An Imaging Fabry-Perot System for the Robert Stobie Spectrograph on the Southern African Large Telescope

We present the design of the Fabry-Perot system of the Robert Stobie Spectrograph on the 10-meter class Southern African Large Telescope and its characterization as measured in the laboratory. This system provides spectroscopic imaging at any desired wavelength spanning a bandpass 430 - 860 nm, at four different spectral resolving powers ranging from 300 to 9000. Our laboratory tests revealed a wavelength dependence of the etalon gap and parallelism with a maximum variation between 600 - 720 nm that arises because of the complex structure of the broadband multi-layer dielectric coatings. We also report an unanticipated optical effect of this multi-layer coating structure that produces a significant, and wavelength dependent, change in the apparent shape of the etalon plates. This change is caused by two effects: the physical non-uniformities or thickness variations in the coating layers, and the wavelength dependence of the phase change upon refection that can amplify these non-uniformities. We discuss the impact of these coating effects on the resolving power, finesse, and throughput of the system. This Fabry-Perot system will provide a powerful tool for imaging spectroscopy on one of the world's largest telescopes.Comment: 17 pages, 14 figures, accepted for publication in The Astronomical Journa

The unfriendly ISM in the radio galaxy 4C12.50 (PKS 1345+12)

The radio source 4C12.50 has often been suggested to be a prime candidate for the link between ultraluminous infrared galaxies and young radio galaxies. A VLBI study of the neutral hydrogen in the nuclear regions of this object shows that most of the gas detected close to the systemic velocity is associated with an off-nuclear cloud (~50 to 100 pc from the radio core) with a column density of ~10^22 T_spin/100 K) cm^(-2) and an HI mass of a few times 10^5 to 10^6 M_sun. We consider a number of possibilities to explain the results. In particular, we discus the possibility that this cloud indicates the presence of a rich and clumpy interstellar medium in the centre, likely left over from the merger that triggered the activity and that this medium influences the growth of the radio source. The location of the cloud -- at the edge of the northern radio jet/lobe -- suggests that the radio jet might be interacting with a gas cloud. This interaction could be responsible for bending the young radio jet. The velocity profile of the gas is relatively broad (~150$ km/s) and we interpret this as kinematical evidence for interaction of the radio plasma with the cloud. We also consider the model where the cloud is part of a broader circumnuclear structure. Only a limited region of this structure would have sufficient background radio brightness and large enough column depth in neutral gas to obtain detectable HI absorption against the counterjet. The VLBI study of the neutral hydrogen in 4C12.50 suggests that HI detected near the systemic velocity (as it is often the case in radio galaxies) may not necessarily be connected with a circumnuclear disk or torus (as is very often assumed) but instead could be a tracer of the large-scale medium that surrounds the active nucleus and that may influence the growth of the young radio source.Comment: 7 pages, 2 figures. Accepted for publication in A&

Probing radio source environments via HI and OH absorption

We present the results of HI and OH absorption measurements towards a sample of radio sources using the Arecibo 305-m telescope and the GMRT. In total, 27 radio sources were searched for associated 21-cm HI absorption. One totally new HI absorption system was detected against the radio galaxy 3C258, while five previously known HI absorption systems, and one galaxy detected in emission, were studied with improved frequency resolution and/or sensitivity. Our sample included 17 GPS and CSS objects, 4 of which exhibit HI absorption. This detection rate of ~25% compares with a value of ~40% by Vermeulen et al. for similar sources. We detected neither OH emission nor absorption towards any of the sources that were observed at Arecibo, and estimate a limit on the abundance ratio of N(HI)/N(OH)>4x10^6 for 3C258. We have combined our results with those from other available HI searches to compile a heterogeneous sample of 96 radio sources consisting of 27 GPS, 35 CSS, 13 flat spectrum and 21 large sources. The HI absorption detection rate is highest (~45%) for the GPS sources and least for the large sources. We find HI column density to be anticorrelated with source size, as reported earlier by Pihlstr\"om et al. The HI column density shows no significant dependence on either redshift or luminosity, which are themselves strongly correlated. These results suggest that the environments of radio sources on GPS/CSS scales are similar at different redshifts. Further, in accordance with the unification scheme, the GPS/CSS galaxies have an HI detection rate of ~40% which is significantly higher than the detection rate (~20%) towards the GPS/CSS quasars. Also, the principal (strongest) absorption component detected towards GPS sources appears blue-shifted in ~65% of the cases, in agreement with the growing evidence for jet-cloud interactions.Comment: Abridged abstract, 22 pages, 21 figures, moderately revised, accepted for publication in MNRA

Endothelial and Inflammation Biomarker Profiles at Diagnosis Reflecting Clinical Heterogeneity and Serving as a Prognostic Tool For Treatment Response in Two Independent Cohorts of Patients With Juvenile Dermatomyositis

Objective: Juvenile dermatomyositis (DM) is a heterogeneous systemic immune-mediated vasculopathy. This study was undertaken to 1) identify inflammation/endothelial dysfunction–related biomarker profiles reflecting disease severity at diagnosis, and 2) establish whether such biomarker profiles could be used for predicting the response to treatment in patients with juvenile DM. Methods: In total, 39 biomarkers related to activation of endothelial

Energy band diagram of device-grade silicon nanocrystals

This work was supported by the EPSRC (EP/K022237/1) and the Leverhulme International Network (IN-2012-136). SA would like to acknowledge the support of the Ulster University Vice-Chancellor's Research Studentship and CR that of the NI-DEL studentship.Device grade silicon nanocrystals (NCs) are synthesized using an atmospheric-pressure plasma technique. The Si NCs have a small and well defined size of about 2.3 nm. The synthesis system allows for the direct creation of thin films, enabling a range of measurements to be performed and easy implementation of this material in different devices. The chemical stability of the Si NCs is evaluated, showing relatively long-term durability thanks to hydrogen surface terminations. Optical and electrical characterization techniques, including Kelvin probe, ultraviolet photoemission spectroscopy and Mott-Schottky analysis, are employed to determine the energy band diagram of the Si NCs.Publisher PDFPeer reviewe

Corn nitrogen rate recommendation tools’ performance across eight US midwest corn belt states

Determining which corn (Zea mays L.) N fertilizer rate recommendation tools best predict crop N need would be valuable for maximizing profits and minimizing environmental consequences. Simultaneous comparisons of multiple tools across various environmental conditions have been limited. The objectives of this research were to evaluate the performance of publicly‐available N fertilizer recommendation tools across diverse soil and weather conditions for: (i) prescribing N rates for planting and split‐fertilizer applications, and (ii) economic and environmental effects. Corn N‐response trials using standardized methods were conducted at 49 sites, spanning eight US Midwest states and three growing seasons. Nitrogen applications included eight rates in 45 kg N ha−1 increments all at‐planting and matching rates with 45 kg N ha−1 at‐planting plus at the V9 development stage. Tool performances were compared to the economically optimal N rate (EONR). Over this large geographic region, only 10 of 31 recommendation tools (mainly soil nitrate tests) produced N rate recommendations that weakly correlated to EONR (P ≤ .10; r2 ≤ .20). With other metrics of performance, the Maximum Return to N (MRTN) soil nitrate tests, and canopy reflectance sensing came close to matching EONR. Economically, all tools but the Maize‐N crop growth model had similar returns compared to EONR. Environmentally, yield goal based tools resulted in the highest environmental costs. Results show that no tool was universally reliable over this study\u27s diverse growing environments, suggesting that additional tool development is needed to better represent N inputs and crop utilization at a larger regional level

Commandeering a biological pathway using aptamer-derived molecular adaptors

Induction of molecular proximity can mediate a discrete functional response in biological systems. Therefore, creating new and specific connectivity between non-interacting proteins is a means of imposing rational control over biological processes. According to this principle, here we use composite RNA aptamers to generate molecular adaptors that link various ‘target’ molecules to a common ‘utility’ molecule, with the utility molecule being an entry point to a pathway conscripted to process the target molecule. In particular, we created a bi-functional aptamer that simultaneously binds to the green fluorescent protein (serving as a surrogate extracellular target) and the opsonin C3b/iC3b (serving as the utility molecule). This bi-functional aptamer enabled us to commandeer the C3-based opsonization-phagocytosis pathway to selectively transport an extracellular target into the lysosome for degradation. This novel strategy has the potential for powerful therapeutic applications with extracellular proteins involved in tumor development or surface markers on cancer cells as the target molecules