- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
A carbon nanotube-iron (III) oxide nanocomposite as a cathode in dye-sensitized solar cells: Computational modeling and electrochemical investigations
摘要： Here is the evaluating result on the applicability of the multi-walled carbon nanotube (MWCNT) and a-iron (III) oxide (a-Fe2O3) nanocomposite as a cathode material in dye-sensitized solar cells (DSCs). The morphology and the structure of the MWCNT/a-Fe2O3 nanocomposite have characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray elemental mapping analysis. Moreover, the electrochemical performance of the nanocomposite has studied toward the activity of Iˉ/I3ˉ redox couple which represents high current density, low peak-to-peak separation, low charge-transfer resistance, and almost 100% stable response signal. Furthermore, the computational modeling employing the molecular mechanics (MM) and the restricted-Hartree Fock/semiempirical parameterization (RHF/PM6) methods reveals that the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and the HOMO-LUMO energy gap of the modeled nanocomposite are as (cid:1)6.88, (cid:1)3.62, and 3.26 eV, respectively. These properties match with the electronic-level domino of the DSC structure. Finally, the DSC device has fabricated using N719-sensitized TiO2 photoanode and MWCNT/a-Fe2O3 counter electrode, presenting the open-circuit potential, the short-circuit current density, and the power-conversion ef?ciency of 0.7 V, 20.37 mA cmˉ2, and 6.0%, respectively. This study successfully approves the potential of the nanocomposite as a cathode material in iodine-based dye-sensitized solar cells.
关键词： Dye-sensitized solar cell,Nanocomposite,Carbon nanotube,Molecular mechanics,RHF/PM6,Iron (III) oxide
更新于2025-11-21 11:18:25
-
Neptune’s ring arcs: VLT/NACO near-infrared observations and a model to explain their stability
摘要： Context. Neptune’s incomplete ring arcs have been stable since their discovery in 1984 although these structures should be destroyed in a few months through differential Keplerian motion. Regular imaging data are needed to address the question of the arc stability. Aims. We present the first NACO observations of Neptune’s ring arcs taken at 2.2 μm (Ks band) with the Very Large Telescope in August 2007, and propose a model for the arc stability based on co-orbital motion. Methods. The images were aligned using the ephemerides of the satellites Proteus and Triton and were suitably co-added to enhance ring or satellite signals. Resonance theory and N-body simulations were used to model the arcs’ confinement. Results. We derive accurate mean motion values for the arcs and Galatea and confirm the mismatch between the arcs’ position and the location of the 42:43 corotation inclination resonance. We propose a new confinement mechanism where small co-orbital satellites in equilibrium trap ring arc material. We constrain the masses and locations of these hypothetical co-orbital bodies.
关键词： planets and satellites: individual: Neptune,celestial mechanics,techniques: photometric,planets and satellites: rings
更新于2025-09-23 15:23:52
-
Loophole-Free Bell Tests and the Falsification of Local Realism
摘要： Quantum mechanics is strictly incompatible with local realism. It has been shown by Bell and others that it is possible, in principle, to experimentally differentiate between local realism and quantum mechanics. Numerous experiments have attempted to falsify local realism; however, they have consistently failed to close the detection loophole under strict locality conditions, thereby allowing local realistic explanations for their observations. In 2015, three experiments took place that tested local realism without the impediments of these significant loopholes. Between these three experiments, a substantial data set was collected. All of the collected data show a strong violation of local realism and strong support for quantum mechanics. This article reviews the theoretical basis of Bell tests and the affiliated loopholes, as well as the methods employed by these recent experiments and the implications of the results they observed.
关键词： Local Realism,CHSH Inequality,Loophole-Free Bell Test,CH Inequality,Quantum Mechanics
更新于2025-09-23 15:22:29
-
A Quantum Field Approach for Advancing Optical Coherence Tomography Part I: First Order Correlations, Single Photon Interference, and Quantum Noise
摘要： Optical coherence tomography has become an important imaging technology in cardiology and ophthalmology, with other applications under investigations. Major advances in optical coherence tomography (OCT) imaging are likely to occur through a quantum field approach to the technology. In this paper, which is the first part in a series on the topic, the quantum basis of OCT first order correlations is expressed in terms of full field quantization. Specifically first order correlations are treated as the linear sum of single photon interferences along indistinguishable paths. Photons and the electromagnetic (EM) field are described in terms of quantum harmonic oscillators. While the author feels the study of quantum second order correlations will lead to greater paradigm shifts in the field, addressed in part II, advances from the study of quantum first order correlations are given. In particular, ranging errors are discussed (with remedies) from vacuum fluctuations through the detector port, photon counting errors, and position probability amplitude uncertainty. In addition, the principles of quantum field theory and first order correlations are needed for studying second order correlations in part II.
关键词： Plaque,Quantum mechanics,Interferometry,Ophthalmology,Noise,Vacuum,Cardiology,Arthritis,Optical coherence tomography
更新于2025-09-23 15:22:29
-
Joining of AlN and Al with Compositional Graded Layer by Centrifugal Mixed-Powder Method
摘要： In this study, joining of AlN and Al with compositional graded layer is made by centrifugal mixed-powder method (CMPM). The mixed-powder of AlN particles and Al particles is inserted into a spinning mold with bulk-shaped AlN, and then molten Al is poured into the spinning mold with the mixed-powder and bulk-shaped AlN. As a result, the molten Al penetrates into the space between the mixed-powder by the centrifugal force, and at the same time, the Al particles can be melted by heat from the molten Al. Then AlN and Al can be joined with compositional graded layer after solidification. Micromechanics-based analysis is also employed to understand the thermal stress relaxation by the compositional graded layer.
关键词： Joining,Ceramics/metal joining,Thermal stress relaxation,Functionally graded materials (FGMs),Micro-mechanics,Centrifugal mixed-powder method (CMPM)
更新于2025-09-23 15:22:29
-
Elastic constants and phonon dispersion relation analysis of graphene sheet with varied Poisson's ratio
摘要： Through the achievement of elastic parameter equivalence by the structural mechanics method, the beam–truss space frame model for graphene sheet has been simpli?ed; moreover a representative unit cell of the periodic graphene structure has been extracted. On this basis, the Bloch theorem is combined with the ?nite element method to determine the phonon dispersion relation of graphene. For the widely used thickness values of the carbon–carbon (C–C) bond, the aspect ratios (thickness/length) are so large that the shear deformation should be considered such that as a result, the negative Poisson's ratio (NPR) characteristic of the C–C bond is observed. Analytical expressions for the elastic constants of graphene sheet have been obtained with varied C–C bond Poisson's ratios. The reasonable coherence with previous results reveals the e?ectiveness of the structural mechanics method for analysing the mechanical properties of nanostructures. The e?ect of deformation modes on the phonon dispersion relation of graphene sheet is further discussed; it is concluded that the acoustic phonon modes are sensitive to the deformation modes of the C–C bond, whereas these deformation modes negligibly in?uence the optical phonon modes. The numerical results also reveal that the shear deformation and the resulting NPR e?ect play an important role in the mechanical property analysis of graphene sheet. To summarise, the interrelation between NPR materials and nano materials has stimulated a wide ?eld of research; moreover, numerous novel phenomena have been observed.
关键词： Elastic constants,Poisson's ratio,Phonon dispersion relation,Graphene sheet,Structural mechanics method
更新于2025-09-23 15:22:29
-
Gramicidin Lateral Distribution in Phospholipid Membranes: Fluorescence Phasor Plots and Statistical Mechanical Model
摘要： When using small mole fraction increments to study gramicidins in phospholipid membranes, we found that the phasor dots of intrinsic ?uorescence of gramicidin D and gramicidin A in dimyristoyl-sn-glycero-3-phosphocholine (DMPC) unilamellar and multilamellar vesicles exhibit a biphasic change with peptide content at 0.143 gramicidin mole fraction. To understand this phenomenon, we developed a statistical mechanical model of gramicidin/DMPC mixtures. Our model assumes a sludge-like mixture of ?uid phase and aggregates of rigid clusters. In the ?uid phase, gramicidin monomers are randomly distributed. A rigid cluster is formed by a gramicidin dimer and DMPC molecules that are condensed to the dimer, following particular stoichiometries (critical gramicidin mole fractions, Xcr including 0.143). Rigid clusters form aggregates in which gramicidin dimers are regularly distributed, in some cases, even to superlattices. At Xcr, the size of cluster aggregates and regular distributions reach a local maximum. Before a similar model was developed for cholesterol/DMPC mixtures (Sugar and Chong (2012) J. Am. Chem. Soc. 134, 1164–1171) and here the similarities and differences are discussed between these two models.
关键词： lipid bilayers,membrane organization,gramicidins,statistical mechanics,?uorescence spectroscopy,peptide-lipid interactions
更新于2025-09-23 15:21:21
-
On the quantum-mechanics of a single photon
摘要： It is shown that a Dirac(-type) equation for a rank-two bi-spinor field ψph on Minkowski (configuration) spacetime furnishes a Lorentz-covariant quantum-mechanical wave equation in position-space representation for a single free photon. This equation does not encounter any of the roadblocks that have obstructed previous attempts (by various authors) to formulate a quantum-mechanical photon wave equation. In particular, it implies that the photon wave function ψph yields conserved non-negative Born-rule-type quantum probabilities and that its probability current density four-vector transforms properly under Lorentz transformations. Moreover, the eigenvalues of the pertinent photon Dirac Hamiltonian and the vector eigenvalues of the photon momentum operator yield the familiar Einstein relations E = ?ω and p = ?k, respectively. Furthermore, these spin-1 wave modes are automatically transversal without the need of an additional constraint on the initial data. Some comments on other proposals to set up a photon wave equation are supplied as well.
关键词： probability current,wave function,quantum-mechanics,photon,Dirac-type equation,Born-rule,Einstein relations,transversal modes,Lorentz-covariant
更新于2025-09-23 15:21:21
-
Probing Cell Mechanics with Bead-Free Optical Tweezers in the <em>Drosophila</em> Embryo
摘要： Morphogenesis requires coordination between genetic patterning and mechanical forces to robustly shape the cells and tissues. Hence, a challenge to understand morphogenetic processes is to directly measure cellular forces and mechanical properties in vivo during embryogenesis. Here, we present a setup of optical tweezers coupled to a light sheet microscope, which allows to directly apply forces on cell-cell contacts of the early Drosophila embryo, while imaging at a speed of several frames per second. This technique has the advantage that it does not require the injection of beads into the embryo, usually used as intermediate probes on which optical forces are exerted. We detail step by step the implementation of the setup, and propose tools to extract mechanical information from the experiments. By monitoring the displacements of cell-cell contacts in real time, one can perform tension measurements and investigate cell contacts' rheology.
关键词： Drosophila embryo,Developmental Biology,in vivo imaging,optical tweezers,Light sheet microscopy,force measurements,Issue 141,cell mechanics
更新于2025-09-23 15:21:01
-
Desarrollo de un simulador para el protocolo de criptografía cuántica E91 en un ambiente distribuido
摘要： The objective of this research work is the development of an application which is capable of simulating the behavior of one of the main developed protocols of quantum cryptography, the protocol E91. In order to achieve this objective, it was essential to carry out an exhaustive investigation of the main concepts, principles and theorems of quantum mechanics; as well as the study of other quantum cryptographic protocols and their development today. With all the collected information, the development of the application begun, starting with the definition of the requirements, then implementing and subsequently testing the application, which allows compiling all the work of analysis and design. The obtained results show the strengths and weaknesses of the application for the secure distribution of a quantum final key. Although this work is primarily the development of the implementation that simulates the behavior of the E91 protocol, it is essentially demonstrative.
关键词： Quantum mechanics,quantum protocol E91,RMI,quantum cryptography,E91 simulator,distributed programming
更新于2025-09-23 15:21:01