502 research outputs found
On the dragging of light by a rotating medium
When light is passing through a rotating medium the optical polarization is rotated. Recently, it has been reasoned that this rotation applies also to the transmitted image. We examine these two phenomena by extending an analysis of Player (Player 1976 Proc. R. Soc. A 349, 441-445) to general electromagnetic fields. We find that in this more general case, the wave equation inside the rotating medium has to be amended by a term which is connected to the orbital angular momentum (OAM) of the light. We show that optical spin and OAM account for the rotation of the polarization and the rotation of the transmitted image, respectively
Chirality and the angular momentum of light
Chirality is exhibited by objects that cannot be rotated into their mirror images. It is far from obvious that this has anything to do with the angular momentum of light, which owes its existence to rotational symmetries. There is nevertheless a subtle connection between chirality and the angular momentum of light. We demonstrate this connection and, in particular, its significance in the context of chiral lightâmatter interactions
Investigations of the Anisotropic Optical Reflectivity of Binary and Ternary Nb-W Oxides Possessing Block-Type Crystal Structure
We have studied the anisotropic optical properties of binary NbO2.5-ÎŽ (0 8) in the infinite block direction only
Genomic organization, expression analysis, and chromosomal localization of the mouse PEX3 gene encoding a peroxisomal assembly protein
The peroxin Pex3p has been identified as an integral peroxisomal membrane protein in yeast where pex3 mutants lack peroxisomal remnant structures. Although not proven in higher organisms, a role of this gene in the early peroxisome biogenesis is suggested, We report here the cDNA cloning and the genomic structure of the mouse PEX3 gene. The 2 kb cDNA encodes a polypeptide of 372 amino acids (42 kDa). The gene spans a region of 30 kb, contains 12 exons and 11 introns and is located on band A of chromosome 10, The putative promoter region exhibits characteristic housekeeping features. PEX3 expression was identified in all tissues analyzed, with the strongest signals in liver and in testis, and could not be induced by fenofibrate. The data presented may be useful for the generation of a mouse model defective in PEX3 in order to clarify the yet unknown functional impact of disturbances in early peroxisomal membrane assembly
A quantum inspired approach to learning dynamical laws from dataâblock-sparsity and gauge-mediated weight sharing
Recent years have witnessed an increased interest in recovering dynamical laws of complex systems in a largely data-driven fashion under meaningful hypotheses. In this work, we propose a scalable and numerically robust method for this task, utilizing efficient block-sparse tensor train representations of dynamical laws, inspired by similar approaches in quantum many-body systems. Low-rank tensor train representations have been previously derived for dynamical laws of one-dimensional systems. We extend this result to efficient representations of systems with K-mode interactions and controlled approximations of systems with decaying interactions. We further argue that natural structure assumptions on dynamical laws, such as bounded polynomial degrees, can be exploited in the form of block-sparse support patterns of tensor-train cores. Additional structural similarities between interactions of certain modes can be accounted for by weight sharing within the ansatz. To make use of these structure assumptions, we propose a novel optimization algorithm, block-sparsity restricted alternating least squares with gauge-mediated weight sharing. The algorithm is inspired by similar notions in machine learning and achieves a significant improvement in performance over previous approaches. We demonstrate the performance of the method numerically on three one-dimensional systemsâthe FermiâPastaâUlamâTsingou system, rotating magnetic dipoles and point particles interacting via modified LennardâJones potentials, observing a highly accurate and noise-robust recovery
Block sparsity and gauge mediated weight sharing for learning dynamical laws from data
Recent years have witnessed an increased interest in recovering dynamical
laws of complex systems in a largely data-driven fashion under meaningful
hypotheses. In this work, we propose a method for scalably learning dynamical
laws of classical dynamical systems from data. As a novel ingredient, to
achieve an efficient scaling with the system size, block sparse tensor trains -
instances of tensor networks applied to function dictionaries - are used and
the self similarity of the problem is exploited. For the latter, we propose an
approach of gauge mediated weight sharing, inspired by notions of machine
learning, which significantly improves performance over previous approaches.
The practical performance of the method is demonstrated numerically on three
one-dimensional systems - the Fermi-Pasta-Ulam-Tsingou system, rotating
magnetic dipoles and classical particles interacting via modified Lennard-Jones
potentials. We highlight the ability of the method to recover these systems,
requiring 1400 samples to recover the 50 particle Fermi-Pasta-Ulam-Tsingou
system to residuum of , 900 samples to recover the 50 particle
magnetic dipole chain to residuum of and 7000 samples to
recover the Lennard-Jones system of 10 particles to residuum
. The robustness against additive Gaussian noise is
demonstrated for the magnetic dipole system.Comment: 13 pages, 6 figure
Chiral rotational spectroscopy
We introduce chiral rotational spectroscopy, a technique that enables the determination of the orientated optical activity pseudotensor components , and of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample and provides an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral solely by virtue of their isotopic constitution and molecules with multiple chiral centers. A basic design for a chiral rotational spectrometer together with a model of its functionality is given. Our proposed technique offers the more familiar polarizability components , and as by-products, which could see it find use even for achiral molecules
Orientated molecular information from chiral rotational spectroscopy
We present details on how the newly introduced technique of chiral rotational spectroscopy can be used to extract orientated information from otherwise freely rotating molecules in the gas phase. In this technique circularly polarized light is used to illuminate chiral molecules and shift their rotational levels to yield orientated chiroptical information via their rotational spectrum. This enables in particular the determination of the individual, physically relevant components of the orientated optical activity pseudotensor. Using the explicit example of (S)-propylene glycol we show how measuring the rotational spectrum of molecules in the microwave domain allows for the recording of a small set of rotational transitions from which the individual polarizability components can be determined
Switching Behaviour of a Series Connection of a Vacuum Interrupter and a Gas Circuit Breaker
After being in the focus of sciences' and industry's research and development activities for many years, the investigation of possible SF6 gas-alternatives has been even more intensified after the revision of the European F-Gas regulation 517/2014. As natural gases yield a significantly lower dielectric strength in comparison to SF6, new challenges arise for the design of high voltage switchgear. Vacuum interrupters are environmentally friendly, reliable and able to withstand steep rising transient recovery voltages. In the last years, first installations of switchgear based on vacuum switching technology in sub-transmission level are in operation. One option for the realization of a SF6 free high voltage switchgear for transmission level is the combination of a gas circuit breaker filled with an atmospheric gas with a vacuum interrupter in a hybrid switchgear. In this contribution the voltage distribution and switching behavior of a hybrid circuit breaker is experimentally investigated
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