213 research outputs found
Spectrum of bound fermion states on vortices in He-B
We study subgap spectra of fermions localized within vortex cores in
He-B. We develop an analytical treatment of the low-energy states and
consider the characteristic properties of fermion spectra for different types
of vortices. Due to the removed spin degeneracy the spectra of all singly
quantized vortices consist of two different anomalous branches crossing the
Fermi level. For singular and vortices the anomalous branches are
similar to the standard Caroli-de Gennes -Matricon ones and intersect the Fermi
level at zero angular momentum yet with different slopes corresponding to
different spin states. On the contrary the spectral branches of nonsingular
vortices intersect the Fermi level at finite angular momenta which leads to the
appearance of a large number of zero modes, i.e. energy states at the Fermi
level. Considering the , and vortices with superfluid cores we
show that the number of zero modes is proportional to the size of the vortex
core.Comment: 6 pages, 1 figur
Nanocellulose: Recent Fundamental Advances and Emerging Biological and Biomimicking Applications
In the e'ort toward sustainable advanced functional materials, nanocellu- loses have attracted extensive recent attention. Nanocelluloses range from rod-like highly crystalline cellulose nanocrystals to longer and more entan- gled cellulose nanofibers, earlier denoted also as microfibrillated celluloses and bacterial cellulose. In recent years, they have spurred research toward a wide range of applications, ranging from nanocomposites, viscosity modi- fiers, films, barrier layers, fibers, structural color, gels, aerogels and foams, and energy applications, until filtering membranes, to name a few. Still, nanocelluloses continue to show surprisingly high challenges to master their interactions and tailorability to allow well-controlled assemblies for functional materials. Rather than trying to review the already extensive nanocellulose literature at large, here selected aspects of the recent progress are the focus. Water interactions, which are central for processing for the functional proper- ties, are discussed first. Then advanced hybrid gels toward (multi)stimuli responses, shape-memory materials, self-healing, adhesion and gluing, bio- logical sca'olding, and forensic applications are discussed. Finally, composite fibers are discussed, as well as nanocellulose as a strategy for improvement of photosynthesis-based chemicals production. In summary, selected per- spectives toward new directions for sustainable high-tech functional mate- rials science based on nanocelluloses are described. </div
NMR Experiments on Rotating Superfluid 3He-A : Evidence for Vorticity
Experiments on rotating superfluid 3He-A in an open cylindrical geometry show a change in the NMR line shape as a result of rotation: The amplitude of the peak decreases in proportion to f(T)g(Ω), where Ω is the angular velocity of rotation; at the same time the line broadens. Near Tc, f(T) is a linear function of 1−T/Tc. At small velocities g(Ω)∝Ω. These observations are consistent with the existence of vortices in rotating 3He-A.Peer reviewe
Self-assembly in solution of a reversible comb-shaped supramolecular polymer
We report a single step synthesis of a polyisobutene with a bis-urea moiety
in the middle of the chain. In low polarity solvents, this polymer
self-assembles by hydrogen bonding to form a combshaped polymer with a central
hydrogen bonded backbone and polyisobutene arms. The comb backbone can be
reversibly broken, and consequently, its length can be tuned by changing the
solvent, the concentration or the temperature. Moreover, we have proved that
the bulkiness of the side-chains have a strong influence on both the
self-assembly pattern and the length of the backbone. Finally, the density of
arms can be reduced, by simply mixing with a low molar mass bis-urea
Self-Assembly of Supramolecular Triblock Copolymer Complexes
Four different poly(tert-butoxystyrene)-b-polystyrene-b-poly(4-vinylpyridine) (PtBOS-b-PS-b-P4VP) linear triblock copolymers, with the P4VP weight fraction varying from 0.08 to 0.39, were synthesized via sequential anionic polymerization. The values of the unknown interaction parameters between styrene and tert-butoxystyrene and between tert-butoxystyrene and 4-vinylpyridine were determined from random copolymer blend miscibility studies and found to satisfy 0.031<χS,tBOS<0.034 and 0.39<χ4VP,tBOS<0.43, the latter being slightly larger than the known 0.30<χS,4VP≤0.35 value range. All triblock copolymers synthesized adopted a P4VP/PS core/shell cylindrical self-assembled morphology. From these four triblock copolymers supramolecular complexes were prepared by hydrogen bonding a stoichiometric amount of pentadecylphenol (PDP) to the P4VP blocks. Three of these complexes formed a triple lamellar ordered state with additional short length scale ordering inside the P4VP(PDP) layers. The self-assembled state of the supramolecular complex based on the triblock copolymer with the largest fraction of P4VP consisted of alternating layers of PtBOS and P4VP(PDP) layers with PS cylinders inside the latter layers. The difference in morphology between the triblock copolymers and the supramolecular complexes is due to two effects: (i) a change in effective composition and, (ii) a reduction in interfacial tension between the PS and P4VP containing domains. The small angle X-ray scattering patterns of the supramolecules systems are very temperature sensitive. A striking feature is the disappearance of the first order scattering peak of the triple lamellar state in certain temperature intervals, while the higher order peaks (including the third order) remain. This is argued to be due to the thermal sensitivity of the hydrogen bonding and thus directly related to the very nature of these systems.
Self-Assembled Poly(4-vinylpyridine)−Surfactant Systems Using Alkyl and Alkoxy Phenylazophenols
Improving Brush Polymer Infrared One-Dimensional Photonic Crystals via Linear Polymer Additives
Phase Behavior of Complementary Multiply Hydrogen Bonded End-Functional Polymer Blends
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