Reionization constraints using Principal Component Analysis

Using a semi-analytical model developed by Choudhury & Ferrara (2005) we study the observational constraints on reionization via a principal component analysis (PCA). Assuming that reionization at z>6 is primarily driven by stellar sources, we decompose the unknown function N_{ion}(z), representing the number of photons in the IGM per baryon in collapsed objects, into its principal components and constrain the latter using the photoionization rate obtained from Ly-alpha forest Gunn-Peterson optical depth, the WMAP7 electron scattering optical depth and the redshift distribution of Lyman-limit systems at z \sim 3.5. The main findings of our analysis are: (i) It is sufficient to model N_{ion}(z) over the redshift range 2<z<14 using 5 parameters to extract the maximum information contained within the data. (ii) All quantities related to reionization can be severely constrained for z<6 because of a large number of data points whereas constraints at z>6 are relatively loose. (iii) The weak constraints on N_{ion}(z) at z>6 do not allow to disentangle different feedback models with present data. There is a clear indication that N_{ion}(z) must increase at z>6, thus ruling out reionization by a single stellar population with non-evolving IMF, and/or star-forming efficiency, and/or photon escape fraction. The data allows for non-monotonic N_{ion}(z) which may contain sharp features around z \sim 7. (iv) The PCA implies that reionization must be 99% completed between 5.8<z<10.3 (95% confidence level) and is expected to be 50% complete at z \approx 9.5-12. With future data sets, like those obtained by Planck, the z>6 constraints will be significantly improved.Comment: Accepted in MNRAS. Revised to match the accepted versio

Developing an Adeno-Associated Viral Vector (AAV) Toolbox for CNS Gene Therapy: A Dissertation

Neurological disorders – disorders of the brain, spine and associated nerves – are a leading contributor to global disease burden with a sizable economic cost. Adeno-associated viral (AAV) vectors have emerged as an effective platform for CNS gene therapy and have shown early promise in clinical trials. These trials involve direct infusion into brain parenchyma, an approach that may be suboptimal for treatment of neurodegenerative disorders, which often involve more than a single structure in the CNS. However, overall neuronal transduction efficiency of vectors derived from naturally occurring AAV capsids after systemic administration is relatively low. We have developed novel capsids AAV-AS and AAV-B1 that lead to widespread gene delivery throughout the brain and spinal cord, particularly to neuronal populations. Both transduce the adult mouse brain \u3e10-fold more efficiently than the clinical gold standard AAV9 upon intravascular infusion, with gene transfer to multiple neuronal sub-populations. These vectors are also capable of neuronal transduction in a normal cat. We have demonstrated the efficacy of AAV-AS in the context of Huntington\u27s disease by knocking down huntingtin mRNA 33-50% after a single intravenous injection, which is better than what can be achieved by AAV9 at the particular dose. AAVB1 additionally transduces muscle, beta cells, pulmonary alveoli and retinal vasculature at high efficiency, and has reduced sensitivity to neutralizing antibodies in human sera. Generation of this vector toolbox represents a major step towards gaining genetic access to the entire CNS, and provides a platform to develop new gene therapies for neurodegenerative disorders

Dark matter, extra-terrestrial gamma-rays and the MSSM: a viability study

We fit the $\gamma$-ray excess from the galactic centre (GC) in terms of parameters of the minimal supersymmetric standard model (MSSM). Consistency with other $\gamma$-ray observation, such as those from dwarf spheroidal galaxies, is also ensured, in addition to the constraints from direct dark matter search. Furthermore, we expect the contribution to the relic density from the MSSM dark mater candidate, namely, the lightest neutralino, should not go below the stipulated value; otherwise it will amount to going beyond the MSSM by including some additional dark matter source. After a detailed scan of the parameter space in terms of four representative types of particle spectra, we identify the ones that are best fit to the observed data. However, these two are somewhat unsatisfactory in terms of $\chi^2_{min}$ as well as $p$-values. In some case(s), the unacceptability of low-$\chi^2_{min}$ regions due to direct search constraint is responsible for this. In others, the observed shape of the $\gamma$-ray spectrum makes the fits unsatisfactory. The imposed lower limit on relic density, too, has a role to play all along. On the whole, the conclusion is that the MSSM is not a very satisfactory fit for the GC $\gamma$-ray compounded with other cosmological observations and direct search limits.Comment: 40 pages, 16 figures: figures corrected, typos corrected, matches with version published in JCA

Development and Validation of Semantic Differential Scale to Assess Teachers Belief Towards Socially Disadvantaged Students

This paper intended to record the process of developing and validating a Semantic Differential Scale to assess the teacher’s belief on socially disadvantaged students in the Indian context. Social Identity Theory (SIT) and Stereotype Content Model (SCM) has been adopted. Following the new method of developing SDS proposed by Ding et al. (2008), the process resulted in a 15-item scale with a three-factorial structure. The reliability and validity of the scale according to the new method were tested with SPSS 26 and Amos 26, with Cronbach’s alpha reliability coefficients greater than 0.962. With good indices on reliability and validity, the instrument is likely to be useful to both academicians and practitioners interested in assessing the addressed context

Non-perturbative ⟨ϕ⟩\langle \phi \rangle, ⟨ϕ2⟩\langle \phi^2 \rangle and the dynamically generated scalar mass with Yukawa interaction in the inflationary de Sitter spacetime

We consider a massless minimally coupled self interacting quantum scalar field coupled to fermion via the Yukawa interaction, in the inflationary de Sitter background. The fermion is also taken to be massless and the scalar potential is taken to be a hybrid, $V(\phi)= \lambda \phi^4/4!+ \beta \phi^3/3!$ ($\lambda >0$). The chief physical motivation behind this choice of $V(\phi)$ corresponds to, apart from its boundedness from below property, the fact that shape wise $V(\phi)$ has qualitative similarity with standard inflationary classical slow roll potentials. Also, its vacuum expectation value can be negative, suggesting some screening of the inflationary cosmological constant. We choose that $\langle \phi \rangle\sim 0$ at early times with respect to the Bunch-Davies vacuum, so that perturbation theory is valid initially. We consider the equations satisfied by $\langle \phi (t) \rangle$ and $\langle \phi^2(t) \rangle$, constructed from the coarse grained equation of motion for the slowly rolling $\phi$. We then compute the vacuum expectation values of various relevant operators using the in-in formalism up to three loop, in terms of the leading powers of the secular logarithms. For a closed fermion loop, we have restricted ourselves here to only the local contribution. These large logarithms are then resummed by constructing suitable non-perturbative equations to compute $\langle \phi \rangle$ and $\langle \phi^2 \rangle$. $\langle \phi \rangle$ turns out to be at least approximately an order of magnitude less compared to the minimum of the classical potentail, $-3\beta/\lambda$, owing to the strong quantum fluctuations. For $\langle \phi^2 \rangle$, we have computed the dynamically generated scalar mass at late times, by taking the appropriate purely local constributions. Variations of these quantities with respect to different couplings have also been presented.Comment: v1; 34pp, 10 figue