23,196 research outputs found
Relativistic charged fluid flow. III - Generalized Hamilton-Jacobi equation
Generalized Hamilton-Jacobi equation and Clebsch transform applied to relativistic plasma flo
Influence of clamp-widening on the quality factor of nanomechanical silicon nitride resonators
Nanomechanical resonators based on strained silicon nitride (SiN)
have received a large amount of attention in fields such as sensing and quantum
optomechanics due to their exceptionally high quality factors (s).
Room-temperature s approaching 1 billion are now in reach by means of
phononic crystals (soft-clamping) and strain engineering. Despite great
progress in enhancing s, difficulties in fabrication of soft-clamped samples
limits their implementation into actual devices. An alternative means of
achieving ultra-high s was shown using trampoline resonators with engineered
clamps, which serves to localize the stress to the center of the resonator,
while minimizing stress at the clamping. The effectiveness of this approach has
since come into question from recent studies employing string resonators with
clamp-tapering. Here, we investigate this idea using nanomechanical string
resonators with engineered clampings similar to those presented for
trampolines. Importantly, the effect of orienting the strings diagonally or
perpendicularly with respect to the silicon frame is investigated. It is found
that increasing the clamp width for diagonal strings slightly increases the
s of the fundamental out-of-plane mode at small radii, while perpendicular
strings only deteriorate with increasing clamp width. Measured s agree well
with finite element method simulations even for higher-order resonances. The
small increase cannot account for previously reported s of trampoline
resonators. Instead, we propose the effect to be intrinsic and related to
surface and radiation losses.Comment: 7 pages, 4 figure
Spinor solution of the sound wave problem
Spinor solution of sound wave in electrically neutral ga
Multi-qubit entanglement engineering via projective measurements
So far, various multi-photon entangled states have been observed
experimentally by using different experimental set-ups. Here, we present a
scheme to realize many SLOCC-inequivalent states of three and four qubits via
projective measurements on suitable entangled states. We demonstrate how these
states can be observed experimentally in a single set-up and study the
feasibility of the implementation with present-day technology
Metaspin and dirishonic dark matter
The antisymmetry requirement of rishon bound state wave functions suggests a
new rishon quantum number called M spin. From M spin conservation and the
Nussinov-Weingarten-Witten theorem we predict the existence of a stable
pseudoscalar dirishonic meson, called zeta, that is lighter than the lightest
neutrino. Its mass is estimated as m(zeta) = 10^{-9} eV. This particle could
make up the major part of cold dark matter in the Universe.Comment: 8 pages, 1 figur
Evaluation and registration of plant protection inputs for organic farming
Organic farmers may only use those plant protection products which are listed in Annex II B of the ‘Organic Regulation’ 2092/91 and also registered for use at national level. At present, new compounds may only be listed in Reg. 2092/91, if they do not come into direct contact with the crop (although in perennial crops, contact outside the growing season of the edible parts is possible), which is a major obstacle for progress. The EU-funded ORGANIC INPUTS EVALUATION project aims at making Reg. 2092/91 more flexible with regard to new products, while safeguarding the principles of organic farming. Registra-tion under the ‘Pesticide Directive’ 91/414 represents a considerable financial hurdle. The REBECA project will propose registration requirements which are better adapted for biological control agents, plant extracts and other low-risk products. The aim is to accelerate registration and make it more cost-effective, without compromises to the level of safety
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