11,078 research outputs found
Exciton trapping in magnetic wire structures
The lateral magnetic confinement of quasi two-dimensional excitons into wire
like structures is studied. Spin effects are take into account and two
different magnetic field profiles are considered, which experimentally can be
created by the deposition of a ferromagnetic stripe on a semiconductor quantum
well with magnetization parallel or perpendicular to the grown direction of the
well. We find that it is possible to confine excitons into one-dimensional (1D)
traps. We show that the dependence of the confinement energy on the exciton
wave vector, which is related to its free direction of motion along the wire
direction, is very small. Through the application of a background magnetic
field it is possible to move the position of the trapping region towards the
edge of the ferromagnetic stripe or even underneath the stripe. The exact
position of this 1D exciton channel depends on the strength of the background
magnetic field and on the magnetic polarisation direction of the ferromagnetic
film.Comment: 10 pages, 7 figures, to be published in J. Phys: Condens. Matte
The role of dissipation in biasing the vacuum selection in quantum field theory at finite temperature
We study the symmetry breaking pattern of an O(4) symmetric model of scalar
fields, with both charged and neutral fields, interacting with a photon bath.
Nagasawa and Brandenberger argued that in favourable circumstances the vacuum
manifold would be reduced from S^3 to S^1. Here it is shown that a selective
condensation of the neutral fields, that are not directly coupled to photons,
can be achieved in the presence of a minimal ``external'' dissipation, i.e. not
related to interactions with a bath. This should be relevant in the early
universe or in heavy-ion collisions where dissipation occurs due to expansion.Comment: Final version to appear in Phys. Rev. D, 2 figures added, 2 new
sub-section
Constraining the relative inclinations of the planets B and C of the millisecond pulsar PSR B1257+12
We investigate on the relative inclination of the planets B and C orbiting
the pulsar PSR B1257+12 in connection with potential violations of the
equivalence principle (Abridged).Comment: LaTex2e, 10 pages, 1 table, 3 figures, 17 references. Small stylistic
changes. Version to appear in Journal of Astrophysics and Astronomy (JAA
Antonio Gramsci’s impact on critical pedagogy
This paper provides an account of Antonio Gramsci’s impact on the area of critical pedagogy. It indicates the Gramscian influence on the thinking of major exponents of the field. It foregrounds Gramsci's ideas and then indicates how they have been taken up by a selection of critical pedagogy exponents who were chosen on the strength of their identification and engagement with Gramsci's ideas, some of them even having written entire essays on Gramsci. The essay concludes with a discussion concerning an aspect of Gramsci's concerns, the question of powerful knowledge, which, in the present author's view, provides a formidable challenge to critical pedagogues.peer-reviewe
The Role of Cytoplasmic mRNA Cap-Binding Protein Complexes in Trypanosoma brucei and Other Trypanosomatids.
Trypanosomatid protozoa are unusual eukaryotes that are well known for having unusual ways of controlling their gene expression. The lack of a refined mode of transcriptional control in these organisms is compensated by several post-transcriptional control mechanisms, such as control of mRNA turnover and selection of mRNA for translation, that may modulate protein synthesis in response to several environmental conditions found in different hosts. In other eukaryotes, selection of mRNA for translation is mediated by the complex eIF4F, a heterotrimeric protein complex composed by the subunits eIF4E, eIF4G, and eIF4A, where the eIF4E binds to the 5'-cap structure of mature mRNAs. In this review, we present and discuss the characteristics of six trypanosomatid eIF4E homologs and their associated proteins that form multiple eIF4F complexes. The existence of multiple eIF4F complexes in trypanosomatids evokes exquisite mechanisms for differential mRNA recognition for translation
- …