5,302 research outputs found
Linear spin wave theory for single-Q incommensurate magnetic structures
Linear spin wave theory provides the leading term in the calculation of the
excitation spectra of long-range ordered magnetic systems as a function of
. This term is acquired using the Holstein-Primakoff approximation
of the spin operator and valid for small fluctuations of the ordered
moment. We propose an algorithm that allows magnetic ground states with general
moment directions and single-Q incommensurate ordering wave vector using a
local coordinate transformation for every spin and a rotating coordinate
transformation for the incommensurability. Finally we show, how our model can
determine the spin wave spectrum of the magnetic C-site langasites with
incommensurate order.Comment: 12 pages, 3 figures, cite this paper if you use SpinW
(http://www.psi.ch/spinw
The effect of radiation on the long term productivity of a plant based CELSS
Mutations occur at a higher rate in space than under terrestrial conditions, primarily due to an increase in radiation levels. These mutations may effect the productivity of plants found in a controlled ecological life support system (CELSS). Computer simulations of plants with different ploidies, modes of reproduction, lethality thresholds, viability thresholds and susceptibilities to radiation induced mutations were performed under space normal and solar flare conditions. These simulations identified plant characteristics that would enable plants to retain high productivities over time in a CELSS
Investigations of the effect of nonmagnetic Ca substitution for magnetic Dy on spin-freezing in Dy2Ti2O7
Physical properties of partially Ca substituted hole-doped Dy2Ti2O7 have been
investigated by ac magnetic susceptibility \chi_ac(T), dc magnetic
susceptibility \chi(T), isothermal magnetization M(H) and heat capacity C_p(T)
measurements on Dy1.8Ca0.2Ti2O7. The spin-ice system Dy2Ti2O7 exhibits a
spin-glass type freezing behavior near 16 K. Our frequency dependent \chi_ac(T)
data of Dy1.8Ca0.2Ti2O7 show that the spin-freezing behavior is significantly
influenced by Ca substitution. The effect of partial nonmagnetic Ca2+
substitution for magnetic Dy3+ is similar to the previous study on nonmagnetic
isovalent Y3+ substituted Dy2-xYxTi2O7 (for low levels of dilution), however
the suppression of spin-freezing behavior is substantially stronger for Ca than
Y. The Cole-Cole plot analysis reveals semicircular character and a single
relaxation mode in Dy1.8Ca0.2Ti2O7 as for Dy2Ti2O7. No noticeable change in the
insulating behavior of Dy2Ti2O7 results from the holes produced by 10% Ca2+
substitution for Dy3+ ions.Comment: 9 pages, 7 figures, 1 tabl
Magnetic correlations of the quasi-one-dimensional half-integer spin-chain antiferromagnets SrVO ( = Co, Mn)
Magnetic correlations of two iso-structural quasi-one-dimensional (1D)
antiferromagnetic spin-chain compounds SrVO ( = Co, Mn) have
been investigated by magnetization and powder neutron diffraction. Two
different collinear antiferromagnetic (AFM) structures, characterized by the
propagation vectors, = (0 0 1) and = (0 0 0), have been found below
5.2 K and 42.2 K for the Co- and Mn-compounds, respectively. For
the Mn-compound, AFM chains (along the axis) order ferromagnetically within
the plane, whereas, for the Co-compound, AFM chains order
ferro-/antiferromagnetically along the direction. The critical exponent
study confirms that the Co- and Mn-compounds belong to the Ising and Heisenberg
universality classes, respectively. For both compounds, short-range spin-spin
correlations are present over a wide temperature range above . The reduced
ordered moments at base temperature (1.5 K) indicate the presence of quantum
fluctuations in both compounds due to the quasi-1D magnetic interactions.Comment: 14 pages, 10 figures, 9 table
Restraining False Light: Constitutional and Common Law Limits on a Troublesome Tort
The defamation tort is the common law\u27s established remedy for false speech that causes reputational and emotional injury. That tort is subject to intricate constitutional, legislative, and common law rules that have evolved over decades. The false light invasion of privacy tort also provides a potential cause of action in response to injurious falsehood. False light, however, has been subject to much less judicial and legislative scrutiny than defamation. As a result, courts often are uncertain about the proper limits on false light and, in some cases, have countenanced false light claims that would have failed if filed as defamation claims. Allowing such claims conflicts with two important legal principles: (1) the common law principle disfavoring novel causes of action that duplicate established torts, and (2) the constitutional rule of Hustler Magazine v. Falwell. These important legal principles require that courts reject false light claims that challenge defamatory speech but fail to meet defamation law\u27s standards
Water Needs for the Future (By Ved P. Nanda)
Although the importance of water as a natural resource has long been recognized in the arid Western states and in the Middle East, recent disastrous droughts in the African Sahel region, and the United Kingdom have focused worldwide attention on the fact that inadequate supplies of water are a major international problem. Indeed, the specter of a water crisis akin to the much discussed energy crisis has been raised, with a warning from the U.S. Secretary of the Interior of possible cutbacks in residential construction and a decline in the quality of drinking water by the late 1980\u27s.
Water Needs for the Future, which is a refinement of a series of papers presented at the University of Denver College of Law in late 1976, admirably serves the dual purposes of presenting the scope of the problem, and describing the current legal, economic and technological factors which must be considered to formulate a national and international water policy
- …