24,976 research outputs found
Proton Stability In Supersymmetric SU(5)
Within supersymmetric SU(5) GUT we suggest mechanisms for suppression of
baryon number violating dimension five and six operators. The mechanism is
based on the idea of split multiplets (i.e. quarks and leptons are not coming
from a single GUT state) which is realized by an extension with additional
vector-like matter. The construction naturally avoids wrong asymptotic relation
. Thus, the long standing problems of the minimal SUSY
SU(5) GUT can be resolved.
In a particular example of flavor structure and with additional {\cal
U}(1)\tm {\cal Z}_{3N} symmetry we demonstrate how the split multiplet
mechanism works out. Namely, the considered model is compatible with successful
gauge coupling unification and realistic fermion mass pattern. The nucleon
decay rates are relatively suppressed and can be well compatible with current
experimental bounds.Comment: Discussions and some clarifications adde
A model for vortex formation in magnetic nanodots
We use Monte Carlo simulation to study the vortex nucleation on magnetic
nanodots at low temperature. In our simulations, we have considered a simple
microscopic two-dimensional anisotropic Heisenberg model with term to describe
the anisotropy due to the presence of the nanodot edge. We have considered the
thickness of the edge, which was not considered in previous works, introducing
a term that controls the energy associated to the edge. Our results clearly
show that the thickness of the edge has a considerable influence in the vortex
nucleation on magnetic nanodots. We have obtained the hysteresis curve for
several values of the surface anisotropy and skin depth parameter (). The
results are in excellent agreement with experimental data
B cell epitopes in fish nodavirus
Three epitope-mapping procedures were used to identify B-cell epitopes on Betanodaviruses: neutralisation escape mutant sequence analysis, phage display, and pepscan. Betanodaviruses have emerged as major pathogens of marine fish. These viruses are the aetiological agents of a disease referred to as viral nervous necrosis (VNN), which affects many species of fish that are economically valuable to the aquaculture industry. The identification of betanodavirus B-cell epitopes will facilitate the rational development of vaccines to counter VNN.
A panel of mouse monoclonal antibodies (MAbs) was produced using hybridoma methodology for use in each of the epitope mapping procedures. These antibodies were characterised in Western blotting, ELISA, and virus neutralisation tests. Rabbit polyclonal sera, and serum samples from nodavirus-infected fish were also used for pepscan analyses.
Attempts to produce betanodavirus neutralisation escape mutants, using plaque assay or limiting dilution based methods, were not successful.
Two phage libraries expressing random peptides of seven (Ph.D.7â„¢) or twelve (Ph.D.12â„¢) amino acids in length as fusions to the coat protein were used to identify the ligands recognised by MAbs directed against betanodavirus. Neither of these phage libraries yielded conclusive results. Phage clones containing tandem inserts were obtained after MAb selection from library Ph.D.7â„¢. Extensive screening and nucleotide sequence analysis of MAb-selected clones from library Ph.D.12â„¢) failed to yield a consensus sequence.
Pepscan analyses were performed using the recently developed suspension array technology (SAT). This was used to map the recognition sites of MAbs and serum samples onto a panel of overlapping synthetic peptides (12mers) that mimicked the betanodavirus coat protein. The results of pepscan analyses required careful interpretation due to the binding of antibodies and serum samples to multiple peptides. However, three regions of the nodavirus coat protein were identified as containing B-cell epitopes: amino acids 1-50, 141-162, and 181-212. These results are discussed in relation to previous studies of immune responses to betanodaviruses, and to the future development of betanodavirus vaccines and diagnostic reagents
Short-lived solar burst spectral component at f approximately 100 GHz
A new kind of burst emission component was discovered, exhibiting fast and distinct pulses (approx. 60 ms durations), with spectral peak emission at f approx. 100 GHz, and onset time coincident to hard X-rays to within approx. 128 ms. These features pose serious constraints for the interpretation using current models. One suggestion assumes the f approx. 100 GHz pulses emission by synchrotron mechanism of electrons accelerated to ultrarelativistic energies. The hard X-rays originate from inverse Compton scattering of the electrons on the synchrotron photons. Several crucial observational tests are needed for the understanding of the phenomenon, requiring high sensitivity and high time resolution (approx. 1 ms) simultaneous to high spatial resolution (0.1 arcsec) at f approx. 110 GHz and hard X-rays
Teacher training on the implementation of science research projects in classroom context
Teacher Training on the Implementation of Science Research Projects In Classroom Contextinfo:eu-repo/semantics/publishedVersio
Feiras de ciências nas escolas portuguesas
Os programas curriculares portugueses das ciências experimentais estão orientados para contemplar aprendizagens anteriormente adquiridas e remetem para um ensino prático e investigativo, esperando relacionar a Ciência, a Tecnologia e as suas aplicações práticas. Porém, um currÃculo, por si só, não é suficiente para o sucesso do ensino. Neste contexto, pretendemos aqui demonstrar a eficácia das Feiras de Ciência, já reconhecida em vários paÃses pela sua relevância pedagógica e cultural, como uma forma alternativa que não substitui o trabalho feito no contexto de sala de aula mas que permite dar um contributo para que os alunos adquiram competências para atingirem melhores resultados. Para testar a sua aplicabilidade nas nossas escolas, foi desenvolvido um estudo durante 4 anos, com alunos de 2 e 3 ciclo. O estudo incluiu a análise da evolução da participação dos alunos, bem como a sua opinião acerca das Feiras de Ciência que participaram na sua escola
1st Hands-on Science Science Fair
1st Hands-on Science Science Fairinfo:eu-repo/semantics/publishedVersio
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