Hamiltonian Formalism of the de-Sitter Invariant Special Relativity

Lagrangian of the Einstein's special relativity with universal parameter $c$ ($\mathcal{SR}_c$) is invariant under Poincar\'e transformation which preserves Lorentz metric $\eta_{\mu\nu}$. The $\mathcal{SR}_c$ has been extended to be one which is invariant under de Sitter transformation that preserves so called Beltrami metric $B_{\mu\nu}$. There are two universal parameters $c$ and $R$ in this Special Relativity (denote it as $\mathcal{SR}_{cR}$). The Lagrangian-Hamiltonian formulism of $\mathcal{SR}_{cR}$ is formulated in this paper. The canonic energy, canonic momenta, and 10 Noether charges corresponding to the space-time's de Sitter symmetry are derived. The canonical quantization of the mechanics for $\mathcal{SR}_{cR}$-free particle is performed. The physics related to it is discussed.Comment: 24 pages, no figur

The rare decays B --> K(*) anti-K(*) and R-parity violating supersymmetry

We study the branching ratios, the direct CP asymmetries in $B\to K^{(*)}\bar{K}^{(*)}$ decays and the polarization fractions of $B\to K^{*}\bar{K}^{*}$ decays by employing the QCD factorization in the minimal supersymmetric standard model with R-parity violation. We derive the new upper bounds on the relevant R-parity violating couplings from the latest experimental data of $B\to K^{(*)}\bar{K}^{(*)}$, and some of these constraints are stronger than the existing bounds. Using the constrained parameter spaces, we predict the R-parity violating effects on the other quantities in $B\to K^{(*)}\bar{K}^{(*)}$ decays which have not been measured yet. We find that the R-parity violating effects on the branching ratios and the direct $CP$ asymmetries could be large, nevertheless their effects on the longitudinal polarizations of $B\to K^{*}\bar{K}^{*}$ decays are small. Near future experiments can test these predictions and shrink the parameter spaces.Comment: 31 pages with 10 figure

Expression of Notch-1 receptor and its ligands Jagged-1 and Delta-1 in amoeboid microglia in postnatal rat brain and murine BV-2 cells.

Notch-1 receptor signaling pathway is involved in neuronal and glial differentiation. Its involvement in microglial functions, however, has remained elusive. This study reports the localization of Notch-1 receptor immunoreactivity in the amoeboid microglial cells (AMC) in the postnatal rat brain. By immunofluorescence, Notch-1 receptor was colocalized with its ligands, Jagged-1 and Delta-1, in the AMC in the corpus callosum and subventricular zone. Notch-1 immunopositive cells were confirmed to be microglia labeled by OX42 and lectin. Immunoexpression of Notch-1 receptor was progressively reduced with age. Western blot analysis showed that Notch-1 protein level in the corpus callosum in which the AMC were heavily populated was concomitantly decreased. In postnatal rats challenged with lipopolysaccharide (LPS), Notch-1 receptor immunofluorescence in AMC was noticeably enhanced. Furthermore, Notch-1 protein level in the corpus callosum was increased as revealed by Western blotting analysis. In primary microglial culture treated with LPS, mRNA expression of Notch-1 and its ligand Jagged-1 was upregulated but that of Delta-1 was reduced. The expression pattern of Notch-1 and its ligands was confirmed in murine BV-2 cells. Furthermore, Notch-1 neutralization with its antibody reduced its protein expression. More importantly, neutralization of Notch-1 concomitantly suppressed the mRNA expression of IL-6, IL-1, M-CSF, and iNOS; TNF-α, mRNA expression, however, was enhanced. Western blot confirmed the changes of protein level of the above except for IL-6, which remained relatively unaltered. It is concluded that Notch-1 signaling in the AMC and LPS-activated microglia/BV-2 cells modulates the expression of proinflammatory cytokines and nitric oxide

Intrinsic thermal vibrations of suspended doubly clamped single-wall carbon nanotubes

We report the observation of thermally driven mechanical vibrations of suspended doubly clamped carbon nanotubes, grown by chemical vapor deposition (CVD). Several experimental procedures are used to suspend carbon nanotubes. The vibration is observed as a blurring in images taken with a scanning electron microscope. The measured vibration amplitudes are compared with a model based on linear continuum mechanics.Comment: pdf including figures, see: http://www.unibas.ch/phys-meso/Research/Papers/2003/NT-Thermal-Vibrations.pd

Bosonized noncommutative bi-fundamental fermion and S-duality

We perform the path-integral bosonization of the recently proposed noncommutative massive Thirring model (NCMT$_{1}$) [JHEP0503(2005)037]. This model presents two types of current-current interaction terms related to the bi-fundamental representation of the group U(1). Firstly, we address the bosonization of a bi-fundamental free Dirac fermion defined on a noncommutative (NC) Euclidean plane \IR_{\theta}^{2}. In this case we show that the fermion system is dual to two copies of the NC Wess-Zumino-Novikov-Witten model. Next, we apply the bosonization prescription to the NCMT$_{1}$ model living on \IR_{\theta}^{2} and show that this model is equivalent to two-copies of the WZNW model and a two-field potential defined for scalar fields corresponding to the global $U(1)\times U(1)$ symmetry plus additional bosonized terms for the four fermion interactions. The bosonic sector resembles to the one proposed by Lechtenfeld et al. [Nucl. Phys. B705(2005)477] as the noncommutative sine-Gordon for a {\sl pair} of scalar fields. The bosonic and fermionic couplings are related by a strong-weak duality. We show that the couplings of the both sectors for some representations satisfy similar relationships up to relevant re-scalings, thus the NC bi-fundamental couplings are two times the corresponding ones of the NC fundamental (anti-fundamental) and eight times the couplings of the ordinary massive Thirring and sine-Gordon models.Comment: 18 pages, LaTex. References added. A general product $f(x-vt) \star g(x-vt)$ has been considered in the conclusion section . Version to appear in JHE

Supersymmetric probes on the conifold

We study the supersymmetric embeddings of different D-brane probes in the AdS_5 x T^{1,1} geometry. The main tool employed is kappa symmetry and the cases studied include D3-, D5- and D7-branes. We find a family of three-cycles of the T^{1,1} space over which a D3-brane can be wrapped supersymmetrically and we determine the field content of the corresponding gauge theory duals. Supersymmetric configurations of D5-branes wrapping a two-cycle and of spacetime filling D7-branes are also found. The configurations in which the entire T^{1,1} space is wrapped by a D5-brane (baryon vertex) and a D7-brane are also studied. Some other embeddings which break supersymmetry but are nevertheless stable are also determined.Comment: 44 pages, LaTeX; v2: typos corrected, references added, discussion of D5-brane embeddings improve

Octet baryon electromagnetic form factors in nuclear medium

We study the octet baryon electromagnetic form factors in nuclear matter using the covariant spectator quark model extended to the nuclear matter regime. The parameters of the model in vacuum are fixed by the study of the octet baryon electromagnetic form factors. In nuclear matter the changes in hadron properties are calculated by including the relevant hadron masses and the modification of the pion-baryon coupling constants calculated in the quark-meson coupling model. In nuclear matter the magnetic form factors of the octet baryons are enhanced in the low $Q^2$ region, while the electric form factors show a more rapid variation with $Q^2$. The results are compared with the modification of the bound proton electromagnetic form factors observed at Jefferson Lab. In addition, the corresponding changes for the bound neutron are predicted.Comment: Version accepted for publication in J.Phys. G. Few changes. 40 pages, 14 figures and 8 table

The impact of stellar metallicity on rotation and activity evolution in the Kepler field using gyro-kinematic ages

In recent years, there has been a push to understand how chemical composition affects the magnetic activity levels of main sequence low-mass stars. Results indicate that more metal-rich stars are more magnetically active for a given stellar mass and rotation period. This metallicity dependence has implications for how the rotation periods and activity levels of low-mass stars evolve over their lifetimes. Numerical modelling suggests that at late ages more metal-rich stars should be rotating more slowly and be more magnetically active. In this work, we study the rotation and activity evolution of low-mass stars using a sample of Kepler field stars. We use the gyro-kinematic age dating technique to estimate ages for our sample and use the photometric activity index as our proxy for magnetic activity. We find clear evidence that, at late ages, more metal-rich stars have spun down to slower rotation in agreement with the theoretical modeling. However, further investigation is required to definitively determine whether the magnetic activity evolution occurs in a metallicity dependent way.Comment: 10 pages, 9 figures. This paper has undergone peer review at MNRAS with only a very minor revision requested in the last round of comment

Do academically selective school systems strengthen the link between students’ family backgrounds and the likelihood of higher education participation?

Proponents of academic selection argue that academic selection helps children from disadvantaged backgrounds have better lifelong outcomes. However, the evidence needs to be clarified since selections by performance could be a proxy for selection by socioeconomic class. Based on the unique situation in England, where both selective and non-selective systems coexist, we evaluate whether students from selective schools are more likely to continue higher education than those in non-selective schools and whether the link between students’ family backgrounds and their likelihood of higher education participation is stronger under a selective system. The results show that attending selective schools is associated with some post-18 advantages for pupils who stayed until the end of Key Stage 5, but brings disadvantages for those who left at earlier stages, even if we look at the upper bound of the selective school effect. Meanwhile, the link between students’ family backgrounds and future opportunities is consistently stronger under the selective system

Is technology always helpful?: A critical review of the impact on learning outcomes of education technology in supporting formative assessment in schools

While education technology has been widely used in classrooms, and considerable investments have been made to support its use in the UK, the evidence base for many such rapidly changing technologies is weak, and their efficacy is unclear. The aim of this paper is to systematically review and synthesise empirical research on the use of technology in formative assessment, to identify approaches that are effective in improving pupils’ learning outcomes. The review involved a search of 11 major databases, and included 55 eligible studies. The results suggest promising evidence that digitally delivered formative assessment could facilitate the learning of maths and reading for young children, but there is no good evidence that it is effective for other subjects, or for older children, or that it is any more effective than formative assessment without technology. The review found no good evidence that learner response systems work in enhancing children’s academic attainment, and there is no evidence supporting the effectiveness of such technologies that embed gaming features. Much research in this area is of poor quality. More rigorous studies using causal designs are thus urgently needed. Meantime, there should be no rush to use technology on the basis of improving attainment