343 research outputs found
On Chromospheric Variations Modeling for Main-Sequence Stars of G and K Spectral Classes
We present a method of chromospheric flux simulation for 13 late-type
main-sequence stars. These Sun-like stars have well-determined cyclic flux
variations similar to 11 yr solar activity cycle. Our flux prediction is based
on chromospheric HK emission time series measurements from Mount Wilson
Observatory and comparable solar data. We show that solar three - component
modeling explains well the stellar observations. We find that the 10 - 20% of K
- stars disc surfaces are occupied by bright active regions.Comment: 8 pages, 2 figure
Quantum phase transitions in a new exactly solvable quantum spin biaxial model with multiple spin interactions
The new integrable quantum spin model is proposed. The model has a biaxial
magnetic anisotropy of alternating coupling between spins together with
multiple spin interactions. Our model gives the possibility to exactly find
thermodynamic characteristics of the considered spin chain. The ground state of
the model can reveal spontaneous values of the total magnetic and
antiferromagnetic moments, caused by multiple spin couplings. Also, in the
ground state, depending on the strength of multiple spin couplings, our model
manifests several quantum critical points, some of which are governed by the
external magnetic field
Stable Spin Precession at one Half of Equilibrium Magnetization in Superfluid 3He-B
New stable modes of spin precession have been observed in superfluid 3He-B.
These dynamical order parameter states include precession with a magnetization
S=pS_{eq} which is different from the equilibrium value S_{eq}. We have
identified modes with p=1, 1/2 and \approx 0. The p=1/2 mode is the second
member of phase correlated states of a spin superfluid. The new states can be
excited in the temperature range 1-T/T_c \lesssim 0.02 where the energy
barriers between the different local minima of the spin-orbit energy are small.
They are stable in CW NMR due to low dissipation close to T_c.Comment: submitted to Physical Review Letters, 4 pages, revtex, 4 Figures in
ftp://boojum.hut.fi/pub/publications/lowtemp/LTL-96005.p
Methodological aspects of the use of dry components of chicken eggs for feeding children with phenylketonuria
Currently, one of the most important tasks facing science and production is the creation of functional product technologies for use in different diets of the population in order to preserve and improve health, as well as reduce the risks and consequences of various diseases, including hereditary ones, such as phenylketonuria (PKU). The All-Russian Research Institute of Starch Products develops technologies for the production of low-protein starch-based products/semi-products enriched with functional ingredients and intended for therapeutic nutrition of patients with PKU. As part of the pilot production, the production of these products is organized. Purpose of work:to justify the possibility of using dry components of chicken eggs (melange, protein, yolk) to enrich low-protein starch products (noodles, vermichel, «spider») intended for feeding children over 3 years old with phenylketonuria;evaluate organoleptic properties and efficiency of low-protein starch products enriched in hypophenylalanine diet of patients with phenylketonuria older than 3 years
Phonons in magnon superfluid and symmetry breaking field
Recent experiments [1],[2] which measured the spectrum of the Goldstone
collective mode of coherently precessing state in 3He-B are discussed using the
presentation of the coherent spin precession in terms of the Bose-Einstein
condensation of magnons. The mass in the spectrum of the Goldstone boson --
phonon in the superfluid magnon liquid -- is induced by the symmetry breaking
field, which is played by the RF magnetic fieldComment: 2 pages, JETP Letters style, no figures, version accepted in JETP
Letter
Solution of the problem of catastrophic relaxation of homogeneous spin precession in superfluid He-B
The quantitative analysis of the "catastrophic relaxation" of the coherent
spin precession in He-B is presented. This phenomenon has been observed
below the temperature about 0.5 T as an abrupt shortening of the induction
signal decay. It is explained in terms of the decay instability of homogeneous
transverse NMR mode into spin waves of the longitudinal NMR. Recently the cross
interaction amplitude between the two modes has been calculated by Sourovtsev
and Fomin \cite{SF} for the so-called Brinkman-Smith configuration, i.e. for
the orientation of the orbital momentum of Cooper pairs along the magnetic
field, . In their treatment, the interaction is
caused by the anisotropy of the speed of the spin waves. We found that in the
more general case of the non-parallel orientation of corresponding to
the typical conditions of experiment, the spin-orbital interaction provides the
additional interaction between the modes. By analyzing experimental data we are
able to distinguish which contribution is dominating in different regimes.Comment: 6 pages, 1 figure, submited to JETP letter
Magnon BEC in superfluid 3He-A
The new mode of magnetization precession in superfluid 3He-A in a squeezed
aerogel has been recently reported. We consider this mode in terms of the
Bose-Einstein condensation (BEC) of magnons. The difference between magnon BEC
states in 3He-A and in 3He-B is discussed.Comment: 6 pages, 2 figures, JETP Letters style, published versio
The ionization of Mg by electron impact at 1000 eV studied by (e, 2e) experiments
The ionization of Mg 3s and 2p and He 1s has been studied in (e, 2e) experiments at about 1000 eV incident energy and 20 eV ejected electron energy for a momentum transfer between 0.5 and 2.1 au. The comparison with the predictions of the distorted wave Born approximation model shows a generally good agreement between experiment and theory. The differences observed between the He and Mg angular distributions can be explained as an initial state effect and are attributed to the differences between the He 1s and Mg 3s wavefunctions in the momentum space
Quantum analogue of the spin-flop transition for a spin pair
Quantum (step-like) magnetization curves are studies for a spin pair with
antiferromagnetic coupling in the presence of a magnetic field parallel to the
easy axis of the magnetic anisotropy. The consideration is done both
analytically and numerically for a wide range of the anisotropy constants and
spins up to . Depending on the origin of the anisotropy
(exchange or single-ion), the magnetization curve can demonstrate the jumps
more than unity and the concentration of the unit jumps in a narrow range of
the field. We also point the region of the problem parameters, where the
behavior is quasiclassical for , and where system is substantially
quantum in the limit .Comment: 5 pages, 5 figure
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