HMG1 phosphorylation impairs the ability of TFAM to bind DNA and to activate transcription. We show that only DNA-free TFAM is degraded by the Lon protease, which is inhibited by the anticancer drug bortezomib. In cells with normal mtDNA levels, HMG1-phosphorylated TFAM is degraded by Lon. However, in cells with severe mtDNA deficits, nonphosphorylated TFAM is also degraded, as it is DNA free. Depleting Lon in these cells increases levels of TFAM and upregulates mtDNA content, albeit transiently. Phosphorylation and proteolysis thus provide mechanisms for rapid fine-tuning of TFAM function and abundance in mitochondria, which are crucial for maintaining and expressing mtDNA.
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► cAMP-dependent protein kinase (PKA) serine phosphorylates TFAM within HMG1 ► HMG1 phosphorylation of TFAM impairs DNA binding and transcription activation ► Lon protease selectively degrades DNA-free TFAM and is inhibited by bortezomib ► Lon knockdown stabilizes TFAM in mtDNA-deficient cells and upregulates mtDNA
Electric Field Effect in Atomically Thin Carbon Films Novoselov, K. S.; Geim, A. K.; Morozov, S. V. ...
Science (American Association for the Advancement of Science),
10/2004, Letnik:
306, Številka:
5696
Journal Article
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We describe monocrystalline graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are found to be a ...two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar electric field effect such that electrons and holes in concentrations up to 1013per square centimeter and with room-temperature mobilities of ~10,000 square centimeters per volt-second can be induced by applying gate voltage.
Although graphite is known as one of the most chemically inert materials, we have found that graphene, a single atomic plane of graphite, can react with atomic hydrogen, which transforms this highly ...conductive zero-overlap semimetal into an insulator. Transmission electron microscopy reveals that the obtained graphene derivative (graphane) is crystalline and retains the hexagonal lattice, but its period becomes markedly shorter than that of graphene. The reaction with hydrogen is reversible, so that the original metallic state, the lattice spacing, and even the quantum Hall effect can be restored by annealing. Our work illustrates the concept of graphene as a robust atomic-scale scaffold on the basis of which new two-dimensional crystals with designed electronic and other properties can be created by attaching other atoms and molecules.
Quantum electrodynamics (resulting from the merger of quantum mechanics and relativity theory) has provided a clear understanding of phenomena ranging from particle physics to cosmology and from ...astrophysics to quantum chemistry. The ideas underlying quantum electrodynamics also influence the theory of condensed matter, but quantum relativistic effects are usually minute in the known experimental systems that can be described accurately by the non-relativistic Schrödinger equation. Here we report an experimental study of a condensed-matter system (graphene, a single atomic layer of carbon) in which electron transport is essentially governed by Dirac's (relativistic) equation. The charge carriers in graphene mimic relativistic particles with zero rest mass and have an effective 'speed of light' c* 106 m s-1. Our study reveals a variety of unusual phenomena that are characteristic of two-dimensional Dirac fermions. In particular we have observed the following: first, graphene's conductivity never falls below a minimum value corresponding to the quantum unit of conductance, even when concentrations of charge carriers tend to zero; second, the integer quantum Hall effect in graphene is anomalous in that it occurs at half-integer filling factors; and third, the cyclotron mass mc of massless carriers in graphene is described by E = mcc*2. This two-dimensional system is not only interesting in itself but also allows access to the subtle and rich physics of quantum electrodynamics in a bench-top experiment.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We find a family of Lax representations with a non-removable parameter for the Euler equation of dynamics of an inviscid incompressible fluid in vorticity form on a two-dimensional Riemannian ...manifold.
Recent developments in the technology of van der Waals heterostructures made from two-dimensional atomic crystals have already led to the observation of new physical phenomena, such as the ...metal-insulator transition and Coulomb drag, and to the realization of functional devices, such as tunnel diodes, tunnel transistors and photovoltaic sensors. An unprecedented degree of control of the electronic properties is available not only by means of the selection of materials in the stack, but also through the additional fine-tuning achievable by adjusting the built-in strain and relative orientation of the component layers. Here we demonstrate how careful alignment of the crystallographic orientation of two graphene electrodes separated by a layer of hexagonal boron nitride in a transistor device can achieve resonant tunnelling with conservation of electron energy, momentum and, potentially, chirality. We show how the resonance peak and negative differential conductance in the device characteristics induce a tunable radiofrequency oscillatory current that has potential for future high-frequency technology.
Magnetic micro- and nanoparticles propelled by a rotating magnetic field provide a new technology for targeted drug delivery. The therapeutic effect of the technology is achievable with the ...collective action of large groups (swarms) of the motors. Narrowing of the swarm width before it reaches the target or,
vice versa
, its expansion prior to deposition on the channel walls are of high importance. Here we show how such swarm tuning can be achieved using a combination of the in-plane rotating and static magnetic field acting in the same plane. Although for this asymmetric actuating field the steady synchronous solutions of the problem do not materialize, the developed approach admits an analytical consideration for the average motor orientation and propulsion. The unique property of an average motion in the actuation by an asymmetric magnetic field is the emergence of propeller's net drift in plane of the field rotation. The drift velocity can be comparable in magnitude to the propulsion velocity along the axis of the field rotation. The field-induced drift is studied in detail for achiral V-shaped and chiral helical propellers, depending on their magnetization. Finally, we suggest spatial configuration of the constant magnetic field capable of focusing/defocusing swarms of magnetic motors.
The right-handed magnetic helices are focused in the rotating magnetic field and azymuthal field of a linear current.
Thermodiffusion of binary mixtures in an inhomogeneous temperature field is due to scattering phenomena and the effects of interparticle interactions. Accordingly, when describing the Soret ...coefficient, it is customary to distinguish between the kinetic and the chemical contributions. Predicting thermodiffusion even in simple binary mixtures is challenging because of numerous factors that influence these contributions. Here, we present a comprehensive theoretical study of both contributions and make predictions of the Soret coefficient for 141 equimolar binary mixtures composed of 24 nonassociating and non- or weakly polar simple liquids. The chemical contribution is an equilibrium property related to the gradient of a partial pressure of one of the mixture components. It is successfully described within the framework of the perturbed-chain statistical associating fluid theory, characterizing the pure liquids by only three physically significant parameters: the segment number, the hard-core segment diameter, and the segment–segment interaction parameter. The nonequilibrium kinetic contribution is approximated by the relation associated with hydrodynamic fluctuations. The sum of the chemical and kinetic contributions determines the Soret coefficient of the mixture. Both contributions are found for the case of dilute mixtures. The equimolar value of the Soret coefficient is calculated as the arithmetic mean of its limiting values. The predicted values of the Soret coefficient are compared with the experimental data available for 113 mixtures. Overall, the theoretical and experimental results are in good agreement with each other. For 70 mixtures, the difference of data does not exceed 0.002 K–1. The best agreement between the data occurs for the alkanes. The maximum deviations of the results are observed for mixtures with 1-methylnaphthalene, bromonaphthalene, and cyclohexane. We relate these deviations to the plate-like shape of their molecules, which is not taken into account when deriving the kinetic contribution.
Coupled twiss parameters estimation from turn-by-turn data Morozov, I.; Maltseva, Yu
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
September 2024, 2024-09-00, Letnik:
1066
Journal Article
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Linear optics parameters are often estimated using turn-by-turn (TbT) data. In-plane beta functions, which are the most common measurement objectives, can be estimated from the amplitudes or phases ...of TbT data, providing an overall characterization of the linear lattice. In addition to estimating uncoupled Twiss parameters, TbT data can also be utilized for characterizing coupled linear motion. We investigate several methods for constructing a full normalization matrix at each beam position monitor (BPM). BPMs provide information on beam centroid transverse coordinates, but direct observation of transverse momenta is not available. To estimate momenta, one can use a pair of BPMs or fit data obtained from several BPMs. By using both coordinates and momenta, it is possible to fit the one-turn matrix (or its power) at each BPM, allowing for the computation of coupled Twiss parameters. Another approach involves the minimization of side peak amplitudes in the spectrum of normalized complex coordinates. Similarly, the normalization matrix can be estimated by fitting linear coupled invariants. In this study, we derive and utilize a special form of the normalization matrix, which remains non-singular in the zero coupling limit. Coupled Twiss parameters can be obtained from the normalization matrix. The paper presents the results of applying and comparing these methods to both modeled and measured VEPP-4M TbT data, demonstrating effective estimation of coupled Twiss parameters.
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