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The Murchison Widefield Array: The Square Kilometre Array Precursor at Low Radio Frequencies
No full textRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)The Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the mid-west of Western Australia, a location chosen for its extremely low levels of radio frequency interference. The MWA operates at low radio frequencies, 80–300 MHz, with a processed bandwidth of 30.72 MHz for both linear polarisations, and consists of 128 aperture arrays (known as tiles) distributed over a ~3-km diameter area. Novel hybrid hardware/software correlation and a real-time imaging and calibration systems comprise the MWA signal processing backend. In this paper, the as-built MWA is described both at a system and sub-system level, the expected performance of the array is presented, and the science goals of the instrument are summarised
Digital scholarship and resource sharing among astronomy libraries: a case study of RRI library.
No full textRestricted AccessPrior to developing consortia, astronomy libraries in India were in an embryonic stage
with meager resources and dwindling budgets. It was extremely difficult for them to respond to
the needs of their users. Librarians at the various Indian astronomy institutes were forced to look
at alternate strategies. Raman Research Institute in Bangalore will be examined in a case study where they attempt to implement resource sharing with other institutes in India and how they were able to provide efficient service to the astronomy community
Correlated Spatio-Temporal Fluctuations in Chromatin Compaction States Characterize Stem Cells
No full textRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)Stem cells integrate signals from the microenvironment to generate lineage-specific gene expression programs upon differentiation. Undifferentiated cell nuclei are easily deformable, with an active transcriptome, whereas differentiated cells have stiffer nuclei and condensed chromatin. Chromatin organization in the stem cell state is known to be highly dynamic but quantitative characterizations of its plasticity are lacking. Using fluorescence imaging, we study the spatio-temporal dynamics of nuclear architecture and chromatin compaction in mouse embryonic stem (ES) cells and differentiated states. Individual ES cells exhibit a relatively narrow variation in chromatin compaction, whereas primary Mouse embryonic fibroblasts (PMEF) show broad distributions. However, spatial correlations in chromatin compaction exhibit an emergent length scale in PMEFs, although they are unstructured and longer ranged in ES cells. We provide evidence for correlated fluctuations with large amplitude and long intrinsic timescales, including an oscillatory component, in both chromatin compaction and nuclear area in ES cells. Such fluctuations are largely frozen in PMEF. The role of actin and Lamin A/C in modulating these fluctuations is described. A simple theoretical formulation reproduces the observed dynamics. Our results suggest that, in addition to nuclear plasticity, correlated spatio-temporal structural fluctuations of chromatin in undifferentiated cells characterize the stem cell state
Work fluctuations for a Brownian particle in a harmonic trap with fluctuating locations
No full textopen Access.We consider a Brownian particle in a harmonic trap. The location of the trap is modulated according to an Ornstein-Uhlenbeck process. We investigate the fluctuation of the work done by the modulated trap on the Brownian particle in a given time interval in the steady state. We compute the large deviation as well as the complete asymptotic form of the probability density function of the work done. The theoretical asymptotic forms of the probability density function are in very good agreement with the numerics. We also discuss the validity of the fluctuation theorem for this system
Temperature-dependent electron mobility in InAs nanowires
No full textRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)Effective electron mobilities are obtained by transport measurements on InAs nanowire field-effect transistors at temperatures ranging from 10 to 200 K. The mobility increases with temperatures below ~30–50 K, and then decreases with temperatures above 50 K, consistent with other reports. The magnitude and temperature dependence of the observed mobility can be explained by Coulomb scattering from ionized surface states at typical densities. The behaviour above 50 K is ascribed to the thermally activated increase in the number of scatterers, although nanoscale confinement also plays a role as higher radial subbands are populated, leading to interband scattering and a shift of the carrier distribution closer to the surface. Scattering rate calculations using finite-element simulations of the nanowire transistor confirm that these mechanisms are able to explain the data
Electronic Theses and Dissertation (ETD) achives at Raman Research Institute: An Overview
No full textRestricted Access Book chapter from Proceedings of ICKMODE-2013 Conference, held at SIT, Tumkur, Karnataka, India from 17th to 19th January 2013. Ed by Shekar Hp et al, 2013. page- 349.An arch motive of e-Theses is to make the research and scholarship conducted by graduate students readily accessible, and for the long-term archiving. The RRI library was established in 1979. The e-Theses archive is for full-text electronic copies of theses produced by research graduates from the Institute. It is an Open Access database aiming to make the material avail-able to the widest possible Academia. The RRI Library has a collection of theses in the Re-search areas of Astronomy & Astrophysics, Soft Condensed Matter, Theoretical Physics, Light and Matter Physics and these are the core subject branches students perform the research and produce the doctoral thesis. The Research and Educational Institutes, Universities, play a major role in the generation and dissemination of knowledge by facilitating research work and producing Ph.D. thesis. This product of Doctoral Dissertation becomes precious and a rare source of information. ETD database of the institute showcases its academic output on a single platform, which provide wider visibility and enhances the prestige of the Institute. It acts as a catalyst to the quality of research and helps in attracting new students and research scholars
Enhanced stability of the columnar matrix in a discotic liquid crystal by insertion of ZnO nanoparticles
No full textRestricted Access.An experimental characterisation of dispersions of ZnO nanoparticles (NPs) in the columnar matrix of a discotic liquid crystal has been carried out. Thermophysical properties have been investigated by absorbance spectroscopy, differential scanning calorimetry, polarising optical microscopy, dielectric measurements, dc conductivity, X-ray diffraction and infrared (IR) dichroism technique. The experimental results show that inclusion of ZnO NPs into the columnar matrix enhances the orientational order in the columnar phase and does not affect the two-dimensional hexagonal lattice. The alignment in homeotropic samples is also found to be better with the addition of the NPs. The real (ϵ′) and imaginary parts (ϵ′′) of the permittivity increase by a small amount in the dispersions. The order parameter measured using the IR dichroism technique in the face-on geometry (homeotropic alignment) shows an enhancement for the composite system. The dc conductivity is also found to increase by an order of magnitude by addition of the NPs. These results suggest an improved stacking of the disc-like molecules within the columns by the insertion of the ZnO NPs possessing high charge mobility. Such composite systems would be highly beneficial for potential applications such as organic conductors
The EoR sensitivity of the Murchison widefield array
No full textRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)Using the final 128 antenna locations of the Murchison Widefield Array (MWA), we calculate its sensitivity to the epoch of reionization (EoR) power spectrum of redshifted 21 cm emission for a fiducial model and provide the tools to calculate the sensitivity for any model. Our calculation takes into account synthesis rotation, chromatic and asymmetrical baseline effects, and excludes modes that will be contaminated by foreground subtraction. For the fiducial model, the MWA will be capable of a 14σ detection of the EoR signal with one full season of observation on two fields (900 and 700 h