arXiv subjects

Rhiju Das

Publications and source records attributed to Rhiju Das.

22 records · Page 2Linked to original sources

arXiv2011

Why Can't We Predict RNA Structure At Atomic Resolution?

No existing algorithm can start with arbitrary RNA sequences and return the precise, three-dimensional structures that ensures their biological function. This chapter outlines current algorithms for automated RNA structure prediction (including our own FARNA-FARFAR), highlights their successes, and dissects their limitations, using a tetraloop and the sarcin/ricin motif as examples. The barriers to future advances are considered in light of three particular challenges: improving computational sampling, reducing reliance on experimentally solved structures, and avoiding coarse-grained representations of atomic-level interactions. To help meet these challenges and better understand the current state of the field, we propose an ongoing community-wide CASP-style experiment for evaluating the performance of current structure prediction algorithms.

q-bio.BM↗

arXiv2003

A measurement of H_0 from Ryle Telescope, ASCA and ROSAT observations of Abell 773

We present new Ryle Telescope (RT) observations of the Sunyaev Zel'dovich (SZ) decrement from the cluster Abell 773. The field contains a number of faint radio sources that required careful subtraction. We use ASCA observations to measure the gas temperature and a ROSAT HRI image to model the gas distribution. Normalising the gas distribution to fit the RT visibilities returns a value of H_0 of 77 (+19,-15) km/s/Mpc (1-sigma errors) for an Einstein-de-Sitter universe, or 85 (+20,-17) km/s/Mpc for a flat model with Omega_Lambda = 0.7. The errors quoted include estimates of the effects of the principal errors: noise in the SZ measurement, gas temperature uncertainty, and line-of sight depth uncertainty.

astro-ph↗

arXiv2001

Detection of a CMB decrement towards a cluster of mJy radiosources

We present the results of radio, optical and near-infrared observations of the field of TOC J0233.3+3021, a cluster of milliJansky radiosources from the TexOx Cluster survey. In an observation of this field with the Ryle Telescope (RT) at 15 GHz, we measure a decrement in the cosmic microwave background (CMB) of $-675 \pm 95 μ$Jy on the RT's $\approx$ 0.65 k$λ$ baseline. Using optical and infrared imaging with the McDonald 2.7-m Smith Reflector, Calar Alto 3.5-m telescope and UKIRT, we identify the host galaxies of five of the radiosources and measure magnitudes of $R \approx 24$, $J \approx 20$, $K \approx 18$. The CMB decrement is consistent with the Sunyaev-Zel'dovich (SZ) effect of a massive cluster of galaxies, which if modelled as a spherical King profile of core radius $θ_C = 20^{\prime\prime}$ has a central temperature decrement of $900 μ$K. The magnitudes and colours of the galaxies are consistent with those of old ellipticals at $z \sim 1$. We therefore conclude that TOC J0233.3+3021 is a massive, high redshift cluster. These observations add to the growing evidence for a significant population of massive clusters at high redshift, and demonstrate the effectiveness of combining searches for AGN `signposts' to clusters with the redshift-independence of the SZ effect.

astro-ph↗

arXiv2001

A maximum-likelihood approach to removing radio sources from SZ observations, with application to Abell 611

We describe a maximum-likelihood technique for the removal of contaminating radio sources from interferometric observations of the Sunyaev-Zel'dovich (SZ) effect. This technique, based on a simultaneous fit for the radio sources and extended SZ emission, is also compared to techniques previously applied to Ryle Telescope observations and is found to be robust. The technique is then applied to new observations of the cluster Abell 611, and a decrement of -540 +/- 125 microJy/beam is found. This is combined with a ROSAT HRI image and a published ASCA temperature to give an Hubble constant estimate of 52+24-16 km/s/Mpc.

astro-ph↗