170 research outputs found
Educating and training in an Ideological vacuum: A critical explanation of the dilemma of education in Zimbabwe
This paper is a philosophical study on ideology and its indispensable relationship to education policy making and implementation and its didactical dimension with a special reference to Zimbabwe. The paper points out that successive colonial governments and religious organisations of that era established and worked, planned and implemented their policies within the bounds of liberal-cum-capitalist ideological framework. Hence all their education and training institutions were built and meant to fulfill that cause. Post-independent Africa inherited that framework and found herself giving her citizens education that created useless school leavers. This paper will advance an argument that educating and training in an ideological vacuum stifles critical and creative thinking which is the sources and foundation of potential invention and innovation. It therefore calls for Africa to come up with an ideological framework that defines their contextual social, political, and economic condition(s) resulting in crafting policies that are relevant to their needs than repeating tired ideologies. Key words: Ideology, education, training, vacuum, Zimbabwe, society
An exploration of ebook selection behavior in academic library collections
Academic libraries have offered ebooks for some time, however little is known about how readers interact with them while making relevance decisions. In this paper we seek to address that gap by analyzing ebook transaction logs for books in a university library
Sum rules and energy scales in the high-temperature superconductor YBa2Cu3O6+x
The Ferrell-Glover-Tinkham (FGT) sum rule has been applied to the temperature
dependence of the in-plane optical conductivity of optimally-doped
YBa_2Cu_3O_{6.95} and underdoped YBa_2Cu_3O_{6.60}. Within the accuracy of the
experiment, the sum rule is obeyed in both materials. However, the energy scale
\omega_c required to recover the full strength of the superfluid \rho_s in the
two materials is dramatically different; \omega_c \simeq 800 cm^{-1} in the
optimally doped system (close to twice the maximum of the superconducting gap,
2\Delta_0), but \omega_c \gtrsim 5000 cm^{-1} in the underdoped system. In both
materials, the normal-state scattering rate close to the critical temperature
is small, \Gamma < 2\Delta_0, so that the materials are not in the dirty limit
and the relevant energy scale for \rho_s in a BCS material should be twice the
energy gap. The FGT sum rule in the optimally-doped material suggests that the
majority of the spectral weight of the condensate comes from energies below
2\Delta_0, which is consistent with a BCS material in which the condensate
originates from a Fermi liquid normal state. In the underdoped material the
larger energy scale may be a result of the non-Fermi liquid nature of the
normal state. The dramatically different energy scales suggest that the nature
of the normal state creates specific conditions for observing the different
aspects of what is presumably a central mechanism for superconductivity in
these materials.Comment: RevTeX 4 file, 9 pages with 7 embedded eps figure
S and D Wave Mixing in High Superconductors
For a tight binding model with nearest neighbour attraction and a small
orthorhombic distortion, we find a phase diagram for the gap at zero
temperature which includes three distinct regions as a function of filling. In
the first, the gap is a mixture of mainly -wave with a smaller extended
-wave part. This is followed by a region in which there is a rapid increase
in the -wave part accompanied by a rapid increase in relative phase between
and from 0 to . Finally, there is a region of dominant with a
mixture of and zero phase. In the mixed region with a finite phase, the
-wave part of the gap can show a sudden increase with decreasing temperature
accompanied with a rapid increase in phase which shows many of the
characteristics measured in the angular resolved photoemission experiments of
Ma {\em et al.} in Comment: 12 pages, RevTeX 3.0, 3 PostScript figures uuencoded and compresse
Glimpses of the Octonions and Quaternions History and Todays Applications in Quantum Physics
Before we dive into the accessibility stream of nowadays indicatory
applications of octonions to computer and other sciences and to quantum physics
let us focus for a while on the crucially relevant events for todays revival on
interest to nonassociativity. Our reflections keep wandering back to the
two square identity and then via the four
square identity up to the eight square identity.
These glimpses of history incline and invite us to retell the story on how
about one month after quaternions have been carved on the bridge
octonions were discovered by , jurist and
mathematician, a friend of . As for today we just
mention en passant quaternionic and octonionic quantum mechanics,
generalization of equations for octonions and triality
principle and group in spinor language in a descriptive way in order not
to daunt non specialists. Relation to finite geometries is recalled and the
links to the 7stones of seven sphere, seven imaginary octonions units in out of
the cave reality applications are appointed . This way we are welcomed
back to primary ideas of , and other distinguished
fathers of quantum mechanics and quantum gravity foundations.Comment: 26 pages, 7 figure
Dynamic generation of maximally entangled photon multiplets by adiabatic passage
The adiabatic passage scheme for quantum state synthesis, in which atomic
Zeeman coherences are mapped to photon states in an optical cavity, is extended
to the general case of two degenerate cavity modes with orthogonal
polarization. Analytical calculations of the dressed-state structure and Monte
Carlo wave-function simulations of the system dynamics show that, for a
suitably chosen cavity detuning, it is possible to generate states of photon
multiplets that are maximally entangled in polarization. These states display
nonclassical correlations of the type described by Greenberger, Horne, and
Zeilinger (GHZ). An experimental scheme to realize a GHZ measurement using
coincidence detection of the photons escaping from the cavity is proposed. The
correlations are found to originate in the dynamics of the adiabatic passage
and persist even if cavity decay and GHZ state synthesis compete on the same
time scale. Beyond entangled field states, it is also possible to generate
entanglement between photons and the atom by using a different atomic
transition and initial Zeeman state.Comment: 22 pages (RevTeX), including 23 postscript figures. To be published
in Physical Review
Identification of the bulk pairing symmetry in high-temperature superconductors: Evidence for an extended s-wave with eight line nodes
we identify the intrinsic bulk pairing symmetry for both electron and
hole-doped cuprates from the existing bulk- and nearly bulk-sensitive
experimental results such as magnetic penetration depth, Raman scattering,
single-particle tunneling, Andreev reflection, nonlinear Meissner effect,
neutron scattering, thermal conductivity, specific heat, and angle-resolved
photoemission spectroscopy. These experiments consistently show that the
dominant bulk pairing symmetry in hole-doped cuprates is of extended s-wave
with eight line nodes, and of anisotropic s-wave in electron-doped cuprates.
The proposed pairing symmetries do not contradict some surface- and
phase-sensitive experiments which show a predominant d-wave pairing symmetry at
the degraded surfaces. We also quantitatively explain the phase-sensitive
experiments along the c-axis for both Bi_{2}Sr_{2}CaCu_{2}O_{8+y} and
YBa_{2}Cu_{3}O_{7-y}.Comment: 11 pages, 9 figure
Coupling between planes and chains in YBa2Cu3O7 : a possible solution for the order parameter controversy
We propose to explain the contradictory experimental evidence about the
symmetry of the order parameter in by taking into account
the coupling between planes and chains. This leads to an anticrossing of the
plane and chain band. We include an attractive pairing interaction within the
planes and a repulsive one between planes and chains, leading to opposite signs
for the order parameter on planes and chains, and to nodes of the gap because
of the anticrossing. Our model blends s-wave and d-wave features, and provides
a natural explanation for all the contradictory experimentsComment: 13 pages, revtex, 2 uucoded figure
Single-particle nonlocality and entanglement with the vacuum
We propose a single-particle experiment that is equivalent to the
conventional two-particle experiment used to demonstrate a violation of Bell's
inequalities. Hence, we argue that quantum mechanical nonlocality can be
demonstrated by single-particle states. The validity of such a claim has been
discussed in the literature, but without reaching a clear consensus. We show
that the disagreement can be traced to what part of the total state of the
experiment one assigns to the (macroscopic) measurement apparatus. However,
with a conventional and legitimate interpretation of the measurement process
one is led to the conclusion that even a single particle can show nonlocal
properties.Comment: 6 pages, 5 figure
Anisotropic superconductivity mediated by phonons in layered compounds with weak screening effect
Anisotropic pairing interactions mediated by phonons are examined in layer
systems. It is shown that the screening effects become weaker when the layer
spacing increases. Then the anisotropic components of the pairing interactions
increase with the screening length since the momentum dependence changes. As a
result, various types of anisotropic superconductivity occur depending on the
parameter region. For example, p-wave superconductivity occurs when the
short-range part of Coulomb repulsion is strong and the layer spacing is large.
Two kinds of inter-layer pairing may occur when the layer spacing is not too
large. Although the phonon contribution to the d-wave pairing interaction is
weaker than the p-wave interaction, it increases with the layer spacing.
Relevance of the present results to organic superconductors, high-T_c cuprates,
and Sr_2RuO_4 is discussed.Comment: 8 pages, 5 figures, (Latex, revtex.sty, epsf.sty
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