965 research outputs found
Knowledge about AIDS among medical students in Iran
Young people are among the high risk group who are susceptible to sexually transmitted diseases. Several educational programs are scheduled to raise awareness about risky behaviours and to decrease the rate of the HIV pandemic. This cross sectional study showed that in young medical students, the level of awareness about HIV/AIDS increased during the years of academic education (not significant) and that males have a higher level of awareness than females. Higher awareness is desirable in this group due to their key role in the community
The atomic structure of ultrathin oxide films and interfaces studied by surface X-ray diffraction
X-ray diffraction (XRD) studies of the atomic structure of ultrathin oxide films and interfaces are presented, which are conducted within the framework of the Sonderforschungsbereich 762 (functionality of oxide interfaces). Knowledge of the atomic structure is at the heart of the study of functional oxides. XRD allows the investigation of complex systems frequently encountered in oxide systems (large unit cells, complex relaxation patterns, and structural and chemical disorder). Results are combined with first-principles calculations and complementary techniques providing a thorough understanding of the oxides' functionality. The structure analysis of the approximant (AP) to the 2D oxidic quasicrystal (QC) based on BaTiO3 (BTO) is discussed, the first oxide-type QC discovered. This AP is related to the Kepler tiling described 400 years ago. The LaFeO3/SrTiO3 interface is examined, which is a prototype for the formation of a 2D electron gas (2DEG). Subtle interfacial chemical roughness in combination with oxygen off-stoichiometry strongly influences the critical LaFeO3 thickness for the 2DEG formation. Finally, the analysis of the multiferroic BTO/ME(001) (ME = Fe, Pd, Pt) interface reveals that a submonolayer of impurities is the origin for the inversion of the BTO film/vacuum termination from BaO on Fe(001) to TiO2 on Pt(001)
A three-dimensional momentum-space calculation of three-body bound state in a relativistic Faddeev scheme
In this paper, we study the relativistic effects in a three-body bound state.
For this purpose, the relativistic form of the Faddeev equations is solved in
momentum space as a function of the Jacobi momentum vectors without using a
partial wave decomposition. The inputs for the three-dimensional Faddeev
integral equation are the off-shell boost two-body matrices, which are
calculated directly from the boost two-body interactions by solving the
Lippmann-Schwinger equation. The matrix elements of the boost interactions are
obtained from the nonrelativistic interactions by solving a nonlinear integral
equation using an iterative scheme. The relativistic effects on three-body
binding energy are calculated for the Malfliet-Tjon potential. Our calculations
show that the relativistic effects lead to a roughly 2\% reduction in the
three-body binding energy. The contribution of different Faddeev components in
the normalization of the relativistic three-body wave function is studied in
detail. The accuracy of our numerical solutions is tested by calculation of the
expectation value of the three-body mass operator, which shows an excellent
agreement with the relativistic energy eigenvalue
On the motion of spinning test particles in plane gravitational waves
The Mathisson-Papapetrou-Dixon equations for a massive spinning test particle
in plane gravitational waves are analysed and explicit solutions constructed in
terms of solutions of certain linear ordinary differential equations. For
harmonic waves this system reduces to a single equation of Mathieu-Hill type.
In this case spinning particles may exhibit parametric excitation by
gravitational fields. For a spinning test particle scattered by a gravitational
wave pulse, the final energy-momentum of the particle may be related to the
width, height, polarisation of the wave and spin orientation of the particle.Comment: 11 page
A Regularization of Burgers Equation using a Filtered Convective Velocity
This paper examines the properties of a regularization of Burgers equation in
one and multiple dimensions using a filtered convective velocity, which we have
dubbed as convectively filtered Burgers (CFB) equation. A physical motivation
behind the filtering technique is presented. An existence and uniqueness
theorem for multiple dimensions and a general class of filters is proven.
Multiple invariants of motion are found for the CFB equation and are compared
with those found in viscous and inviscid Burgers equation. Traveling wave
solutions are found for a general class of filters and are shown to converge to
weak solutions of inviscid Burgers equation with the correct wave speed.
Accurate numerical simulations are conducted in 1D and 2D cases where the shock
behavior, shock thickness, and kinetic energy decay are examined. Energy
spectrum are also examined and are shown to be related to the smoothness of the
solutions
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