9,844 research outputs found
New broad 8Be nuclear resonances
Energies, total and partial widths, and reduced width amplitudes of 8Be
resonances up to an excitation energy of 26 MeV are extracted from a coupled
channel analysis of experimental data. The presence of an extremely broad J^pi
= 2^+ ``intruder'' resonance is confirmed, while a new 1^+ and very broad 4^+
resonance are discovered. A previously known 22 MeV 2^+ resonance is likely
resolved into two resonances. The experimental J^pi T = 3^(+)? resonance at 22
MeV is determined to be 3^-0, and the experimental 1^-? (at 19 MeV) and 4^-?
resonances to be isospin 0.Comment: 16 pages, LaTe
Erratum: Post-Newtonian two-body and n-body problems with electric charge in general relativity (Journal of Mathematical Physics (1977) 18 (1818))
An approach to NLO QCD analysis of the semi-inclusive DIS data with modified Jacobi polynomial expansion method
It is proposed the modification of the Jacobi polynomial expansion method
(MJEM) which is based on the application of the truncated moments instead of
the full ones. This allows to reconstruct with a high precision the local quark
helicity distributions even for the narrow accessible for measurement Bjorken
region using as an input only four first moments extracted from the data in
NLO QCD. It is also proposed the variational (extrapolation) procedure allowing
to reconstruct the distributions outside the accessible Bjorken region
using the distributions obtained with MJEM in the accessible region. The
numerical calculations encourage one that the proposed variational
(extrapolation) procedure could be applied to estimate the full first
(especially important) quark moments
Contamination potential of tar sand exploitation in the western Niger-Delta of Nigeria: baseline studies
Exploitation of the tar sands in Ondo State in
the Niger Delta is likely to result in some environmental
contamination and adversely affect the living conditions of
the farmers and fishermen in the area. Three wells were
established where samples were taken at 1, 2 and 3 m
depth. Although no hydrocarbon contamination was
detected in the water from the surface and boreholes, saline
intrusion was recorded. This study produces a baseline
against which future contamination can be monitored so
that preventative measures can be taken to mitigate the
effects
Constrained Monte Carlo Method and Calculation of the Temperature Dependence of Magnetic Anisotropy
We introduce a constrained Monte Carlo method which allows us to traverse the
phase space of a classical spin system while fixing the magnetization
direction. Subsequently we show the method's capability to model the
temperature dependence of magnetic anisotropy, and for bulk uniaxial and cubic
anisotropies we recover the low-temperature Callen-Callen power laws in M. We
also calculate the temperature scaling of the 2-ion anisotropy in L10 FePt, and
recover the experimentally observed M^2.1 scaling. The method is newly applied
to evaluate the temperature dependent effective anisotropy in the presence of
the N'eel surface anisotropy in thin films with different easy axis
configurations. In systems having different surface and bulk easy axes, we show
the capability to model the temperature-induced reorientation transition. The
intrinsic surface anisotropy is found to follow a linear temperature behavior
in a large range of temperatures
Bostonia. Volume 15
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
Gyroscope deviation from geodesic motion: quasiresonant oscillations on a circular orbit
General relativistic spin-orbit interaction leads to the quasiresonant
oscillation of the gyroscope mass center along the orbital normal. The beating
amplitude does not include the speed of light and equals the ratio of the
intrinsic momentum of the gyroscope to its orbital momentum. The modulation
frequency equals the angular velocity of the geodetic precession that prevents
the oscillation from resonance. The oscillation represents the precession of
the gyroscope orbital momentum. Within an acceptable time the oscillation
amplitude reaches the values that are amenable to being analyzed
experimentally. Taking into account the source oblateness decreases the beating
amplitude and increases the modulation frequency by the factor that is equal to
the ratio of the quadrupole precession velocity to the geodetic precession
velocity. The period of the quadrupole precession turns out to be a quite
sufficient time to form a measurable amplitude of the oscillation.Comment: 5 pages, LaTeX2e, 1 eps figure, to appear in J. Exp. Theor. Phy
The Landau-Lifshitz equation in atomistic models
The Landau–Lifshitz (LL) equation, originally proposed at the macrospin level, is increasingly used in Atomistic Spin Dynamic (ASD) models. These models are based on a spin Hamiltonian featuring atomic spins of fixed length, with the exchange introduced using the Heisenberg formalism. ASD models are proving a powerful approach to the fundamental understanding of ultrafast magnetization dynamics, including the prediction of the thermally induced magnetization switching phenomenon in which the magnetization is reversed using an ultra-fast laser pulse in the absence of an externally applied field. This paper outlines the ASD model approach and considers the role and limitations of the LL equation in this context
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